In healthcare, the weekend effect is the finding of a difference in mortality rate for patients admitted to hospital for treatment at the weekend compared to those admitted on a weekday. The effects of the weekend on patient outcomes has been a concern since the late 1970s, and a ‘weekend effect’ is now well documented. Although this is a controversial area, the balance of opinion is that the weekend (and bank holidays) have a deleterious effect on patient care (and specifically increase mortality)—based on the larger studies that have been carried out. Variations in the outcomes for patients treated for many acute and chronic conditions have been studied.
- 1 Published research: Non-disease specific (unselected) patients
- 2 Published research: Disease-specific (selected) patients: Cardiorespiratory medicine
- 3 Published research: Disease-specific (selected) patients: Gastroenterology, nephrology and other medical specialties
- 4 Published research: Disease-specific (selected) patients: neuroscience
- 5 Published research: Disease-specific (selected) patients: Paediatrics and obstetrics
- 6 Published research: Disease-specific (selected) patients: Specialist surgery
- 7 Published research: Summary
- 8 Published research: Discussion
- 9 Cause of weekend effect
- 10 Weekend effect and working patterns
- 11 Politics
- 12 References
Published research: Non-disease specific (unselected) patientsEdit
Schmulewitz et al., in the UK in 2005, studied 3,244 patients with chronic obstructive pulmonary disease, cerebrovascular accidents, pulmonary embolism, pneumonia, collapse and upper gastrointestinal bleed. They found "Weekend admission was not associated with significantly higher in-hospital mortality, readmission rates or increased length of stay compared to the weekday equivalent for any of the six conditions".
However, in 2010, Clarke et al., in a much larger Australian study of 54,625 mixed medical/surgical non-elective admissions showed a significant weekend effect (i.e. worse mortality) for acute myocardial infarction. Marco et al. (2011), in a US study of 429,880 internal medical admissions showed that death within 2 days after admission was significantly higher for a weekend admission, when compared to a weekday one (OR = 1.28; 95% CI = 1.22-1.33). In the same year, in an Irish study of 25,883 medical admissions (Mikulich et al.), patients admitted at the weekend had an approximate 11% increased 30-day in-hospital mortality, compared with a weekday admission; although this was not statistically significant either before or after risk adjustment. Thus the authors pointed out that "admission at the weekend was not independently predictive in a risk model that included Illness Severity (age and biochemical markers) and co-morbidity".
There is some evidence for intervention from physicians, in an attempt to address this issue. Bell et al., in 2013, surveyed 91 acute hospital sites in England to evaluate systems of consultant cover for acute medical admissions. An 'all inclusive' pattern of consultant working, incorporating all guideline recommendations (and which included the minimum consultant presence of 4 hours per day) was associated with reduced excess weekend mortality (p<0.05).
In 2014, it was shown in a huge US study, that the presence of resident trainee doctors (and nurses) may also be of benefit (Ricciardi, 2014). In this study of 48,253,968 medical patients, the relative risk of mortality was 15% higher following weekend admission as compared to weekday admission. This is currently the largest known study in this area. After adjusting for diagnosis, age, sex, race, income level, payer, comorbidity, and weekend admission, the overall odds of mortality was higher for patients in hospitals with fewer nurses and staff physicians. Mortality following a weekend admission for patients admitted to a hospital with resident trainees was significantly higher (17%) than hospitals with no resident trainees (p<0.001).
In the following year, Vest-Hansen et al.—in a whole nation study, in Denmark—studied 174,192 acute medical patients. The age-standardised and sex-standardised 30-day mortality rate was 5.1% (95% CI 5.0-5.3) after admission during weekday office hours, 5.7% (95% CI 5.5-6.0) after admission during weekday (out of hours), 6.4% (95% CI 6.1-6.7) after admission during weekend daytime hours, and 6.3% (95% CI 5.9-6.8) after admission during weekend night-time hours. In 2016, Huang et al., in Taiwan, studied 82,340 patients, admitted to the internal medicine departments of 17 medical centres. Patients admitted at the weekend had higher in-hospital mortality (OR = 1.19; 95% CI 1.09-1.30; p < 0.001).
In a 2016 study of 12 Italian Acute Medical Units, Ambrosi et al. found that elderly patients were six times (95% CI 3.6-10.8) more likely at risk of dying at weekends. They also found that "those with one or more ED admissions in the last 3 months were also at increased risk of dying (RR = 1.360, 95% CI 1.02-1.81) as well as those receiving more care from family carers (RR = 1.017, 95% CI 1.001–1.03). At the nursing care level, those patient receiving less care by Registered Nurses (RNs) at weekends were at increased risk of dying (RR = 2.236, 95% CI 1.27-3.94) while those receiving a higher skill-mix, thus indicating that more nursing care was offered by RNs instead of Nursing Auxiliaries were at less risk of dying (RR = 0.940, 95% CI = 0.91-0.97)."
Conway et al., in 2017, studied of 44,628 Irish medical patients. Weekend admissions had an increased mortality of 5.0%, compared with weekday admissions of 4.5%. Survival curves showed no mortality difference at 28 days (P = 0.21) but a difference at 90 days (P = 0.05).
The effects of the introduction of a 7-day consultant service have been investigated in medical patients. In 2015, Leong et al. studied elderly medical patients in the UK; noting admission numbers increasing from 6,304 (November 2011-July 2012) to 7,382 (November 2012-July 2013), with no change in acuity score. They stated that the "introduction of seven-day consultant working was associated with a reduction in in-hospital mortality from 11.4% to 8.8% (p<0.001)". Weekend discharges increased from general medical wards (from 13.6% to 18.8%, p<0.001) but did not increase from elderly medicine wards.
In December 2016, another study found that reports of higher weekend mortality rates were based on administrative databases with incomplete information about the clinical state of patients on admission, and that studies that used better data found no greater risk.
Non-elective (emergency) Patients There have been many similar studies (with similar conclusions) in surgery. In the US, in a very large study in 2011, 29,991,621 non-elective general surgical hospital admissions were studied (Ricciardi et al.). Inpatient mortality was reported as 2.7% for weekend and 2.3% for weekday admissions (p<0.001). Regression analysis revealed significantly higher mortality during weekends for 15 of the 26 (57.7%) major diagnostic categories. The weekend effect remained, and mortality was noted to be 10.5% higher during weekends compared with weekdays after adjusting for all other variables.
In another huge US study in 2016 (Ricciardi et al., 2016), 28,236,749 non-elective surgical patients were evaluated, with 428,685 (1.5%) experiencing one or more Patient Safety Indicator (PSI) events. The rate of PSI was the same for patients admitted on weekends as compared to weekdays (1.5%). However, the risk of mortality was 7% higher if a PSI event occurred to a patient admitted on a weekend, as compared with a weekday. In addition, compared to patients admitted on weekdays, patients admitted on weekends had a 36% higher risk of postoperative wound dehiscence, 19% greater risk of death in a low-mortality diagnostic-related group, 19% increased risk of postoperative hip fracture, and 8% elevated risk of surgical inpatient death.
Also in 2016, Ozdemir et al. studied 294,602 surgical emergency admissions to 156 NHS Trusts (hospital systems) in the UK, with a 30-day mortality of 4.2%. Trust-level mortality rates for this cohort ranged from 1.6 to 8.0%. The lowest mortality rates were observed in hospitals with higher levels of medical and nursing staffing, and a greater number of operating theatres and critical care beds relative to provider size. Higher mortality rates were seen in patients admitted to hospital at weekends [OR = 1.11; 95% CI 1.06-1.17; p<0.0001], in hospitals with fewer general surgical doctors [OR = 1.07; 95% CI 1.01-1.13; p=0.019] and with lower nursing staff ratios [OR = 1.0; 95% CI 1.01-1.13; p=0.024].
McLean et al., in the UK, also in 2016, studied 105,002 elderly (≥70 years) emergency general surgical admissions. Factors associated with increased 30-day in-hospital mortality were increasing age and Charlson score, admissions directly from clinic, operations undertaken at the weekend, and patients admitted earlier in the study period.
Elective patients The effect is not just seen in non-elective surgical patients. Aylin et al. (2013) in the UK, investigated 27,582 deaths (within 30 days) after 4,133,346 inpatient admissions for elective operating room procedures; overall crude mortality rate was 6.7 per 1000). The adjusted odds of death were 44% and 82% higher, respectively, if the procedures were carried out on a Friday (OR = 1.44, 95% CI 1.39-1.50) or a weekend (OR = 1.82, 95% CI 1.71-1.94) compared with a Monday.
In a Canadian study (McIsaac et al., 2014), 333,344 elective surgical patients were studied, of whom 2826 died within 30 days of surgery; overall crude mortality rate was 8.5 deaths per 1000. Undergoing elective surgery on the weekend was associated with a 1.96 times higher odds of 30-day mortality than weekday surgery (95% CI 1.36-2.84). This significant increase in the odds of postoperative mortality was confirmed using a multivariable logistic regression analysis (OR = 1.51; 95% CI 1.19-1.92).
Both non-elective and elective patients Mohammed et al., in 2012 in the UK, compared elective and non-elective admissions, in terms of day of admission. The mortality for non-elective patients following weekday admission was 0.52% (7,276/1,407,705), compared with 0.77% (986/127,562) following weekend admission. Of the 3,105,249 emergency admissions, 76.3% (2,369,316) were admitted on a weekday and 23.7% (735,933) were admitted at the weekend. The mortality following emergency weekday admission was 6.53% compared to 7.06% following weekend admission. After case-mix adjustment, weekend admissions were associated with an increased risk of death, especially in the elective setting (elective OR = 1.32, 95% CI 1.23- 1.41; vs emergency OR = 1.09, 95% CI 1.05-1.13).
In a 2016 Australian study (Singla et al.), of 7718 elective and non-elective patients, it was shown that unadjusted and adjusted odds of early surgical mortality was higher on the weekend, compared to weekdays (unadjusted and adjusted OR = 1.30 (p<0.001) and 1.19 (p=0.026), respectively). When separated by day of week, there was a trend for higher surgical mortality on Friday, Saturday and Sunday vs all other days, although this did not reach statistical significance.
In the US, also in 2016, Glance et al. conducted a study of 305,853 elective and non-elective surgical patients; undergoing isolated coronary artery bypass graft surgery, colorectal surgery, open repair of abdominal aortic aneurysm, endovascular repair of abdominal aortic aneurysm, and lower extremity revascularisation. After controlling for patient risk and surgery type, weekend elective surgery (OR = 3.18; 95% CI 2.26-4.49; p<0.001) and weekend urgent surgery (OR = 2.11; 95% CI 1.68-2.66; p<0.001) were associated with a higher risk of death compared with weekday surgery. Weekend elective (OR = 1.58; 95% CI 1.29-1.93; p<0.001) and weekend urgent surgery (OR = 1.61; 95% CI 1.42-1.82; p<0.001) were also associated with a higher risk of major complications compared with weekday surgery.
Emergency department (ED) patientsEdit
ED admissions have also been well studied. The first major study was published in 2001 by Bell et al. In this Canadian study, 3,789,917 ED admissions were analysed. Weekend admissions were associated with significantly higher in-hospital mortality rates than weekday admissions among patients with ruptured abdominal aortic aneurysms (42% vs 36%, p<0.001), acute epiglottitis (1.7% vs 0.3%, p=0.04), and pulmonary embolism (13% vs 11%, p=0.009).
In another Canadian study (Cram et al., 2004), 641,860 admissions from the ED were investigated. The adjusted odds of death for patients admitted on weekends when compared with weekdays was 1.03 (95% CI 1.01-1.06; p=0.005). The weekend effect was larger in major teaching hospitals compared with non-teaching hospitals (OR = 1.13 vs 1.03, p=0.03) and minor teaching hospitals (OR = 1.05, p=0.11).
In a UK study in 2010, Aylin et al. studied 4,317,866 ED admissions, and found 215,054 in-hospital deaths with an overall crude mortality rate of 5.0% (5.2% for all weekend admissions and 4.9% for all weekday admissions). The overall adjusted odds of death for all emergency admissions was 10% higher (OR = 1.10; 95% CI 1.08-1.11) in those patients admitted at the weekend compared with patients admitted during a weekday (p<0.001).
Handel et al., in 2012, carried out a similar study in the UK (Scotland) on 5,271,327 ED admissions. There was a significantly increased probability of death associated with a weekend emergency admission compared with admission on a weekday (OR = 1.27; 95% CI 1.26-1.28, p<0.0001). However, in 2013, Powell et al., in the US, analysed 114,611 ED admissions with a principal diagnosis consistent with sepsis, and found that the difference for overall inpatient mortality (in terms of the weekend) was not significant (17.9% vs 17.5%, p=0.08).
In 2016, Shin et al., in Taiwan, studied 398,043 patients with severe sepsis. Compared with patients admitted on weekends, patients admitted on weekdays had a lower 7-day mortality rate (OR = 0.89, 95% CI 0.87-0.91), 14-day mortality rate (OR = 0.92, 95% CI 0.90-0.93), and 28-day mortality rate (OR = 0.97, 95% CI 0.95-0.98).
Also in the US, in 2013, Sharp et al. studied 4,225,973 adult ED admissions. They found that patients admitted on the weekend were significantly more likely to die than those admitted on weekdays (OR = 1.073; 95% CI 1.06-1.08). However, Smith et al. (2014) in a smaller study (of 20,072 patients) in the US, found that weekend mortality was not significantly higher at 7 days (OR = 1.10; 95% CI 0.92-1.31; p=0.312) or at 30 days (OR = 1.07; 95% CI 0.94-1.21; p=0.322). By contrast, they found adjusted public holiday mortality in the all public holidays was 48% higher at 7 days (OR = 1.48; 95% CI 1.12-1.95; p=0.006) and 27% higher at 30 days (OR = 1.27; 95% CI 1.02-1.57; p=0.031).
Also in 2014, in an Australian study, Concha et al. studied 3,381,962 ED admissions; and found that sixteen of 430 diagnosis groups had a significantly increased risk of death following weekend admission. They accounted for 40% of all deaths, and demonstrated different excess mortality risk patterns: early care effect (cardiac arrest); care effect washout (e.g., pulmonary embolism); patient effect (e.g., cancer admissions) and mixed (e.g., stroke). These findings are consistent with most of the disease-specific studies outlined below.
Blecker et al., in 2015, in the US, studied 57,163 ED admissions, before and after implementation of an intervention to improve patient care at weekends. The average length of stay decreased by 13% (95% CI 10-15%) and continued to decrease by 1% (95% CI 1-2%) per month as compared to the underlying time trend. The proportion of weekend discharges increased by 12% (95% CI 2-22%) at the time of the intervention and continued to increase by 2% (95% CI 1-3%) per month thereafter. However, the intervention had no impact on readmissions or mortality.
In a smaller Danish study (of 5,385 patients) in 2016, it was found that there was a higher mortality for patients attending the ED during the evening shift than during the dayshifts, and during weekends than during weekdays (Biering et al.). Patients attending the ED during the night shift had no excess mortality compared with the day shifts. The combination of evening shift and weekday and the combination of dayshift and weekend reached significance.
Not all ED studies show the weekend effect. Some argue that it relates to higher acuity patients being admitted over the weekend. For example, also in 2016, Mohammed et al. in the UK, studied 58,481 emergency adult medical admissions in three acute hospitals with the electronic National Early Warning Score (NEWS) recorded within 24 hours of admission. Admissions over the weekend had higher index NEWS (weekend: 2.24 vs weekday: 2.05; p<0.001) with a higher risk of death (weekend: 6.65% vs weekday: 5.49%; OR = 1.10, 95% CI 1.01-1.19, p=0.023) which was no longer seen after adjusting for the index NEWS (OR = 1.00, 95% CI 0.92-1.08, p=0.94).
Intensive care unit patientsEdit
As well as ED, ICU care has been extensively studied in terms of weekend mortality. In 2002, Barnett et al. studied 156,136 patients in the US. They found the in-hospital death was 9% higher (OR = 1.09; 95% CI 1.04-1.15; p<0.001) for weekend admissions (Saturday or Sunday) than in patients admitted midweek (Tuesday to Thursday). However, the adjusted odds of death were also higher (p<0.001) for patients admitted on a Monday (OR = 1.09) or a Friday (OR = 1.08). Findings were generally similar in analyses stratified by admission type (medical vs. surgical), hospital teaching status, and illness severity.
In 2003, in Finland, Uusaro et al., studied 23,134 consecutive ICU patients. Adjusted ICU-mortality was higher for weekend as compared with weekday admissions (OR = 1.20; 95% CI 1.01-1.43).
But not all ICU studies show an effect. For example, in the following year, Ensminger et al.(2004) published a similar study in the US, looking at a significantly smaller population (of 29,084 patients). In multivariable analyses - controlling for the factors associated with mortality such as APACHE (acute physiology and chronic health evaluation) III predicted mortality rate, ICU admission source, and intensity of treatment - no statistically significant difference in hospital mortality was found between weekend and weekday admissions in the study population (OR = 1.06; 95% CI 0.95-1.17)
A small study in Saudi Arabia was published by Arabi et al. in 2006. A total of 2,093 admissions were included in the study. Again, there was no significant difference in hospital mortality rate between weekends and weekdays. Similarly, Laupland et al., in 2008, in Canada studied 20,466 ICU admissions. After controlling for confounding variables using logistic regression analyses, neither weekend admission nor discharge was associated with death. However, both night admission and discharge were independently associated with mortality.
However, in 2011, Bhonagiri et al., in a huge study of 245,057 admissions in 41 Australian ICUs, found that weekend admissions had a 20% hospital mortality rate compared with 14% on weekdays (p<0.001), with SMRs of 0.95 (95% CI 0.94-0.97) and 0.92 (95% CI 0.92-0.93). Conversely, Ju et al., in China, in 2013 studied 2,891 consecutive ICU patients; and found no mortality difference between weekend and workday admissions (p= 0.849).
In a French study in 2015, 5,718 ICU inpatient stays were included (Neuraz et al.).The risk of death increased by 3.5 (95% CI 1.3-9.1) when the patient-to-nurse ratio was greater than 2.5, and by 2.0 (95% CI 1.3-3.2) when the patient-to-physician ratio exceeded 14. The highest ratios occurred more frequently during the weekend for nurse staffing and during the night for physicians (p<0.001).
In another small French study (in 2016), Brunot et al., investigated 2428 patients. They found that weeknight and weekend (off-hour admissions), did not influence the prognosis of ICU patients. However, they did conclude that the higher illness severity of patients admitted during the second part of the night (00:00-07:59) may explain the observed increased mortality of that time period.
Also in 2016, Arulkamaran et al., in the UK, studied 195,428 ICU patients. After adjustment for casemix, there was no difference between weekends and weekdays (P=0.87) or between night-time and daytime (P=0.21).
Two studies into paediatric ICUs have been carried out. In 2005, Hixson et al., in a US study of 5968 patients admitted to paediatric ICU, found neither weekend admission (p=0.15), weekend discharge/death (p=0.35), nor evening PICU admission (p=0.71) showed a significant relationship with mortality. Fendler et al., in 2012, in a study of 2240 Polish paediatric ICU patients, found mortality was 10.9% and did not differ depending on weekend or weekday admission (10.95% vs 10.86% respectively, p=0.96).
Other non-selected patientsEdit
Schilling et al., in 2010, investigated 166,920 patients admitted to 39 Michigan hospitals. Participants were adults, 65 years+, and admitted through the emergency department with six common discharge diagnoses (acute myocardial infarction, congestive heart failure, stroke, pneumonia, hip fracture, gastrointestinal bleeding). Seasonal influenza conferred the greatest increase in absolute risk of in-hospital mortality (0.5%; 95% CI 0.23-0.76), followed by weekend admission (0.32%; 95% CI 0.11-0.54), and high hospital occupancy on admission (0.25; 95% CI 0.06-0.43).
In a huge study in 2012 by Freemantle et al., 14,217,640 admissions (all types) were assessed. Admission on weekend days was associated with an increase in risk of subsequent death compared with admission on weekdays. Hazard ratio for Sunday vs Wednesday 1.16 (95% CI 1.14-1.18; p<0.0001), and for Saturday vs Wednesday 1.11 (95% CI 1.09-1.13; p<.0001). Also in 2012, Lee et al., in Malaysia, studied 126,627 patients admitted to a single hospital. The group found that there was a statistically significant increased risk of mortality for those patients admitted during weekends (OR = 1.22; 95% CI 1.14-1.31) and out-of-hours on a weekday (OR = 1.67; 95% CI 1.57-1.78). As well as the effect of the weekend, there is a considerable literature on the effect of being admitted 'out-of-hours'. This effect is seen during the week and at weekends. This study by Lee is such a paper. The degree of effect is usually higher for the 'Out-of-Hours Effect' rather than the 'Weekend Effect'. This suggests that the 'weekend effect' may be nothing to do with the weekend per se, but may be caused by varying staff levels, and less intensive working practices, outside the '9-5 window'.
Ruiz et al., in 2015, researched 28 hospitals in England, Australia, US and the Netherlands; including both emergency and surgical-elective patients. This was an important study as it compared different healthcare systems throughout the developed world. They examined 2,982,570 hospital records. Adjusted odds of 30-day death were higher for weekend emergency admissions to 11 hospitals in England (OR = 1.08; 95% CI 1.04-1.13 on Sunday), 5 hospitals in US (OR = 1.13, 95% CI 1.04-1.24 on Sunday) and 6 hospitals in the Netherlands (OR = 1.20; 95% CI 1.09-1.33). Emergency admissions to the six Australian hospitals showed no daily variation in adjusted 30-day mortality, but showed a weekend effect at 7 days post emergency admission (OR = 1.12; 95% CI 1.04-1.22 on Saturday). All weekend elective patients showed higher adjusted odds of 30-day postoperative death; observing a 'Friday effect' for elective patients in the six Dutch hospitals. It seems that the ‘weekend effect’ is a phenomenon seen around the developed world.
Conway et al., in a 2016 Irish study of 30,794 weekend admissions (in 16,665 patients) found that the admission rate was substantially higher for more deprived areas, 12.7 per 1000 (95% CI 9.4-14.7) vs 4.6 per 1000 (95% CI 3.3-5.8).
Also in 2016, in the UK, Aldridge et al. surveyed 34,350 clinicians. They found substantially fewer specialists were present providing care to emergency admissions on Sunday (1667, 11%) than on Wednesday (6105, 42%). The Sunday-to-Wednesday intensity ratio was less than 0.7 in 104 (90%) of the contributing trusts. Mortality risk among patients admitted at weekends was higher than among those admitted on weekdays (OR = 1.10; 95% CI 1.08-1.11; p<0.0001). There was no significant association between Sunday-to-Wednesday specialist intensity ratios and weekend to weekday mortality ratios (r = -0.042; p=0.654).
Cardiac arrest In 2008, in the US, Pederby et al. investigated 58,593 cases of in-hospital cardiac arrest. Among in-hospital cardiac arrests occurring during day/evening hours, survival was higher on weekdays (20.6%; 95% CI 20.3%-21%) than on weekends (17.4%; 95% CI 16.8%-18%); odds ratio was 1.15 (95% CI 1.09-1.22). Day of week was not the only determinant of survival. Rates of survival to discharge was substantially lower during the night compared with day/evening; 14.7% (95% CI 14.3%-15.1%) vs 19.8% (95% CI 19.5%-20.1%). The authors concluded "survival rates from in-hospital cardiac arrest are lower during nights and weekends, even when adjusted for potentially confounding patient, event, and hospital characteristics".
In Japan, in 2011, Kioke et al., studied 173,137 cases of out-of-hospital cardiac arrest (OHCA). No significant differences were found between weekday and weekend/holiday cases, with odds ratios of 1.00 (95% CI 0.96-1.04; p=0.96) for 1-month survival and 0.99 (95% CI 0.94-1.04; p=0.78) for neurologically favourable 1-month survival.
In a study in 2015, Robinson et al., in the UK, analysed 27,700 patients who had had a cardiac arrest, in 146 UK acute hospitals. Risk-adjusted mortality was worse (p<0.001) for both weekend daytime (OR = 0.72; 95% CI 0.64-80), and night-time (OR = 0.58; 95 CI 0.54-0.63) compared with weekday daytime. In a much smaller study, also in 2015, Lee et al. studied 200 patients in South Korea. Rates of survival to discharge were higher with weekday care than with weekend care (35.8% vs 21.5%, p=0.041). Furthermore, complication rates were higher on the weekend than on the weekday, including cannulation site bleeding (3.0% vs 10.8%, p = 0.041), limb ischaemia (5.9% vs 15.6%, p = 0.026), and procedure-related infections (0.7% vs 9.2%, p = 0.005).
Psychiatry Patients Orellana et al., in Brazil, in 2013, investigated suicide amongst indigenous peoples of the state of Amazonas. They observed that most of the suicides has occurred among men, aged between 15 – 24 years, at home and during the weekend.
In a psychiatry study in the UK, in 2016, Patel et al. studied 7303 weekend admissions. Patients admitted at the weekend were more likely to present via acute hospital services, other psychiatric hospitals and the criminal justice system than to be admitted directly from their own home. Weekend admission was associated with a shorter duration of admission (B-coefficient -21.1 days, 95% CI -24.6-717.6, p<0.001) and an increased risk of readmission in the 12 months following index admission (incidence rate ratio 1.13, 95% CI 1.08-1.18, p<0.001); but in-patient mortality (OR = 0.79; 95% CI 0.51-0.23; p= 0.30) was not greater than for weekday admission.
Other studies In a palliative care study in Germany, Voltz et al. (2015) studied 2565 admitted patients - 1325 deaths were recorded. Of the deaths, 448 (33.8%) occurred on weekends and public holidays. The mortality rate on weekends and public holidays was 18% higher than that on working days (OR = 1.18; 95% CI 1.05-1.32; p=0.005). They concluded "Patients in the palliative care unit were at higher risk of dying on weekends and public holidays. In the absence of a prospective study, the exact reasons for this correlation are unclear." So, even in a situation where all the patients studied are dying, there is a weekend death effect, perhaps relating to differing work patterns.
In summary, there is strong evidence of a weekend effect when large non-disease specific groups of unselected patients are studied; both medical, surgical (both elective and non-elective patients) and ED. Patients who have had a cardiac arrest, or are palliative, also show the effect. There is variable evidence of an effect in ICU patients, adult and paediatric; also with variable evidence in psychiatry admissions.
Published research: Disease-specific (selected) patients: Cardiorespiratory medicineEdit
AMI Multiple studies have been carried out into acute myocardial infarction (AMI). In the first study, in Japan in 2007, Matsui et al. studied 6084 patients. There were no differences between the weekday and weekend groups in terms of in-hospital, 30-day, and 1-year mortality rates.
However, also in 2007, in a much larger US study (of 231,164 AMI patients), Kostis et al. found that the difference in mortality at 30 days was significant even after adjustment for demographic characteristics, coexisting conditions, and site of infarction (OR = 1.048; 95% CI 1.02-1.08; p<0.001).
In 2008, Kruth et al. in Germany, analysed 11,516 patients with ST-elevation myocardial infarction (STEMI). On weekends the group found a significantly higher in-hospital mortality (11.1 vs 9.4%, p=0.01) and at night there was a trend to higher in-hospital mortality when compared with regular working hours (10.6 vs 9.4%, p=0.07).
In small Japanese study, two years later, 370 AMI patients were studied (Turin et al., 2009). Odds ratio was 1.18 (95% CI 0.7-1.9) but there was no significant difference between weekend and weekday patients. Similarly, also in 2010, in South Korea, in another large study (97,466 patients), Hong el al, found the 30-day fatality rate was insignificantly different after adjustment for medical or invasive management (OR = 1.05; 95% CI 0.99-1.11).
Similarly, in 2012, in a study of 4616 AMI patients in Middle Eastern Countries, Al-Lawati et al. found no significant differences in 1-month (OR = 0.88; 95% CI 0.68-1.14) and 1-year mortality (OR = 0.88; 95% CI 0.70-1.10), respectively, between weekday and weekend admissions.
In the following year, 2013, five studies were published; three showed a weekend effect, two (smaller studies) did not. In Denmark, Hansen et al. studied 92,164 AMI patients. Mortality rates were higher on weekends within seven days of admission in 1997-99 (absolute difference ranging from 0.8 to 1.1%), with weekend-weekday hazard-ratios of 1.13 (95% CI 1.03-1.23) at day 2 and 1.10 (95% CI 1.01-1.18) at day 7. But there were no significant differences in 2000-09 and suggesting an attenuation of the initial 'weekend-effect', perhaps relating to more equitable care. Khera et al., in the US, carried out another huge study, of 1,434,579 patients with a STEMI. Weekend admission and multivessel PCI were independent predictors of in-hospital mortality among patients who underwent PCI for STEMI. Gyenes et al., in Canada, studied 6711 NSTEMI patients. Weekend admission was independently associated with higher mortality (OR = 1.52; 95% CI 1.15-2.01; p=0.004).
Rahthod et al., in the UK, studied 3347 STEMI patients, but did not find a weekend effect. In hospital mortality rates were comparable between the weekday and weekend groups (3.6% vs 3.2%) with day of presentation not predictive of outcome (OR = 1.25; 95% CI 0.74-2.11). In another small UK study in 2013, Showkathali et al., investigated 1471 STEMI patients and found a similar result. In-hospital mortality, 30-day mortality, and 1-year mortality were not different between weekday and weekend groups.
In 2014, in another Canadian study (of 11,981 AMI patients), O’Neill et al. found that, after adjusting for baseline risk factors, the hazards ratio for mortality was non-significant (OR = 1.06; 95% CI 0.82-1.38). Mortality at 1 year was also similar. Conversely, in the following year, in another Japanese study (of 111,200 patients, i.e. much larger than the previous two Japanese studies), Isogai et al., found in-hospital mortality was significantly higher for weekend admission, compared to weekday admission (13.6% vs 11.4%; p<0.001; OR = 1.22; 95% CI 1.17-1.27), despite the higher rate of PCI performed on the day of admission (68.9% vs 64.8%; p<0.001).
In South Korea in 2015, Kim et al., investigated 577 patients with NSTEMI or ACS. After adjustment for all confounding factors, weekend admission was associated with a 2.1-fold increased hazard for major adverse cardiac event (MACE), including cardiac death (OR = 2.13; 95% CI 1.26-3.60; p=0.005).
In 2016, in a huge American study by Khoshchehreh et al., of 13,988,772 patients with Acute Coronary Syndrome (ACS), adjusted mortality was higher for weekend admissions for Non-ST-Elevation Acute Coronary Syndromes (OR = 1.15, 95% CI 1.14-1.16); but only somewhat higher for ST-Elevation Myocardial Infarction (OR = 1.03; 95% CI 1.01-1.04). Additionally, patients were significantly less likely to receive coronary revascularisation intervention/therapy on their first day of admission; OR = 0.97 (95% CI 0.96-0.98) and OR = 0.75 (95% CI 0.75-0.75) for STEMI and NSTEMI respectively.
In another huge US study, also in 2016, 3,625,271 NSTEMI admissions were identified by Agrawal et al. Admission on a weekend vs weekday was independently associated with a lower rate of coronary angiography (OR = 0.88; 95% CI 0.89-0.90; p<0.001). And adjusted in-hospital mortality was significantly higher for the cohort of patients admitted on weekends (OR = 1.02; 95% CI 1.01-1.04; p<0.001).
PCI Noman et al., in the UK in 2012, studied 2571 consecutive PCI-treated STEMI patients. There was no difference in mortality between weekday and weekend groups (OR = 1.09, 95% CI 0.82-1.46; p=0.57). Similarly, no increase in mortality was seen in patients who underwent PCI at night (22:00-06:00).
Whereas, in 2015, Singh et al., in the US, carried out a much larger study of 401,571 PCI procedures. In a multivariate analysis, the weekend was a significant predictor of mortality.
Patel et al., in the USA in 2016, studied 4,376,950 patients who underwent PCI, focussing on a complication, upper GI bleed (UGIB). The incidence of UGIB was 1.1%. Mortality rate in the UGIB group was significantly higher (9.71% vs 1.1%, p <0.0001). They also found a higher risk of UGIB in urgent versus elective admissions, and weekend versus weekday admissions.
Other cardiac diseaseEdit
Three studies have been carried out into Acute Heart Failure (AHF). In 2009, in a US study of 48,612 patients with AHF, there were no differences in death rate by day of admission or discharge (Fornarow et al.). Conversely, in the same year, also in the US, Horwich et al. analysed 81,810 AHF admissions at 241 sites. Weekend AHF admission compared to weekday admission was associated with an increased in-hospital mortality (OR = 1.13; 95% CI 1.02-1.27). In a smaller Japanese study (of 1620 patients) in 2014, Hamaguchi et al., found in-hospital death was comparable between patients admitted on the weekend and weekdays (OR = 1.13; 95% CI 1.63-2.00; p=0.69).
Deshmukh et al., in the US in 2012, analysed 86,497 discharges with atrial fibrillation. The rate of AF requiring cardioversion was lower at the weekend when compared to a weekday (7.9% vs 16.2%, p<0.0001; OR = 0.5, 95% CI 0.45-0.55; p<0.0001). The adjusted hospital mortality odds was greater for weekend admissions (OR = 1.23, 95% CI 1.03-1.51; p<0.0001), after adjusting for patient and hospital characteristics and disease severity.
There have been three studies in cardiovascular surgery. In 2011, Kim et al. in the US, studied 97, 563 congenital heart surgery admissions to pediatric hospitals. Multivariable analysis demonstrated higher case complexity for weekend admission (OR = 2.6; p<0.001). No mortality data was presented.
Badheka et al., in the US, in 2014, studied 2127 patients who had had percutaneous aortic balloon valvotomy. Significant predictors of in-hospital mortality were the presence of increasing comorbidities (p=0.03), unstable patient (P<0.001), any complication (p<0.001), and weekend admission (p=0.008).
In 2016, in the US, Gonzalez et al. studied 176 paediatric patients placed on extracorporeal life support (ECLS). The most common indications for ECLS were congenital diaphragmatic hernia (33%) and persistent pulmonary hypertension (23%). When comparing 'in-hours' (40%) to 'out-off-hours' cannulation (60%), there were no significant differences in central nervous system complications, haemorrhage (extra-cranial), cannula repositioning, conversion from venovenous to venoarterial, mortality on ECLS, or survival-to-discharge.
In summary, in AMI and PCI (in the larger studies), and AF, there is good evidence of a weekend effect. AMI is a condition where a weekend effect might not have been predicted (i.e. a fairly random acute disease, traditionally looked after on a CCU where working patterns are usually similar through the week). In AHF, and Cardiothoracic Surgery, there is variable evidence of a weekend effect.
COPD There have been four studies in COPD (one including pneumonia), three on PE and two on pneumonia alone. In 2011, in a study of 9,915 admissions in the UK with an acute exacerbation of COPD, Brims et al. found that the adjusted odds ratio for death on day 1 after winter weekend admission was 2.89 (95% CI 1.04-8.08). But after opening a Medical Admission Unit, the OR for death day 1 after weekend winter admission fell from 3.63 (95% CI 1.15-11.5) to 1.65 (95% CI 0.14-19.01).
In the following year, in a much larger study (of 289,077 COPD patients), in Spain, Barba et al. discovered weekend admissions were associated with a significantly higher in-hospital mortality (12.9%) than weekday admissions (12.1%) (OR = 1.07; 95% CI 1.04-1.10). In 2014, in Canada, Suissa et al. published another very large study (of 323,895 patients) with COPD and pneumonia. They found mortality was higher for weekend (OR = 1.06; 95% CI 1.03-1.09) but not Friday admissions (OR = 0.97; 95% CI 0.95-1.00), relative to Monday-Thursday admissions.
In a US study of 25,301 COPD patients (Rinne et al., 2015), there were significantly fewer discharges on the weekend (1922 per weekend day vs 4279 per weekday, p<0.01); weekend discharges were significantly associated with lower odds of mortality within 30 days after discharge (OR = 0.80; 95% CI 0.65-0.99).
Pulmonary embolus Three first studies in Pulmonary Embolus (PE) have been carried out. The first was published by Aujesky in 2009, concerning 15,531 patients with PE in Switzerland. Patients admitted on weekends had a higher unadjusted 30-day mortality rate (11.1% vs 8.8%) than patients admitted on weekdays, with no difference in length of stay. Patients admitted on weekends had significantly greater adjusted odds of dying (OR = 1.17, 95% CI 1.03-1.34) than patients admitted on weekdays. Then Gallerani et al. in 2011, studied 26,560 Italian patients with PE. Weekend admissions were associated with significantly higher rates of in-hospital mortality than weekday admissions (28% vs. 24.8%) (p<0.001). The third study, by Nanchal et al. was carried out a year later, in the US, and was a huge one (of 1,143,707 patients). The authors found unadjusted mortality was higher for weekend admissions than weekday admissions (OR = 1.19; 95% CI 1.13-1.24). This increase in mortality remained statistically significant after controlling for potential confounding variables (OR = 1.17; 95% CI 1.11-1.22).
Pneumonia There are two studies concerning pneumonia. Firstly, in Taiwan, in 2012, Chang et al. described 788,011 patients. The patients admitted on weekends had a 3% higher odds of 30-day death compared with those admitted on weekdays (OR = 1.03; 95% CI 1.01-1.05). Secondly, in Japan, in 2016, Uematsu et al. studied 23,532 patients. After adjusting for baseline patient severity and need for urgent care, weekend admissions were associated with higher mortality (OR = 1.10; 95% CI 1.02-1.19).
In summary, there is good evidence of a weekend effect in a spectrum of respiratory disease, including COPD, PE and pneumonia.
Published research: Disease-specific (selected) patients: Gastroenterology, nephrology and other medical specialtiesEdit
Upper GI Bleed The studies related to Upper GI Bleed (UGIB) are almost as numerous as those on myocardial infarction; two focus on Acute Variceal Hemorrhage (AVH) alone. In 2009, in the US, Shaheen et al., found, in a study of 237,412 patients with UGI bleed, that those admitted on the weekend had an increased risk of death (3.4% vs 3.0%; OR = 1.08; 95% CI 1.02-1.15). In a similar US paper that year, Ananthakrishnan et al., studied another very large population (of 419,939 patients with UGIB). On multivariate analysis, non-variceal UGIB patients admitted on weekends had higher adjusted in-hospital mortality (OR = 1.21; 95% CI 1.09-1.35). Whereas, weekend admission was not predictive of in-hospital mortality in patients with AVH (OR = 0.94; 95% CI 0.75-1.18).
In another similar US study, by Dorn et al., in 2010, 98,975 patients with UGIB were studied, and a similar weekend effect found. Compared to patients admitted on a weekday, for those admitted on a weekend, in-hospital mortality was higher (unadjusted mortality 3.76 vs 3.33%; p = 0.003; adjusted OR = 1.09, 95% CI 1.00-1.18). Whereas, in a much smaller 2011 UK study (of 6749 patients), Jaraith et al., no weekend effect was found in UGIB. After adjustment for confounders, there was no evidence of a difference between weekend and weekday mortality (OR = 0.93; 95% CI 0.75-1.16).
Two further small studies were published in 2012. In South Korea, 388 UGIB (due to peptic ulcer) patients were studied by Youn et al. Most patients (97%) had undergone early endoscopy, but the mortality rate was not different between the two groups (1.8% overall vs 1.6% on the weekend). Whereas, in the Netherlands, de Groot et al., studied 571 patients with UGIB. The group found patients admitted during the weekend had a higher mortality rate than patients admitted during the week (9% vs 3%; OR = 2.68; 95% CI 1.07-6.72).
In 2014, Abougergi et al., in another very large US study (of 202,340 patients) found that (compared with patients admitted on weekdays), patients with non-variceal UGIB admitted on weekends had similar adjusted in-hospital mortality rates (OR = 1.11; 95% CI 0.93-1.30).
In a Scottish study of 60,643 patients with UGIB in 2015, there was no significant change in annual number of admissions over time; but there was a statistically significant reduction in 30-day case fatality from 10.3% to 8.8% (p<0.001) over 10 years (Ahmed et al.). Patients admitted with UGIB at weekends had a higher 30-day case fatality compared with those admitted on weekdays (p<0.001), after adjusting for comorbidities.
In 2016, Serrao et al., in the US, studied 85,971 patients with bleeding gastroduodenal angiodysplasia (GIAD). Mortality rates were higher for patients with weekend admission (2% vs 1%, p=0 .0002). And the adjusted odds ratio for inpatient mortality associated with weekend admission was elevated (OR = 2.4; 95% CI 1.5-3.9; p=0.0005)
Also in 2016, Weeda et al. in the USA, studied 119,353 patients in a metanalysis (of five studies, including their own. They found weekend admission for nonvariceal UGIB was associated with an increased odds of mortality (OR = 1.09; 95% CI 1.04-1.15).
UGIB (Variceal haemorrhage alone) In a Canadian study of 36,734 patients with AVH alone, Myers et al. (2009—after adjusting for confounding factors, including the timing of endoscopy - found that the risk of mortality was similar between weekend and weekday admissions (OR = 1.05; 95% CI 0.97-1.14). Similarly, in a much smaller South Korean study (of 294 AVH patients), Byun et al. (2012), found no weekend effect; when seventeen (23.0%) of 74 patients with a weekend admission and 48 (21.8%) of 220 with a weekday admission died during hospitalisation (p=0.872).
Other Gastroenterological Disease In 2016, in the US, Gaeteno et al. investigated 31,614 with cirrhosis and ascites. Among these admissions, approximately 51% (16,133) underwent paracentesis. Patients admitted on a weekend demonstrated less frequent use of early paracentesis (50% weekend vs 62% weekday) and increased mortality (OR = 1.12; 95% CI 1.01-1.25).
Two US studies of acute cholangitis were also published in 2016. Firstly, Inamdar et al. identified 23,661 patients who were admitted for cholangitis who required ERCP; of which 18,106 (76.5%) patients were admitted on the weekday, and 5,555 (23.5%) admitted on the weekend. By 24h, the weekday group had undergone ERCP more frequently than the weekend group (54.6 vs 43%; p<0.001). There was no statistical difference between the groups for in-hospital all-cause mortality (2.86 vs 2.56%; p=0.24), or length of stay (6.97 days vs 6.88 days; p=0.28). Secondly, in a much smaller study (of 181 patients), Tabibian et al. found no significant differences in mortality between weekend and weekday admission groups.
In a Japanese study, also in 2016, Hamada et al., studied 8328 patients hospitalised with severe acute pancreatitis. In-hospital mortality rates were not significantly different: 5.9% vs 5.4% for weekend and weekday admissions, respectively (OR = 1.06; 95% CI 0.83-1.35).
In summary, there is reasonable evidence (from larger studies) of a ‘weekend effect’ in UGIB (including bleeding gastroduodenal angiodysplasia) and paracentesis for cirrhosis and ascites; but little effect in AVH alone, and none in ERCP for cholangitis, or pancreatitis.
Nephrology and transplantationEdit
In a very large Canadian study (of 963,730) patients, in 2010, James et al., showed that (compared with admission on a weekday), AKI patients admitted on a weekend had a higher risk of death (OR = 1.07; 95% CI 1.02-1.12). Similarly, in a huge study of 3,278,572 American haemodialysis patients in 2013, Sakhuja et al., concluded that patients admitted over weekends had higher mortality during the first 3 days of admission (OR = 1.18; 95% CI 1.10-1.26).
Haddock et al., in the UK, in 2015, studied admissions to a renal unit. No weekend effect was observed. Thirty-day mortality rate was 46/208 = 0.22 deaths/weekend day of admission compared with 107/523 = 0.20 deaths/weekday of admission (OR = 1.08, p = 0.67). Acute kidney injury and haemodialysis patients formed a higher percentage of admissions.
Orman et al., in 2012, in the USA, studied 94,768 liver transplants. The patient survival rates did not significantly differ from those for daytime and weekday operations. The graft failure rate was unchanged at 30 and 90 days for weekend transplants but was modestly increased at 365 days (OR = 1.05; 95% CI 1.01-1.11).
In 2016, an American study of 181,799 deceased donor kidneys was carried out by Mohan et al. They found that organs procured on weekends, when compared with weekday kidneys, were significantly more likely to be discarded than transplanted (OR = 1.16; 95% CI 1.13–1.19). This was even after adjusting for organ quality (adjusted OR = 1.13; 95% CI 1.10–1.17). Of concern, was that the kidneys discarded at the weekend, were of a significantly higher quality than weekday discards (Kidney Donor Profile Index: 76.5% vs 77.3%).
In another study in 2016, Anderson et al., in the UK, studied 12,902 deceased-donor kidney alone transplants performed in 19 English transplant centres. In a Cox regression model, transplantation at the weekend was not associated with increased 1 year mortality, rehospitalisation or allograft failure/rejection.
In summary, in nephrology, and in aspects of renal and liver transplantation (not mortality), a weekend effect is (variably)seen. This is surprising as both renal and liver medicine usually do not vary clinical practice through the weekend.
Haematology-oncology and other medical specialtiesEdit
In a small study of 422 patients in 2010 with Acute Myeloid Leukaemia, also in the US, Bejanyan et al. did not see a difference in mortality based on day of admission. Similarly, in a much larger US study (of 12,043 patients with acute leukaemia), in 2014, Goodman et al. found that those admitted on the weekend did not have an increased mortality (OR = 1.0; 95% CI 0.8-1.6).
Conversely, in a large study (534,011) of US patients with metastatic carcinoma of the prostate also in 2014, Schimd et al. did show a weekend effect. In multivariate analysis, weekend admission was associated with an increased likelihood of complications (OR = 1.15, 95% CI 1.11-1.19) and mortality (OR = 1.20; 95% CI 1.14- 1.27).
Lapointe-Shaw et al., in Canada in 2016, studied 290,471 hospital admissions with cancer. Patients admitted to hospital on weekends/holidays had an increased 7-day in-hospital mortality (4.8% vs 4.3%; OR = 1.13; 95% CI 1.08-1.17); corresponding to 137 excess deaths per year compared with the weekday group. Among those who had procedures in the first 4 days of admission, fewer weekend/holiday-admitted patients had them performed in the first 2 days, for 8 of 9 common procedure groups.
In 2013, Wichmann et al. in a Danish study of 4762 episodes of opiate overdose, found age >50 years and overdose during the weekend significantly associated with 48h mortality.
In summary, in haematology and oncology, two out of three studies showed the weekend effect, both on >100,000 patients.
Published research: Disease-specific (selected) patients: neuroscienceEdit
Stroke With myocardial infarction and UGIB, the most well studied disease is stroke, with varying results regarding the weekend effect. Though there are three very large studies (>100,000 patients), two of which are positive.
In the first stroke study, by Saposnik et al. in 2007, 26,676 patients in 606 hospitals in Canada were assessed. Seven-day stroke mortality was 7.6%. Weekend admissions were associated with a higher stroke mortality than weekday admissions (8.5% vs 7.4%). In the multivariable analysis, weekend admissions were associated with higher early mortality (OR = 1.14; 95% CI 1.02-1.26) after adjusting for age, sex, comorbidities, and medical complications.
In Japan in the following year, a much smaller study of 1578 patients, was carried out by Turin et al. They found the 28-day case fatality rate for the weekend admission group was 14.7% (95% CI 11.3-18.8) and 10.1% (95% CI 8.5-11.9) for the weekday admission group. This phenomenon was observed mainly for cerebral infarction, and to some extent for cerebral haemorrhage. But it did not reach statistical significance. In 2009, Tung et al., in Taiwan, studied 34,347 ischaemic stroke patients and found that weekend admissions were associated with increased 30-day mortality.
Five studies were published in 2010; three showed a weekend effect. Kazley et al., in a US study of 78,657 patients, found no significant difference in mortality depending on day of admission. Similarly, in a larger US study (of 599,087 patients), Hoh et al., also found no difference in in-hospital mortality. Whereas Fang et al., in a Canadian study of 20,657 patients, reported that the all-cause 7-day fatality rate was higher in patients seen on weekends compared to weekdays (8.1% vs 7.0%), even after adjustment for age, sex, stroke severity, and comorbid conditions (OR = 1.12, 95% CI 1.00-1.25). Smith et al. carried out another (much larger) Canadian study with 1036 hospitals contributing 274,988 ischaemic stroke patients. Characteristics associated with in-hospital mortality were age, arrival mode (e.g., via ambulance vs other mode), history of atrial fibrillation, previous stroke, previous myocardial infarction, carotid stenosis, diabetes mellitus, peripheral vascular disease, hypertension, history of dyslipidemia, current smoking, and weekend or night admission. In the Netherlands, Ogbu et al., studied 82,219 ischaemic stroke admissions to 115 hospitals. A higher 7-day death risk for weekend admission, when compared to weekday admission, was seen (OR = 1.27; 95% CI 1.20-1.34).
In 2011, McKinney et al. in the US, studied a much larger number of patients (134,441). Ninety-day mortality was greater in patients with stroke admitted on weekends compared with weekdays (17.2% vs 16.5%; p=0.002). The adjusted risk of death at 90 days was significantly greater for weekend admission (OR = 1.05; 95% CI 1.02-1.09). In a much smaller US study, also in 2011, by O'Brien et al., 929 stroke patients were analysed. The overall risk of 28-day mortality was 9.6% for weekday strokes and 10.1% for weekend strokes. However, in a model controlling for patient demographics, risk factors, and event year, weekend arrival was not associated with 28-day mortality (OR = 0.87; 95% CI 0.51-1.50).
Three studies were published in 2012; two showed a weekend effect. Firstly, Palmer et al., in a study of 93,621 UK patients, found the rate of 7-day in-hospital mortality for Sunday admissions was 11.0% (OR = 1.26; 95% CI 1.16-1.37; with Monday used as a reference) compared with a mean of 8.9% for weekday admissions. Secondly, Albright et al., in a study of 8581 patients in the US, reported that weekend admission was not a significant independent predictor of in-hospital mortality (8.4 vs 9.9%, p=0.056), or 90-day mortality (18.2 vs 19.8%, p=0.680). Thirdly, in a Polish study, Niewada et al., studied 19,667 ischaemic stroke patients, in 72 stroke centres. More patients admitted on weekends died during hospitalisation or had poor outcome at discharge than weekday patients (15.9% and 59.8% vs. 14.1% and 55.3%, respectively).
In 2013 in France, Béjot et al., in a study of 5864 patients, found that onset during weekends/bank holidays was associated with a higher risk of 30-day mortality during 1985-2003 (OR = 1.26; 95% CI 1.06-1.51; p=0.01), but not during 2004-2010 (OR = 0.99; 95% CI 0.69-1.43; p=0.97). The authors concluded "The deleterious effect of weekends/bank holidays on early stroke mortality disappeared after the organization of a dedicated stroke care network in our community".
In 2014, Bray et al., in the UK, studied 56,666 patients in 103 stroke units. The authors found that the highest risk of death was observed in stroke services with the lowest nurse/bed ratios. In multivariable analysis, patients admitted on a weekend to a stroke unit with 1.5 nurses/ten beds had an estimated adjusted 30-d mortality risk of 15.2% (OR = 1.18, 95% CI 1.07-1.29) compared to 11.2% for patients admitted to a unit with 3.0 nurses/ten beds (OR = 0.85, 95% CI 0.77-0.93). The presence of specialist stroke physicians doing daily ward rounds did not have a significant effect on mortality.
Three studies in stroke were published in 2015, one which showed a weekend effect. In the largest study, 47,885 Japanese stroke patients were included (Inoue et al.). Of these patients, 32.0% were admitted to a Stroke ICU and 27.8% were admitted to a general medical ward (GMW) on a weekend. The estimated in-hospital mortality rate was significantly higher among the patients admitted to a GMW on a weekend compared with those admitted on a weekday (7.9% vs 7.0%), but this difference was not significant after adjusting for the patients' background characteristics. The estimated in-hospital mortality rates of the patients admitted to an S-ICU were similar between weekend and weekday admissions (10.0% vs 9.9%). In a UK stroke study of 37,888 patients, it was found that when compared with weekdays, mortality at seven days was increased significantly; by 19% for admissions on weekends—although the admission rate was 21% lower on weekends (Roberts et al.). Although not significant, there were indications of increased mortality at seven days for weekend admissions during winter months (31%), in the community (81%) rather than large hospitals (8%) and for patients resident furthest from hospital (32% for distances of >20 kilometres). In a much smaller Spanish study, 1250 patients were described; and no difference was found in in-hospital mortality (Romero Sevilla et al.). Regarding functional outcome at 3 months, 67.0% of weekday vs 60.7% of weekend admissions were independent (p=0.096); as were 65.5% of patients admitted during the academic months vs 3.5% of those admitted during summer holidays (p=0.803). They also identified a trend toward higher rates of thrombolysis administration on weekdays, during the morning shift, and during the academic months.
Four studies have, so far, been published in 2016; three showing a weekend effect, one not. Turner et al., in the UK, investigated 52,276 stroke events. OR for seven-day mortality, 30-day mortality and 30-day discharge for weekend admission compared to weekday was 1.17 (95% CI 1.05-1.30), 1.08 (95% CI 1.00 to 1.17) and 0.90 (95% CI 0.85 to 0.95), respectively. A smaller Korean study (of 8957 stroke patients) by Cho et al., also found evidence of an effect. After adjusting for patient and hospital characteristics, their frailty model analysis revealed significantly higher in-hospital mortality in patients admitted on weekends than in those admitted on weekdays (OR = 1.22; 95% CI 1.01-1.47).
Hsieh et al., in Taiwan, analysed 46,007 ischaemic stroke admissions. They found, in multivariate analysis without adjustment for stroke severity, weekend admission was associated with increased 30-day mortality (OR = 1.20; 95% CI 1.08-1.34). But this association did not persist after adjustment for stroke severity (OR = 1.07; 95% CI 0.95-1.20). Whereas, Ansa et al., in Nigeria in 2016, studied 339 patients, of which 187 (55.2%) had had a stroke. They found presentation to hospital after-hours was a significant predictor of death (OR = 3.37).
There has been one study of stroke in (8467) children, by Adil et al., in the US, in 2016. After adjusting for age, sex, and confounders, the odds of in-hospital mortality remained higher among children admitted on weekends (OR = 1.4; 95% CI 1.1-1.9; p=0.04).
Other neurological disease One study related to meningococcal septicaemia has been published. In 2013, Goldacre et al., in a UK study of 19,729 patients, found that the risk of in-hospital death was significantly higher (OR = 1.12; 95% CI 1.05-1.20) for weekend admission.
Intracranial haemorrhage Several studies have been published regarding intracranial bleeding: intracerebral, subarachnoid and subdural haemorrhage. In 2009 in the US, Crowley et al., in a study of 13,821 US patients with intracerebral haemorrhage (ICH), reported the risk of in-hospital death was 12% higher with weekend admission (OR = 1.12; 95% CI 1.05-1.20). In China, in 2012, Jiang et al., in a much smaller study (of 313 patients with ICH) found that weekend admission was not a statistically significant predictive factor of in-hospital mortality (p=0.315) or functional outcome (p=0.128). However, in 2016, Patel et al., also in the US, studied 485,329 patients with intracerebral haemorrhage (ICH). Overall, weekend admission was associated with 11% higher odds of in-hospital mortality. When analysed in 3-year groups, excess mortality of weekend admissions showed temporal decline.
Three relatively small studies on SAH have been carried out. Crowley et al., in the US in 2009, investigated patients with subarachnoid haemorrhage (SAH; 5667 patients). Unlike the group's other study, weekend admission was not a statistically significant independent predictor of death in the study population at 7 days (OR = 1.07, 95% CI 0.91-1.25), 14 days (OR = 1.01, 95% CI 0.87-1.17), or 30 days (OR = 1.03, 95% CI 0.89-1.19). In 2011, in China, Zhang et al., in a smaller study, analysed 183 patients with SAH. In logistic regression model, weekend admission was not an independent predictor of higher in-hospital mortality (OR = 1.77, 95% CI 0.83-3.77) after SAH. However a weekend effect was observed by Deshmukh et al., in 2016, when the group studied 385 UK patients with SAH. They found that the patients admitted on a weekend had a significantly higher scan to treatment time (83.1 ± 83.4 h vs 40.4 ± 53.4 h, p<0.0001) and admission to treatment (71.6 ± 79.8 h vs 27.5 ± 44.3 h, p < 0.0001) time. After adjustments for adjusted for relevant covariates, weekend admission was significantly associated with excess in-hospital mortality (OR = 2.1, 95% CI 1.13-4.0; p = 0.01).
In 2013, Busi et al., investigated 14,093 US patients with acute non-traumatic subdural haemorrhage. In multivariate analysis, weekend admission (OR = 1.19; 95% CI 1.02-1.38) was an independent predictor of in-hospital mortality.
Similarly, in 2017, Rumalia et al., in an American study of 404,212 patients with traumatic SDH, showed that weekend admission was associated with an increased likelihood of in-hospital complication (OR = 1.06-1.12), prolonged length of stay (OR = 1.08-1.17), and in-hospital mortality (OR: 1.04-1.11).
Other neurosurgical disease In 2012, in the US, Dasenbrook et al., studied 2714 patients with spinal metastases. Weekend admission was associated with a significantly lower adjusted odds of receiving surgery within 1 day (OR = 0.66; 95% CI 0.54-0.81; p<0.001) and within 2 days (OR = 0.68; 95% CI 0.56-0.83; p<0.001) of admission. But the adjusted odds of in-hospital death was not significantly different for those admitted on the weekend.
In 2012, Schneider et al., also in the US, carried out a study of 38,675 patients with traumatic brain injury. Weekend patients demonstrated 14% increased risk of mortality (OR = 1.14; 95% CI 1.05-1.23). However, Nandyala et al., in the following year, in a US study of 34,122 patients who had undergone cervical fusion for cervical spine trauma, found the mortality rate was not significantly different among the weekend patients.
Desai et al., in the US, in 2015, investigated 580 children undergoing emergency neurosurgical procedures. After multivariate analysis, children undergoing procedures during a weekday after hours or weekends were more likely to experience complications (p=0.0227), and had an increased mortality.
In 2016, Tanenbaum et al. in the US, studied 8,189 patients who had had atlantoaxial fusion. Significant predictors of in-hospital mortality included increased age, emergent or urgent admission, weekend admission, congestive heart failure, coagulopathy, depression, electrolyte disorder, metastatic cancer, neurologic disorder, paralysis, and non-bleeding peptic ulcer.
Atenello et al., in 2016, studied 99,472 US paediatric patients with shunted hydrocephalus, 16% of whom were admitted on a weekend. After adjustment for disease severity, time to procedure, and admission acuity, weekend admission was not associated with an increase in the inpatient mortality rate (p=0.46) or a change in the percentage of routine discharges (p=0.98) after ventricular shunt procedures. In addition, associations were unchanged after an evaluation of patients who underwent shunt revision surgery. High-volume centres were incidentally noted in multivariate analysis to have increased rates of routine discharge (OR = 1.04; 95% CI 1.01-1.07; p=0.02).
Also in 2016, Linzey et al., in the US, studied 15, 865 patients. This were all patients undergoing neurosurgery in a single centre (Michigan). Surgical morbidity was more common during weekend cases vs weekday cases (6.60% vs 4.65%, p=0.03). Surgical mortality during weekend cases was 0.87% compared to only 0.20% during weekdays (p<0.001).
In summary, in neuroscience, the evidence is less clear. In stroke, the weekend effect probably exists. Except for two studies (by Kazley et al., and Hoh et al., both in 2010), all the studies over 20,000 patients show the effect. In neurological/surgical conditions that may require surgery, there is variable evidence of a weekend effect.
Published research: Disease-specific (selected) patients: Paediatrics and obstetricsEdit
Neonatal mortality Several paediatric and obstetric studies have been performed. In fact, the first studies on the weekend effect were in this area in the late 1970s.
Possibly the first study of the weekend effect was a UK prospective study of 297,000 children, published in 1977, when childhood deaths were assessed. The paper stated "16 of the 29 sudden unexpected deaths occurred at a weekend or bank holiday".
In 1981, Hendry in the UK, stated that "babies born on Sundays were more at risk of dying during or after birth." Also in 1981, in the US, Mangold studied 66,049 live births. Neonatal mortality was found to be higher among weekend deliveries with a Sunday rate that was 27 per cent above the weekly average. Two years later, in Australia, Mathers concluded that "stillbirth and neonatal death rates were 17% and 29% higher respectively among babies born at weekends than among those born on weekdays".
In 2003, Hamilton et al., in an American study of 111,749 births, found that neonatal mortality was higher among the births on weekends than those during the week. However, in the same year, Gould et al. also in the US, studied 1,615,041 live births. Observed neonatal mortality increased was 2.80/1000 for weekday births and 3.12/1000 for weekend births (OR = 1.12; 95% CI 1.05-1.19; p=0.001). But after adjusting for birth weight, the increased odds of death for infants born on the weekend were no longer significant.
In 2004, Luo et al., studied 3,239,972 births recorded in Canada. The proportion of births on weekend days was 24% lower than the proportion on weekdays. Infants born on weekend days had slightly but significantly elevated risks of stillbirth (OR = 1.06, 95% CI 1.02-1.09) and early neonatal death (OR = 1.11, 95% CI 1.07-1.16). However, the higher risks disappeared after adjustment for gestational age.
Salihu et al., in another American study, in 2012, found that the neonatal mortality rate was higher on weekends (3.25/1000) compared to weekdays (2.87/1000)(p=0.042). In the same year, Ibrahimou et al., in a US study of twin births, found post-neonatal mortality risk was higher on weekends as compared to weekdays (OR = 1.19; 95% CI 1.04-1.36). Also twins born on weekends to teenage mothers (age<18) had a 35% greater risk for neonatal death (OR = 1.35; 95% CI 1.06-1.71.
In 2015, Palmer et al. in the UK carried out an observational study on outcomes from maternal and neonatal records; on 1,332,835 deliveries and 1,349,599 births. They found that performance across four of seven measures was significantly worse for women admitted, and babies born, at weekends. In particular, the perinatal mortality rate was 7.3 per 1000 babies delivered at weekends; 0.9 per 1000 higher than for weekdays (OR = 1.07; 95% CI 1.02-1.13). No consistent association between outcomes and staffing was identified, although trusts that complied with recommended levels of consultant presence had a perineal tear rate of 3.0% compared with 3.3% for non-compliant services (OR = 1.21; 95% CI 1.00-1.45.
The authors went on to make a prediction regarding the possible benefits of removing the ‘weekend effect’: "The results would suggest approximately 770 perinatal deaths and 470 maternal infections per year above what might be expected if performance was consistent across women admitted, and babies born, on different days of the week."
Other paediatric disease Mitchell et al., in New Zealand in 1988, carried out a small study of Sudden Infant Death Syndrome (SIDS). Examination of deaths by day of the week, and showed the weekend had more deaths than the weekdays (p=0.0002).
Goldstein et al., in 2014, studied 439,457 US paediatric patients who underwent a range of surgical procedures. After multivariate adjustment and regression, patients undergoing a weekend procedure were more likely to die (OR = 1.63; 95% CI 1.21-2.20).
Burstein et al., in a study of 71,180 South African paediatric trauma patients found that 8,815 (12.4%) resulted from Road Traffic Accidents. RTAs were more common on weekends than weekdays (2.98 vs 2.19 patients/day; p<0.001), representing a greater proportion of daily all-cause trauma (15.5% vs 11.2%; p<0.001). Moreover, weekend RTA patients sustained more severe injuries than on weekdays, and compared to weekend all-cause trauma patients (injury score 1.66 vs. 1.46 and 1.43; both p<0.001).
In obstetric and paediatrics, most studies did show a weekend effect. This is a concern as both specialties, traditionally, have similar work patterns throughout the week.
Published research: Disease-specific (selected) patients: Specialist surgeryEdit
The weekend effect have been assessed in a wide range of specific surgical conditions. Four studies were published in 2012. Worni et al., in the US, studied 151,774 patients who had had a laparoscopic appendectomy. Overall mortality (OR = 1.37; p=0.075) was not statistically different between weekday and weekend groups. Whereas the same group, found a weekend effect in a study of 31,832 patients who underwent urgent surgery for left-sided diverticulitis (Worni et al., 2012). In a risk-adjusted analysis, patients admitted on weekends had a significantly higher risk for any postoperative complication (OR = 1.10; p=0.005). A mortality analysis was not presented.
In the same year, in a small study of 404 US patients with small bowel obstruction, McVay et al., found that mortality was low at 1.7%, with no difference noted between the groups (p=0.35). This is not surprising with a small study of a lowish risk procedure. In the US, Orman et al., studied 94,768 liver transplant patients. Unadjusted Cox proportional hazards modelling showed that in comparison with weekday liver transplant patients, weekend liver transplant patients had an OR of 0.99 (95% CI 0.93-1.07) for mortality at 30 days (i.e. no weekend effect).
In 2017, Hoehn et al., in the USA, studied 50,707 patients who had undergone urgent colectomy. They found, on multivariate analysis, mortality was associated with patient age (10 years: OR = 1.31, p < 0.01), severity of illness (extreme: OR = 34.68, p < 0.01), insurance status (Medicaid: OR = 1.24, p < 0.01; uninsured: OR = 1.40, p < 0.01), and weekend admission (OR = 1.09, p = 0.04).
Trauma and orthopaedicsEdit
In 2011, Carr et al. carried out a study of 90,461 US patients with trauma. The authors found that patients presenting on weekends were less likely to die than patients presenting on weekdays (OR = 0.89; 95% CI 0.81-0.97). This is one of only two studies that have shown weekend mortality is less at the weekend.
There have been four studies looking at fracture of the neck of femur. In 2012, Daugaard et al., carried out a study on 38,020 Danish patients with a fractured neck of femur. The mortality rate for patients admitted during weekends or public holidays, or at night, was similar to that found for those admitted during working days. Whereas, two years later, Thomas et al., in a much smaller UK of 2989 consecutive patients, found that (whether managed surgically or conservatively), patients were more likely to die as an inpatient when admitted at the weekend (OR = 1.4, 95% CI 1.02-1.80; p=0.032).
However, in a US study of 344,989 patients with fractured neck of femur, in 2015, the opposite effect was found (Boylan et al.). Compared with patients admitted on weekdays, patients admitted on weekends had lower mortality (OR = 0.94; 95% CI 0.89-0.99) and shorter mean hospital stay (estimate, 3.74%; 95% CI 3.40-4.08); but did not differ in risk of perioperative complications (OR = 1.00; 95% CI 0.98-1.02). The authors concluded: "our study data do not support a weekend effect among hip fracture admissions in the United States". This is second study where a ‘weekday effect’ has been found.
In 2016, in Denmark, Kristiansen et al. investigated 25,305 patients undergoing hip fracture surgery. When comparing admission during weekends with admission during weekdays, off-hours admission was associated with a higher risk of surgical delay (OR = 1.19; 95% CI 1.05-1.37) and a higher 30-day mortality risk (OR = 1.13; 95% CI 1.04-1.23). They felt that "The risk of surgical delay appeared not to explain the excess 30-day mortality".
Three studies on major or polytrauma were carried out in 2016. Dei Giudici et al. carried out a small study (of 208 Italian polytrauma patients). No correlation between mortality and orthopaedic surgical timing was found.
Also in 2016, in the UK, Giannoudis et al. studied 1735 patients, and found mortality was lower in the weekend group: 39/360 pts (10.8%) compared to the weekday group: 100/670 pts (14.9%) but this did not reach statistical significance p=0.07). The relative risk (RR) of weekend mortality was 0.726 (95% CI: 0.513-1.027).
In another study on major trauma in 2016, in all 22 UK major trauma centres (MTC), Metcalfe et al., investigated 49,070 patients. Using multivariable logistic regression models, odds of secondary transfer into an MTC were higher at night (OR = 2.05, 95% CI 1.93-2.19) but not during the day at weekends (OR = 1.09; CI 0.99-1.19). Neither admission at night nor at the weekend was associated with increased length of stay, or higher odds of in-hospital death.
Two studies of ruptured abdominal aortic aneurysm (AAA) have been carried out. Both demonstrated the weekend effect. In 2012, Gellerani et al., in Italy, investigated 4461 patients. Weekend admissions were associated with significantly higher in-hospital mortality (43.4%) than weekday admissions (36.9%; p<0.001). Multivariate regression analysis showed that weekend admission was an independent risk factor for increased in-hospital mortality (OR = 1.32; 95% CI 1.14-1.52; p<0.001). Two years later, in the US, in a study of 5832 patients, Groves et al. found that patients admitted on the weekend had a statistically significant increase in mortality compared with those admitted on the weekdays (OR = 1.32; 95% CI 1.13-1.55; p=0.0004).
There are also two studies on lower limb ischaemia, both performed in the US. In a study of 63,768 patients with an ischaemic lower limb in 2014, Orandi et al. found no statistically significant association between weekend admission and in-hospital mortality (OR = 1.15; 95% CI 1.06-1.25; p=0.10). Whereas, Arora et al., a year later, in a similar study, did show a weekend effect. They found through multivariate analysis, that weekend admission (OR = 1.53; 95% CI 1.26-1.86; p<0.001) was a significant predictor of inhospital mortality.
In 2015, Tadisina et al. carried out the only study so far published on plastic surgery, investigating 50,346 US patients who had body contouring procedures. The authors found mortality rates to be higher on weekend admissions (3.7%) vs weekdays (0.5%). This is very surprising as presumably these are low risk operations.
Other specialist surgeryEdit
The first ENT study was carried out in the UK in 2016 by Patel et al. The authors found that 2208 elective tonsillectomies were performed on a weekday and 141 on the weekend. Post-tonsillectomy haemorrhages occurred in 104 patients (4.7%) who underwent the procedure on a weekday and in 10 patients (7.1%) who had surgery at the weekend (p = 0.20), i.e. not significantly different.
Also in 2016, Sayari et al., in the US, carried out a small study of (861) patients with esophageal atresia and tracheoesophageal fistula (EA/TEF). The cohort survival was 96%. Complication rates were higher with EA/TEF repair on a weekend (OR: 2.2) compared to a weekday. However weekend vs weekday procedure had no significant effect on mortality.
Blackwell et al., in the US, also in 2016, studied 10,301 patients who were admitted urgently for nephrolithiasis with obstruction to the renal tract. Weekend day admission significantly influenced time to intervention, and decreased the likelihood of intervention by 26% (p<0.001).
In summary, across a range of surgical conditions, little pattern was obvious with some conditions showing a weekend effect (e.g. small bowel obstruction and AAA) but others not (appendicitis and diverticulitis). In fractured neck of femur, two studies showed a weekend effect, two did not.
Published research: SummaryEdit
In summary, in a majority (over 60%) of the over 190 studies described above, mortality is increased if the patient is admitted at the weekend. Of these, there are 56 very large studies (of over 100,000 patients). These have included 27.5 million (27514157) patients. Of these 56 studies, 29 concern patients in the USA, and 11 in the UK or England. 25 are non-disease specific, 31 disease specific. 49/56 (88%) show the weekend effect, 6 no effect, one (Boylan et al, on fracture neck of femur) shows a weekday effect. All of the UK-based >100,000 patient studies show the weekend effect.
22/56 of these >100,000 patient studies, were carried out on over 1 million patients. Of these, 20/22 (91%) show the weekend effect, and 2 no effect (both neonatal mortality). The median relative risk (RR) of these papers is 1.11 (range 0.94-3.18), i.e. patients admitted at weekends are, on average, 11% more likely to die than those admitted in the week. This data takes into account confounding variables, as all these papers use regression analysis.
The following table summarises the larger studies (>100,000 patients) on the Weekend Effect and mortality:
Summary: Weekend Effect and Mortality (Studies of >100,000 Patients)
|Author||Year||Country||Number Patients||Disease||Relative Risk||Weekend Effect|
|Ricciardi||2011||USA||29991621||Surgery (non-elective, NE)||1.1||Yes|
|McClean||2016||UK||105002||Surgery (non-elective)||Not stated||Yes|
|Aylin||2013||UK||4133346||Surgery (elective, E)||1.82||Yes|
|Mohammed||2012||UK||4640516||Surg (NE + E)||1.09 (NE) / 1.32 (E)||Yes|
|Glance||2016||USA||305853||Surg (NE + E)||2.11 (NE) / 3.18 (E)||Yes|
|Powell||2013||USA||114611||ED (sepsis)||Not stated||No|
|Freemantle||2012||UK||14217640||Other||1.11 (Sat) / 1.16 (Sun)||Yes|
|Lee||2012||Malaysia, Eng, Australia, USA||126627||Other||1.22||Yes|
|Koike||2011||Japan||173137||Cardiac Arrest (out-of-hospital)||1.0||No|
|Khoshchehreh||2016||USA||13988772||STEMI (S) / NSTEMI (NS)||1.05 (S) / 1.3 (NS)||Yes|
|Suissa||2014||Canada||323895||COPD / pneumonia||1.06||Yes|
|Shaheen||2009||USA||237412||Upper GI Bleed||1.06||Yes|
|Ananthakrishnan||2009||USA||419939||Upper GI Bleed||1.21||Yes|
|Abougergi||2014||USA||202340||Upper GI Bleed||1.11||No|
|Weeda||2016||USA||119353||Upper GI Bleed||1.09||Yes|
|Patel||2016||USA||4376950||Upper GI Bleed (post PCI)||Not stated||Yes|
|James||2010||USA||963730||Acute Kidney Injury||1.07||Yes|
|Newcastle||1977||UK||297000||Paediatric mortality||Not stated||Yes|
|Hamilton||2003||USA||111749||Neonatal mortality||Not stated||Yes|
|Boylan||2015||USA||344989||Fracture neck of femur||0.94||Weekday effect|
Published research: DiscussionEdit
This weekend effect is seen in non-selected (non disease-specific) studies, medical and surgical; for both non-elective and elective admissions, in most countries in the developed world. In fact, the strength of the effect is highest in elective surgical care; the highest relative risk being 3.18 in Glance et al in 2016, and 1.82 in Aylin et al, in 2013. However, it is not entirely valid to compare weekend vs weekday mortality in elective and non-elective surgical patients; as they may not be from the same patient groups - e.g. the elective patients may be older, with comorbidities, with degenerative or malignant disease (e.g. hip replacement or bowel carcinoma), and the non-elective younger with infection or inflammation (e.g. appendicitis).
In terms of the disease-specific studies, the larger studies showed good evidence for a weekend effect in myocardial infarction, cardiac arrest, AF, pulmonary embolus, COPD, pneumonia, upper GI bleed, stroke (probably), AAA; and in specialties including plastic surgery, and paediatrics and obstetrics (probably), including SIDS. There is variable evidence of an effect in ICU and psychiatry; and no evidence of an effect in disease group-specific studies in general, orthopaedic, vascular and other specialist surgery.
Public holidays, and 'Out-of-Hours' (weekday) admission and discharge, have also been studied. Public holidays may have a greater effect than the weekend. Sharp et al., in their 2013 paper, studied over 4.2 million adult ED admissions; and found the adjusted public holiday mortality was 48% higher at 7 days and 27% higher at 30 days. Laupland et al. in 2008 in Canada, studied 20,466 ICU admissions. Both night admission and discharge were independently associated with mortality. Similar findings regarding weekday out-of-hours care have been found by Freemantle et al. in 2012; and in cardiac arrest, by Pederby et al. in 2008 in the US, and by Robinson et al. in 2015 in the UK.
It has been suggested that most (but not all) of the contradictory studies are smaller, single hospital and statistically underpowered (Aylin, 2016); two very large neonatology studies (Gould et al., 2003; Luo et al, 2004) are the exceptions. There is no evidence of a weekend effect in terms of neonatal mortality. That excluded, in other words, a large study multicentre study may be necessary to show an effect; probably over 100,000 patients, as suggested above.
The consistency of the effect (most show an increase in mortality of 10-15%) is further evidence of biomedical meaning, as the studies have been carried all over the developed world. Furthermore, there is a tendency for the effect to be larger in the larger studies. That the trend is almost always suggestive of a raised mortality at weekends (even in studies where the effect did not reach statistical significance) further supports the hypothesis. In other words, the effect is almost always the 'right way around'. Though it cannot be ruled out that positive publication bias could be a factor in this observation. There are two studies—both orthopaedic—that show that weekday mortality is more than the weekend (Carr et al., 2011; Boylan et al, 2015).
There are many reasons to think this effect is real. Firstly, the effect is seen in such a wide range of patients, medical and surgical, unselected and selected. Secondly, the effect is very consistent in terms of the degree of difference (10–15%). Thirdly, the effect is seen in many developed countries on several continents, all of which have a ‘Saturday/Sunday weekend concept’.
Furthermore, to make this point, Ruiz et al., in 2015 stated in the discussion in their International comparative study: "Due to limitations of administrative datasets, we cannot determine the reasons for these findings; however, the international nature of our database suggests that this is a systematic phenomenon affecting healthcare providers across borders."
Fourthly, in conditions where by their acute nature (e.g. AMI, pulmonary embolus and child birth), they are likely to be admitted on the day and be no more common on weekdays or weekends, the effect is still seen. Such conditions are normally looked after by teams that work normal patterns at weekends. This may also imply that the effect is strong, a ‘whole system’ issue, and be difficult to overcome. This is a concern. It is not clear why stroke has a variable effect. Fifthly, and finally—and perhaps the strongest argument—it is unlikely that elective care patients would have been chosen for surgery at the weekend if they were high risk.
There are several alternative explanations for this effect, including the hypothesis that an increase in mortality is due to a different (frailer) demography of patients being admitted at the end of the week (e.g. Friday and Saturday). There are two counter-arguments to this idea. Firstly, if this was the case, it is unlikely that the effect would be seen in elective admissions. Secondly, in most of the papers described above, weekend vs weekday data has been studied by multivariate analysis (i.e. taking comorbidities into account).
Cause of weekend effectEdit
The cause of this effect is unclear. It could be a ‘purely medical problem’, i.e. the mortality is increased due to reduced medical staffing levels at the weekend. The cardiology, nephrology, paediatric and obstetric studies are against this argument; as these are all specialties where senior medical staff usually work normally at weekends. It could be due to a combination of medical, nursing and other health professional staff being less available at weekends. There is some evidence for the importance of nursing numbers, in terms of weekend mortality. In Neuraz et al's study in 2015, the patient-to-nurse ratio was more important that the ratio of patient-to-physician. Alternatively, the effect may not just be a health issue, i.e. it could be due to reduced health and social care availability (that the patient may be discharged into) at the weekend.
As described above in the Discussion, there is also considerable literature on the 'Out-of-Hours Effect'. This effect is seen during the week and at weekends. The study by Lee et al in 2012, looked at (and compared) the 'Out-of-Hours' and 'Weekend Effect' on the same dataset (of 126,627 patients). In this, and other such studies, the degree of effect is usually higher for the 'Out-of-Hours Effect' rather than the 'Weekend Effect'. This suggests that the 'Weekend Effect' may be nothing to do with the weekend per se, but may be an effect caused by varying staffing levels, and less intensive working practices, outside the '9-5 Monday-Friday window'. In the Lee paper, the relative risk of 'Out-of-Hours Effect' was 1.67, compared to 1.22 for the 'Weekend Effect'.
Another alternative is that it may not be a health (or social, or both) issue at all. It could be a manifestation of a societal problem—i.e., due to a combination of health-social care and other (as yet unidentified) aspects of society (financial, working patterns of relatives etc.)—or nothing to do with health-social care. Indeed, a 'weekend effect' has been observed in other (non-health) aspects of society. For example, in the financial world, a 'weekend effect' is well documented. It is the phenomenon in financial markets, in which stock returns on Mondays are often significantly lower than those of the immediately preceding Friday. One theory attributes it to the tendency for companies to release bad news on a Friday after the markets close; which depresses stock prices on the following Monday. This is analogous to the theory put forward by some health professionals that challenge the (health) weekend effect by saying it is due to the tendency of GPs and nursing homes etc. to admit their iller patients on a Friday—so they do not have a problem over the weekend.
The Japanese paper by Koike et al in 2011, is important in this debate. It is a large study (of 173,137 patients) who had had an 'out-of-hospital' cardiac arrest. And importantly, its negative, with a relative risk of 1.0 - i.e. no weekend effect was seen. If the weekend effect was a societal problem (it could be), this might be positive. This gives some weight to the argument that it relates to health (plus or minus social) care and is amenable to change if we can change the cause(s), e.g. working patterns.
Of course, the (health) weekend 'effect' is really an association. A variety of possible causes have been discussed above. A combination of such factors is likely. And the solution will vary according to the cause(s). A huge controlled trial would be necessary to prove causation and reversilibility. This is unlikely to happen; so a more pragmatic approach will be required. If the cause cannot be identified, it can only be assumed that all these factors will have to be addressed, if we want to decrease the weekend effect. In Nov 2014, the East Midlands Senate published an extensive report that described the services provided by a group of hospitals in the UK during the week and at weekends. This is a good summary of the size of the task that may be ahead for the NHS.
Weekend effect and working patternsEdit
A small number of studies have examined the evidence for an association between the weekend effect and patterns of health professional working; six studies have addressed medical staffing, two have addressed nursing issues, and two have addressed both.
In 2011, in a study of COPD patients in the UK, Brims et al. found that after opening a Medical Admission Unit, the risk of death on day 1 after weekend winter admission fell from 3.63 (95% CI 1.15-11.5) to 1.65 (95% CI 0.14-19.01). Similarly, Bell et al., in 2013, in the UK, found an 'all inclusive' pattern of consultant working, incorporating a minimum consultant presence of 4 hours per day, was associated with reduced excess weekend mortality. In the US, in 2014, Ricciardi et al., in another medical study, found that mortality following a weekend admission for patients admitted to a hospital with resident trainees, was significantly higher than hospitals with no resident trainees.
The effects of the introduction of a 7-day consultant service have been investigated in medical patients. In 2015, Leong et al., in an uncontrolled study of elderly medical patients in the UK, stated "introduction of seven-day consultant working was associated with a reduction in in-hospital mortality from 11.4% to 8.8%". They also found that weekend discharges increased from general medical wards but did not increase from elderly medicine wards.
Blecker et al., also in 2015, in the US, studied 57,163 ED admissions, before and after implementation of an intervention to improve patient care at weekends. The average length of stay decreased by 13%, and the number of weekend discharges increased by 12%. But the intervention had no impact on readmissions or mortality.
Aldridge et al., in the UK in 2016, found that there was no significant association between Sunday-to-Wednesday specialist intensity ratios and weekend-to-weekday mortality ratios.
Two stroke studies have looked at working patterns. In 2013 in France, Bejot el al. found that onset during weekends/public holidays was associated with a higher risk of 30-day mortality during 1985-2003 but not during 2004-2010; before and after the introduction of a dedicated stroke care network. In 2014, Bray et al., in the UK, found that the highest risk of death observed was in stroke services with the lowest nurse/bed ratios.
Similarly, Ambrosi et al., in 2016, found that elderly medical patients in Italy who were receiving less care by Registered Nurses (RNs) at weekends, were at increased risk of dying; while those receiving a higher skill-mix, thus indicating that more nursing care was offered by RNs instead of Nursing Auxiliaries, were at less risk of dying.
Neuraz et al., in a French adult ICU study in 2015, found the risk of death increased when the patient-to-nurse ratio was greater than 2.5, and when the patient-to-physician ratio exceeded 14. The highest ratios occurred more frequently during the weekend for nurse staffing, and during the night for physicians. Similarly, Ozdemir et al., in a UK ED study in 2016, found that the lowest mortality rates were observed in hospitals with higher levels of medical and nursing staffing; and a greater number of operating theatres and critical care beds relative to hospital size.
It has long been argued that the weekend effect may be due to a lower quality of clinical services at the weekend. Australian researchers Richardson et al., in 2014 were the first to observe and quantify junior doctor work practices at the weekend. The authors report that doctors were frequently interrupted, engaged in high levels of multitasking, and had very few breaks when compared to work practices during the week.
In summary, there is variable evidence that working patterns are a factor in the weekend effect; with nurse:patient ratio possibly being more important than physicians' pattern of working. It is unclear whether changing the patterns will reverse the effect.
In July 2015, UK Health Secretary, Jeremy Hunt, quoted a mortality increase of 15% around weekends. This is in keeping with the literature outlined above. This figure had been used the UK Department of Health to propose a "7-day NHS" involving increased staffing at weekend.
The weekend effect is an area of particular interest in the UK's National Health Service, and some have attributed it to fewer staff being available during the weekend period. The Royal College of Physicians in 2010 issued a position statement,
"Hospitals undertaking the admission of acutely ill medical patients should have a consultant physician on‐site for at least 12 hours per day, seven days per week, at times related to peak admission periods. The consultant should have no other duties scheduled during this period.
While much of the work of the consultant physician will be on the acute medical unit, provision should be made for a daily consultant visit to all medical wards. In many hospitals this will require input from more than one physician."
Currently emergency treatment, or acute care, is available at all major NHS hospitals at weekends. In most hospitals, sick patients receive care from consultants in 'acute' specialties, such as Accident and Emergency, General and Orthopaedic Surgery, Medicine, Anaesthetics, Intensive care, Paediatrics, Obstetrics, Pathology and Radiology. However, most patients are seen at time of diagnosis of an illness and treated, but are not routinely reviewed by any doctor at weekends. In November 2013, the Academy of Royal Medical Colleges set out to address this matter in a document entitled Seven Day Consultant Present Care - Implementation Considerations. Research identified that patients in hospitals fell into ten key specialties, and discussed the benefit and costs of daily consultant review.
Elective services, or routine care, is rarely carried out at weekends. The provision of seven day elective services has proved divisive between doctors. In 2013, the NHS England (NHSE) Medical Director Prof Sir Bruce Keogh wrote that there is a clinical and compassionate argument for patient convenience. Other doctors state that overall patients are unlikely to benefit, and that limited NHS budget and resources would be better invested in providing better emergency care to improve mortality.
In 2015, Health Secretary Jeremy Hunt quoted that the 'weekend effect' in the NHS equated to 11,000 excess deaths a year. Some are now reporting the Hunt Effect - that some patients, too scared to attend hospital at weekends because of the weekend effect, have become seriously ill or even died as a direct consequence of waiting until Monday before seeking medical advice. The authors state,
"To assume that [the 11,000 deaths] are avoidable would be rash and misleading."
The paper was criticised by some clinicians unhappy with the findings, and a comment by a Professor of Cardiovascular Epidemiology suggested that the report was data-driven rather than based on a hypothesis; in fact the 2015 paper was a development from previous work which analysed an earlier data set in 2012.
In response to the 'weekend effect' and the lack of seven day elective services, there have been proposals for major reform to contracts of NHS staff. Staff are in support of strengthening weekend services, but junior doctors have criticised these changes as they do not account for the 40% increase in workload. The UK's main doctors union, the British Medical Association, is still negotiating, as they would like assurances that new contracts will safeguard against long working hours, and are fair for female employees and those with families. Junior doctors (any doctor in consultant training) have protested across the country that the changes to their contracts are not safe and may harm patients.
In July 2015, some UK consultants challenged suggestions that the weekend effect is due (in part) to consultants who opt out of weekends a figure later shown after FOI request to be less than 0.5%. However, in a BBC FOI request (in March 2014), it was found that "Hospitals in England had an average of 86 consultants on a Wednesday, compared to just over eight in the afternoon at the weekend."
Research published in 2017 analysing outcomes in 79 NHS Trusts in England which had instituted 7-day changes based on the "NHS Services, Seven Days a Week" policy, showed that these changes did not result in improvements in mortality rates, admission rates, length of hospital stay nor A&E four-hour breaches overall.
- Schmulewitz L, Proudfoot A, Bell D (2005). "The impact of weekends on outcome for emergency patients". Clin Med (Lond). 5 (6): 621–5. doi:10.7861/clinmedicine.5-6-621. PMC 4953143. PMID 16411359.CS1 maint: multiple names: authors list (link)
- Clarke MS, Wills RA, Bowman RV, Zimmerman PV, Fong KM, Coory MD, Yang IA (2010). "Exploratory study of the 'weekend effect' for acute medical admissions to public hospitals in Queensland, Australia". Intern Med J. 40 (11): 777–83. doi:10.1111/j.1445-5994.2009.02067.x. PMID 19811554.CS1 maint: multiple names: authors list (link)
- Marco J, Barba R, Plaza S, Losa JE, Canora J, Zapatero A (2010). "Analysis of the mortality of patients admitted to internal medicine wards over the weekend". Am J Med Qual. 25 (4): 312–8. doi:10.1177/1062860610366031. PMID 20484660.CS1 maint: multiple names: authors list (link)
- Mikulich O, Callaly E, Bennett K, O'Riordan D, Silke B (2011). "The increased mortality associated with a weekend emergency admission is due to increased illness severity and altered case-mix". Acute Med. 10 (4): 182–7. PMID 22111090.CS1 maint: multiple names: authors list (link)
- Bell D, Lambourne A, Percival F, Laverty AA, Ward DK (2013). "Consultant input in acute medical admissions and patient outcomes in hospitals in England: a multivariate analysis". PLOS ONE. 8 (4): e61476. Bibcode:2013PLoSO...861476B. doi:10.1371/journal.pone.0061476. PMC 3629209. PMID 23613858.CS1 maint: multiple names: authors list (link)
- Ricciardi R, Nelson J, Roberts PL, Marcello PW, Read TE, Schoetz DJ (2014). "Is the presence of medical trainees associated with increased mortality with weekend admission?". BMC Med Educ. 14: 4. doi:10.1186/1472-6920-14-4. PMC 3926858. PMID 24397268.CS1 maint: multiple names: authors list (link)
- Vest-Hansen B, Riis AH, Sørensen HT, Christiansen CF (2015). "Out-of-hours and weekend admissions to Danish medical departments: admission rates and 30-day mortality for 20 common medical conditions". BMJ Open. 5 (3): e006731. doi:10.1136/bmjopen-2014-006731. PMC 4360838. PMID 25762233.CS1 maint: multiple names: authors list (link)
- Huang CC, Huang YT, Hsu NC, Chen JS, Yu CJ (2016). "Effect of Weekend Admissions on the Treatment Process and Outcomes of Internal Medicine Patients: A Nationwide Cross-Sectional Study". Medicine (Baltimore). 95 (6): e2643. doi:10.1097/MD.0000000000002643. PMC 4753883. PMID 26871788.CS1 maint: multiple names: authors list (link)
- Ambrosi E, De Togni S, Guarnier A, Barelli P, Zambiasi P, Allegrini E, Bazoli L, Casson P, Marin M, Padovan M, Picogna M, Taddia P, Salmaso D, Chiari P, Frison T, Marognolli O, Canzan F, Saiani L, Palese A (2016). "In-hospital elderly mortality and associated factors in 12 Italian acute medical units: findings from an exploratory longitudinal study". Aging Clin Exp Res. 29 (3): 517–527. doi:10.1007/s40520-016-0576-8. PMID 27155980.CS1 maint: multiple names: authors list (link)
- Conway R, Cournane S, Byrne D, O'Riordan D, Silke B (2017). "Survival analysis of weekend emergency medical admissions". QJM. 110 (5): 291–297. doi:10.1093/qjmed/hcw219. PMID 28069914.CS1 maint: multiple names: authors list (link)
- Leong KS, Titman A, Brown M, Powell R, Moore E, Bowen-Jones D (2015). "A retrospective study of seven-day consultant working: reductions in mortality and length of stay". J R Coll Physicians Edinb. 45 (4): 261–7. doi:10.4997/JRCPE.2015.402. PMID 27070886.CS1 maint: multiple names: authors list (link)
- Black, Nick (2016). "Higher Mortality in Weekend Admissions to the Hospital : True, False, or Uncertain?" (PDF). JAMA. Journal of the American Medical Association. 316 (24): 2593–2594. doi:10.1001/jama.2016.16410. PMID 28027376.
- Ricciardi R, Roberts PL, Read TE, Baxter NN, Marcello PW, Schoetz DJ (2011). "Mortality rate after nonelective hospital admission". Arch Surg. 146 (5): 545–51. doi:10.1001/archsurg.2011.106. PMID 21576609.CS1 maint: multiple names: authors list (link)
- Ricciardi R, Nelson J, Francone TD, Roberts PL, Read TE, Hall JF, Schoetz DJ, Marcello PW (2016). "Do patient safety indicators explain increased weekend mortality?". J Surg Res. 200 (1): 164–70. doi:10.1016/j.jss.2015.07.030. PMID 26265383.CS1 maint: multiple names: authors list (link)
- Ozdemir BA, Sinha S, Karthikesalingam A, Poloniecki JD, Pearse RM, Grocott MP, Thompson MM, Holt PJ (2016). "Mortality of emergency general surgical patients and associations with hospital structures and processes". Br J Anaesth. 116 (1): 54–62. doi:10.1093/bja/aev372. PMID 26675949.CS1 maint: multiple names: authors list (link)
- McLean RC, McCallum IJ, Dixon S, O'Loughlin P (2016). "A 15-year retrospective analysis of the epidemiology and outcomes for elderly emergency general surgical admissions in the North East of England: A case for multidisciplinary geriatric input". Int J Surg. 28: 13–21. doi:10.1016/j.ijsu.2016.02.044. PMID 26892599.CS1 maint: multiple names: authors list (link)
- Aylin P, Alexandrescu R, Jen MH, Mayer EK, Bottle A (2013). "Day of week of procedure and 30 day mortality for elective surgery: retrospective analysis of hospital episode statistics". BMJ. 346: f2424. doi:10.1136/bmj.f2424. PMC 3665889. PMID 23716356.CS1 maint: multiple names: authors list (link)
- McIsaac DI, Bryson GL, van Walraven C (2014). "Elective, major noncardiac surgery on the weekend: a population-based cohort study of 30-day mortality". Med Care. 52 (6): 557–64. doi:10.1097/MLR.0000000000000137. PMID 24783992.CS1 maint: multiple names: authors list (link)
- Mohammed MA, Sidhu KS, Rudge G, Stevens AJ (2012). "Weekend admission to hospital has a higher risk of death in the elective setting than in the emergency setting: a retrospective database study of national health service hospitals in England". BMC Health Serv Res. 12: 87. doi:10.1186/1472-6963-12-87. PMC 3341193. PMID 22471933.CS1 maint: multiple names: authors list (link)
- Singla AA, Guy GS, Field JB, Ma N, Babidge WJ, Maddern GJ (2016). "No weak days? Impact of day in the week on surgical mortality". ANZ J Surg. 86 (1–2): 15–20. doi:10.1111/ans.13315. PMID 26424504.CS1 maint: multiple names: authors list (link)
- Glance LG, Osler T, Li Y, Lustik SJ, Eaton MP, Dutton RP, Dick AW (2016). "Outcomes are Worse in US Patients Undergoing Surgery on Weekends Compared With Weekdays". Med Care. 54 (6): 608–15. doi:10.1097/MLR.0000000000000532. PMID 27111750.CS1 maint: multiple names: authors list (link)
- Bell CM, Redelmeier DA (2001). "Mortality among patients admitted to hospitals on weekends as compared with weekdays". N Engl J Med. 345 (9): 663–8. doi:10.1056/NEJMsa003376. PMID 11547721.
- Cram P, Hillis SL, Barnett M, Rosenthal GE (2004). "Effects of weekend admission and hospital teaching status on in-hospital mortality". Am J Med. 117 (3): 151–7. doi:10.1016/j.amjmed.2004.02.035. PMID 15276592.CS1 maint: multiple names: authors list (link)
- Aylin P, Yunus A, Bottle A, Majeed A, Bell D (2010). "Weekend mortality for emergency admissions. A large, multicentre study". Qual Saf Health Care. 19 (3): 213–7. doi:10.1136/qshc.2008.028639. PMID 20110288.CS1 maint: multiple names: authors list (link)
- Handel AE, Patel SV, Skingsley A, Bramley K, Sobieski R, Ramagopalan SV (2012). "Weekend admissions as an independent predictor of mortality: an analysis of Scottish hospital admissions". BMJ Open. 2 (6): e001789. doi:10.1136/bmjopen-2012-001789. PMC 3533021. PMID 23135542.CS1 maint: multiple names: authors list (link)
- Powell ES, Khare RK, Courtney DM, Feinglass J (2013). "The weekend effect for patients with sepsis presenting to the emergency department". J Emerg Med. 45 (5): 641–8. doi:10.1016/j.jemermed.2013.04.042. PMID 23993937.CS1 maint: multiple names: authors list (link)
- Shih YN, Chen YT, Shih CJ, Ou SM, Hsu YT, Chen RC, Aisiku IP, Seethala RR, Frendl G, Hou PC (2017). "Association of weekend effect with early mortality in severe sepsis patients over time". J Infect. 74 (4): 345–351. doi:10.1016/j.jinf.2016.12.009. PMID 28025161.CS1 maint: multiple names: authors list (link)
- Sharp AL, Choi H, Hayward RA (2013). "Don't get sick on the weekend: an evaluation of the weekend effect on mortality for patients visiting US EDs". Am J Emerg Med. 31 (5): 835–7. doi:10.1016/j.ajem.2013.01.006. PMID 23465873.CS1 maint: multiple names: authors list (link)
- Smith S, Allan A, Greenlaw N, Finlay S, Isles C (2014). "Emergency medical admissions, deaths at weekends and the public holiday effect. Cohort study". Emerg Med J. 31 (1): 30–4. doi:10.1136/emermed-2012-201881. PMID 23345314.CS1 maint: multiple names: authors list (link)
- Concha OP, Gallego B, Hillman K, Delaney GP, Coiera E (2013). "Do variations in hospital mortality patterns after weekend admission reflect reduced quality of care or different patient cohorts? A population-based study". BMJ Qual Saf. 23 (3): 215–22. doi:10.1136/bmjqs-2013-002218. PMC 3933164. PMID 24163392.CS1 maint: multiple names: authors list (link)
- Blecker S, Goldfeld K, Park H, Radford MJ, Munson S, Francois F, Austrian JS, Braithwaite RS, Hochman K, Donoghue R, Birnbaum BA, Gourevitch MN (2015). "Impact of an Intervention to Improve Weekend Hospital Care at an Academic Medical Center: An Observational Study". J Gen Intern Med. 30 (11): 1657–64. doi:10.1007/s11606-015-3330-6. PMC 4617935. PMID 25947881.CS1 maint: multiple names: authors list (link)
- Biering K, Nielsen RF, Pérez N (2016). "Admission-time-dependent variation in mortality in a Danish emergency department". Dan Med J. 63 (1): A5173. PMID 26726901.CS1 maint: multiple names: authors list (link)
- Mohammed MA, Faisal M, Richardson D, Howes R, Beaston K, Speed K, Wright J (2016). "Adjusting for illness severity shows there is no difference in patient mortality at weekends or weekdays for emergency medical admissions". QJM. 110 (7): e1–e8. doi:10.1093/qjmed/hcw104. PMID 27413051.CS1 maint: multiple names: authors list (link)
- Barnett MJ, Kaboli PJ, Sirio CA, Rosenthal GE (2002). "Day of the week of intensive care admission and patient outcomes: a multisite regional evaluation". Med Care. 40 (6): 530–9. doi:10.1097/00005650-200206000-00010. PMID 12021679.CS1 maint: multiple names: authors list (link)
- Uusaro A, Kari A, Ruokonen E (2003). "The effects of ICU admission and discharge times on mortality in Finland". Intensive Care Med. 29 (12): 2144–8. doi:10.1007/s00134-003-2035-1. PMID 14600808.CS1 maint: multiple names: authors list (link)
- Ensminger SA, Morales IJ, Peters SG, Keegan MT, Finkielman JD, Lymp JF, Afessa B (2004). "The hospital mortality of patients admitted to the ICU on weekends". Chest. 126 (4): 1292–8. doi:10.1378/chest.126.4.1292. PMID 15486395.CS1 maint: multiple names: authors list (link)
- Arabi Y, Alshimemeri A, Taher S (2006). "Weekend and weeknight admissions have the same outcome of weekday admissions to an intensive care unit with onsite intensivist coverage". Crit Care Med. 34 (3): 605–11. doi:10.1097/01.ccm.0000203947.60552.dd. PMID 16521254.CS1 maint: multiple names: authors list (link)
- Laupland KB, Shahpori R, Kirkpatrick AW, Stelfox HT (2008). "Hospital mortality among adults admitted to and discharged from intensive care on weekends and evenings". J Crit Care. 23 (3): 317–24. doi:10.1016/j.jcrc.2007.09.001. PMID 18725035.CS1 maint: multiple names: authors list (link)
- Bhonagiri D, Pilcher DV, Bailey MJ (2011). "Increased mortality associated with after-hours and weekend admission to the intensive care unit: a retrospective analysis". Med J Aust. 194 (6): 287–92. PMID 21426282.CS1 maint: multiple names: authors list (link)
- Ju MJ, Tu GW, Han Y, He HY, He YZ, Mao HL, Wu ZG, Yin YQ, Luo JF, Zhu DM, Luo Z, Xue ZG (2013). "Effect of admission time on mortality in an intensive care unit in Mainland China: a propensity score matching analysis". Crit Care. 17 (5): R230. doi:10.1186/cc13053. PMC 4055975. PMID 24112558.CS1 maint: multiple names: authors list (link)
- Neuraz A, Guérin C, Payet C, Polazzi S, Aubrun F, Dailler F, Lehot JJ, Piriou V, Neidecker J, Rimmelé T, Schott AM, Duclos A (2015). "Patient Mortality Is Associated With Staff Resources and Workload in the ICU: A Multicenter Observational Study". Crit Care Med. 43 (8): 1587–94. doi:10.1097/CCM.0000000000001015. PMID 25867907.CS1 maint: multiple names: authors list (link)
- Brunot V, Landreau L, Corne P, Platon L, Besnard N, Buzançais A, Daubin D, Serre JE, Molinari N, Klouche K (2016). "Mortality Associated with Night and Weekend Admissions to ICU with On-Site Intensivist Coverage: Results of a Nine-Year Cohort Study (2006-2014)". PLOS ONE. 11 (12): e0168548. Bibcode:2016PLoSO..1168548B. doi:10.1371/journal.pone.0168548. PMC 5199040. PMID 28033395.CS1 maint: multiple names: authors list (link)
- Arulkumaran N, Harrison DA, Brett SJ (2017). "Association between day and time of admission to critical care and acute hospital outcome for unplanned admissions to adult general critical care units: cohort study exploring the 'weekend effect'". Br J Anaesth. 118 (1): 112–122. doi:10.1093/bja/aew398. hdl:10044/1/41749. PMID 27927721.CS1 maint: multiple names: authors list (link)
- Hixson ED, Davis S, Morris S, Harrison AM (2005). "Do weekends or evenings matter in a pediatric intensive care unit?". Pediatr Crit Care Med. 6 (5): 523–30. doi:10.1097/01.pcc.0000165564.01639.cb. PMID 16148810.CS1 maint: multiple names: authors list (link)
- Fendler W, Klobusinska J, Walenciak Ł, Młynarski W, Piotrowski A (2012). "Weekend admissions to paediatric/neonatal intensive care units are associated with longer hospitalisation time but not with greater mortality". Anaesthesiol Intensive Ther. 44 (4): 204–7. PMID 23348487.CS1 maint: multiple names: authors list (link)
- Schilling PL, Campbell DA Jr, Englesbe MJ, Davis MM (2010). "A comparison of in-hospital mortality risk conferred by high hospital occupancy, differences in nurse staffing levels, weekend admission, and seasonal influenza". Med Care. 48 (3): 224–32. doi:10.1097/MLR.0b013e3181c162c0. PMID 20168260.CS1 maint: multiple names: authors list (link)
- Freemantle N, Richardson M, Wood J, Ray D, Khosla S, Shahian D, Roche WR, Stephens I, Keogh B, Pagano D (2012). "Weekend hospitalization and additional risk of death: an analysis of inpatient data". J R Soc Med. 105 (2): 74–84. doi:10.1258/jrsm.2012.120009. PMC 3284293. PMID 22307037.CS1 maint: multiple names: authors list (link)
- Lee KG, Indralingam V (2012). "A Study of Weekend and Off-hour Effect on Mortality in a Public Hospital in Malaysia". Med J Malaysia. 67 (5): 478–82. PMID 23770862.
- Ruiz M, Bottle A, Aylin PP (2015). "The Global Comparators project: international comparison of 30-day in-hospital mortality by day of the week". BMJ Qual Saf. 24 (8): 492–504. doi:10.1136/bmjqs-2014-003467. PMC 4515980. PMID 26150550.CS1 maint: multiple names: authors list (link)
- Conway R, Cournane S, Byrne D, O'Riordan D, Coveney S, Silke B. The Relationship Between Social Deprivation and a Weekend Emergency Medical Admission. Acute Med. 2016; 15(3): 124-129
- Aldridge C, Bion J, Boyal A, Chen YF, Clancy M, Evans T, Girling A, Lord J, Mannion R, Rees P, Roseveare C, Rudge G, Sun J, Tarrant C, Temple M, Watson S, Lilford R (2016). "Weekend specialist intensity and admission mortality in acute hospital trusts in England: a cross-sectional study". Lancet. 388 (10040): 178–86. doi:10.1016/S0140-6736(16)30442-1. PMC 4945602. PMID 27178476.CS1 maint: multiple names: authors list (link)
- Peberdy MA, Ornato JP, Larkin GL, Braithwaite RS, Kashner TM, Carey SM, Meaney PA, Cen L, Nadkarni VM, Praestgaard AH, Berg RA (2008). "Survival from in-hospital cardiac arrest during nights and weekends". JAMA. 299 (7): 785–92. doi:10.1001/jama.299.7.785. PMID 18285590.CS1 maint: multiple names: authors list (link)
- Koike S, Tanabe S, Ogawa T, Akahane M, Yasunaga H, Horiguchi H, Matsumoto S, Imamura T (2011). "Effect of time and day of admission on 1-month survival and neurologically favourable 1-month survival in out-of-hospital cardiopulmonary arrest patients". Resuscitation. 82 (7): 863–8. doi:10.1016/j.resuscitation.2011.02.007. PMID 21397380.CS1 maint: multiple names: authors list (link)
- Robinson EJ, Smith GB, Power GS, Harrison DA, Nolan J, Soar J, Spearpoint K, Gwinnutt C, Rowan KM (2015). "Risk-adjusted survival for adults following in-hospital cardiac arrest by day of week and time of day: observational cohort study". BMJ Qual Saf. 25 (11): 832–841. doi:10.1136/bmjqs-2015-004223. PMC 5136724. PMID 26658774.CS1 maint: multiple names: authors list (link)
- Lee DS, Chung CR, Jeon K, Park CM, Suh GY, Song YB, Hahn JY, Choi SH, Choi JH, Gwon HC, Yang JH (2016). "Survival After Extracorporeal Cardiopulmonary Resuscitation on Weekends in Comparison With Weekdays". Ann Thorac Surg. 101 (1): 133–40. doi:10.1016/j.athoracsur.2015.06.077. PMID 26431921.CS1 maint: multiple names: authors list (link)
- Orellana JD, Basta PC, de Souza ML (2013). "Mortality by suicide: a focus on municipalities with a high proportion of self-reported indigenous people in the state of Amazonas, Brazil". Rev Bras Epidemiol. 16 (3): 658–69. doi:10.1590/s1415-790x2013000300010. PMID 24896279.CS1 maint: multiple names: authors list (link)
- Patel R, Chesney E, Cullen AE, Tulloch AD, Broadbent M, Stewart R, McGuire P (2016). "Clinical outcomes and mortality associated with weekend admission to psychiatric hospital". Br J Psychiatry. 209 (1): 29–34. doi:10.1192/bjp.bp.115.180307. PMC 4929405. PMID 27103681.CS1 maint: multiple names: authors list (link)
- Voltz R, Kamps R, Greinwald R, Hellmich M, Hamacher S, Becker G, Kuhr K, Gaertner J (2014). "Silent night: retrospective database study assessing possibility of "weekend effect" in palliative care". BMJ. 349: g7370. doi:10.1136/bmj.g7370. PMC 4267701. PMID 25515670.CS1 maint: multiple names: authors list (link)
- Matsui K, Kojima S, Sakamoto T, Ishihara M, Kimura K, Miyazaki S, Yamagishi M, Tei C, Hiraoka H, Sonoda M, Tsuchihashi K, Ooie T, Honda T, Ogata Y, Ogawa H (2007). "Weekend onset of acute myocardial infarction does not have a negative impact on outcome in Japan". Circ J. 71 (12): 1841–4. doi:10.1253/circj.71.1841. PMID 18037733.CS1 maint: multiple names: authors list (link)
- Kostis WJ, Demissie K, Marcella SW, Shao YH, Wilson AC, Moreyra AE (2007). "Weekend versus weekday admission and mortality from myocardial infarction". N Engl J Med. 356 (11): 1099–109. doi:10.1056/NEJMoa063355. PMID 17360988.CS1 maint: multiple names: authors list (link)
- Krüth P, Zeymer U, Gitt A, Jünger C, Wienbergen H, Niedermeier F, Glunz HG, Senges J, Zahn R (2008). "Influence of presentation at the weekend on treatment and outcome in ST-elevation myocardial infarction in hospitals with catheterization laboratories". Clin Res Cardiol. 97 (10): 742–7. doi:10.1007/s00392-008-0671-8. PMID 18465106.CS1 maint: multiple names: authors list (link)
- Turin TC, Kita Y, Rumana N, Sugihara H, Morita Y, Tomioka N, Okayama A, Nakamura Y, Ueshima H (2009). "Incidence, admission and case-fatality of acute myocardial infarction: weekend versus weekday in a Japanese population: 16-year results from Takashima AMI Registry (1988-2003)". Eur J Epidemiol. 24 (2): 93–100. doi:10.1007/s10654-008-9308-5. PMID 19089589.CS1 maint: multiple names: authors list (link)
- Hong JS, Kang HC, Lee SH (2010). "Comparison of case fatality rates for acute myocardial infarction in weekday vs weekend admissions in South Korea". Circ J. 74 (3): 496–502. doi:10.1253/circj.cj-09-0678. PMID 20075558.CS1 maint: multiple names: authors list (link)
- Al-Lawati JA, Al-Zakwani I, Sulaiman K, Al-Habib K, Al Suwaidi J, Panduranga P, Alsheikh-Ali AA, Almahmeed W, Al Faleh H, Al Saif S, Hersi A, Asaad N, Al-Motarreb A, Mikhailidis DP, Amin H (2012). "Weekend versus weekday, morning versus evening admission in relationship to mortality in acute coronary syndrome patients in 6 middle eastern countries: results from gulf race 2 registry". Open Cardiovasc Med J. 6: 106–12. doi:10.2174/1874192401206010106. PMC 3447162. PMID 23002404.CS1 maint: multiple names: authors list (link)
- Hansen KW, Hvelplund A, Abildstrøm SZ, Prescott E, Madsen M, Madsen JK, Jensen JS, Sørensen R, Galatius S (2013). "Prognosis and treatment in patients admitted with acute myocardial infarction on weekends and weekdays from 1997 to 2009". Int J Cardiol. 168 (2): 1167–73. doi:10.1016/j.ijcard.2012.11.071. PMID 23199552.CS1 maint: multiple names: authors list (link)
- Khera S, Kolte D, Palaniswamy C, Mujib M, Aronow WS, Singh T, Gotsis W, Silverman G, Frishman WH (2013). "ST-elevation myocardial infarction in the elderly--temporal trends in incidence, utilization of percutaneous coronary intervention and outcomes in the United States". Int J Cardiol. 168 (4): 3683–90. doi:10.1016/j.ijcard.2013.06.021. PMID 23838593.CS1 maint: multiple names: authors list (link)
- Gyenes GT, Yan AT, Tan M, Welsh RC, Fox KA, Grondin FR, Deyoung JP, Rose BF, Gallo R, Kornder JM, Wong GC, Goodman SG (2013). "Use and timing of coronary angiography and associated in-hospital outcomes in Canadian non-ST-segment elevation myocardial infarction patients: insights from the Canadian Global Registry of Acute Coronary Events". Can J Cardiol. 29 (11): 1429–35. doi:10.1016/j.cjca.2013.04.035. PMID 23910228.CS1 maint: multiple names: authors list (link)
- Rathod KS, Jones DA, Gallagher SM, Bromage DI, Whitbread M, Archbold AR, Jain AK, Mathur A, Wragg A, Knight CJ (2013). "Out-of-hours primary percutaneous coronary intervention for ST-elevation myocardial infarction is not associated with excess mortality: a study of 3347 patients treated in an integrated cardiac network". BMJ Open. 3 (6): e003063. doi:10.1136/bmjopen-2013-003063. PMC 3696864. PMID 23811175.CS1 maint: multiple names: authors list (link)
- Showkathali R, Davies JR, Sayer JW, Kelly PA, Aggarwal RK, Clesham GJ (2013). "The advantages of a consultant led primary percutaneous coronary intervention service on patient outcome". QJM. 106 (11): 989–94. doi:10.1093/qjmed/hct132. PMID 23737507.CS1 maint: multiple names: authors list (link)
- O'Neill DE, Southern DA, O'Neill BJ, McMurtry MS, Graham MM (2014). "Weekend compared with weekday presentation does not affect outcomes of patients presenting with non-ST elevation acute coronary syndrome". Eur Heart J Acute Cardiovasc Care. 3 (2): 99–104. doi:10.1177/2048872613510086. PMID 24585942.CS1 maint: multiple names: authors list (link)
- Isogai T, Yasunaga H, Matsui H, Tanaka H, Ueda T, Horiguchi H, Fushimi K (2015). "Effect of weekend admission for acute myocardial infarction on in-hospital mortality: a retrospective cohort study". Int J Cardiol. 179: 315–20. doi:10.1016/j.ijcard.2014.11.070. PMID 25464474.CS1 maint: multiple names: authors list (link)
- Kim HJ, Kim KI, Cho YS, Kang J, Park JJ, Oh IY, Yoon CH, Suh JW, Youn TJ, Chae IH, Choi DJ (2015). "The effect of admission at weekends on clinical outcomes in patients with non-ST-segment elevation acute coronary syndrome and its contributing factors". J Korean Med Sci. 30 (4): 414–25. doi:10.3346/jkms.2015.30.4.414. PMC 4366962. PMID 25829809.CS1 maint: multiple names: authors list (link)
- Khoshchehreh M, Groves EM, Tehrani D, Amin A, Patel PM, Malik S (2016). "Changes in mortality on weekend versus weekday admissions for Acute Coronary Syndrome in the United States over the past decade". Int J Cardiol. 210: 164–72. doi:10.1016/j.ijcard.2016.02.087. PMC 4801736. PMID 26950171.CS1 maint: multiple names: authors list (link)
- Agrawal S, Garg L, Sharma A, Mohananey D, Bhatia N, Singh A, Shirani J, Dixon S (2016). "Comparison of Inhospital Mortality and Frequency of Coronary Angiography on Weekend Versus Weekday Admissions in Patients With Non-ST-Segment Elevation Acute Myocardial Infarction". Am J Cardiol. 118 (5): 632–4. doi:10.1016/j.amjcard.2016.06.022. PMID 27381668.CS1 maint: multiple names: authors list (link)
- Noman A, Ahmed JM, Spyridopoulos I, Bagnall A, Egred M (2012). "Mortality outcome of out-of-hours primary percutaneous coronary intervention in the current era". Eur Heart J. 33 (24): 3046–53. doi:10.1093/eurheartj/ehs261. PMID 22947609.CS1 maint: multiple names: authors list (link)
- Singh V, Badheka AO, Arora S, Panaich SS, Patel NJ, Patel N, Pant S, Thakkar B, Chothani A, Deshmukh A, Manvar S, Lahewala S, Patel J, Patel S, Jhamnani S, Bhinder J, Patel P, Savani GT, Patel A, Mohamad T, Gidwani UK, Brown M, Forrest JK, Cleman M, Schreiber T, Grines C (2015). "Comparison of inhospital mortality, length of hospitalization, costs, and vascular complications of percutaneous coronary interventions guided by ultrasound versus angiography". Am J Cardiol. 115 (10): 1357–66. doi:10.1016/j.amjcard.2015.02.037. PMID 25824542.CS1 maint: multiple names: authors list (link)
- Patel NJ, Pau D, Nalluri N, Bhatt P, Thakkar B, Kanotra R, Agnihotri K, Ainani N, Patel N, Patel N, Shah S, Kadavath S, Arora S, Sheikh A, Badheka AO, Lafferty J, Alfonso C, Cohen M. Temporal Trends, Predictors, and Outcomes of In-Hospital Gastrointestinal Bleeding Associated With Percutaneous Coronary Intervention. Am J Cardiol. 2016 Oct 15; 118(8): 1150-1157
- Fonarow GC, Abraham WT, Albert NM, Stough WG, Gheorghiade M, Greenberg BH, O'Connor CM, Nunez E, Yancy CW, Young JB (2008). "Day of admission and clinical outcomes for patients hospitalized for heart failure: findings from the Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients With Heart Failure (OPTIMIZE-HF)". Circ Heart Fail. 1 (1): 50–7. doi:10.1161/CIRCHEARTFAILURE.107.748376. PMID 19808270.CS1 maint: multiple names: authors list (link)
- Horwich TB, Hernandez AF, Liang L, Albert NM, Labresh KA, Yancy CW, Fonarow GC (2009). "Weekend hospital admission and discharge for heart failure: association with quality of care and clinical outcomes". Am Heart J. 158 (3): 451–8. doi:10.1016/j.ahj.2009.06.025. PMID 19699870.CS1 maint: multiple names: authors list (link)
- Hamaguchi S, Kinugawa S, Tsuchihashi-Makaya M, Goto D, Tsutsui H (2014). "Weekend versus weekday hospital admission and outcomes during hospitalization for patients due to worsening heart failure: a report from Japanese Cardiac Registry of Heart Failure in Cardiology (JCARE-CARD)". Heart Vessels. 29 (3): 328–35. doi:10.1007/s00380-013-0359-5. PMID 23653107.CS1 maint: multiple names: authors list (link)
- Deshmukh A, Pant S, Kumar G, Bursac Z, Paydak H, Mehta JL (2012). "Comparison of outcomes of weekend versus weekday admissions for atrial fibrillation". Am J Cardiol. 110 (2): 208–11. doi:10.1016/j.amjcard.2012.03.011. PMID 22481013.CS1 maint: multiple names: authors list (link)
- Kim YY, Gauvreau K, Bacha EA, Landzberg MJ, Benavidez OJ (2011). "Resource use among adult congenital heart surgery admissions in pediatric hospitals: risk factors for high resource utilization and association with inpatient death". Circ Cardiovasc Qual Outcomes. 4 (6): 634–9. doi:10.1161/CIRCOUTCOMES.111.963223. PMID 22010202.CS1 maint: multiple names: authors list (link)
- Badheka AO, Patel NJ, Singh V, Shah N, Chothani A, Mehta K, Deshmukh A, Ghatak A, Rathod A, Desai H, Savani GT, Grover P, Patel N, Arora S, Grines CL, Schreiber T, Makkar R, Rihal CS, Cohen MG, De Marchena E, O'Neill WW (2014). "Percutaneous aortic balloon valvotomy in the United States: a 13-year perspective". Am J Med. 127 (8): 744–753.e3. doi:10.1016/j.amjmed.2014.02.025. PMID 24608018.CS1 maint: multiple names: authors list (link)
- Gonzalez KW, Dalton BG, Weaver KL, Sherman AK, St Peter SD, Snyder CL (2016). "Effect of timing of cannulation on outcome for pediatric extracorporeal life support". Pediatr Surg Int. 32 (7): 665–9. doi:10.1007/s00383-016-3901-6. PMID 27220493.CS1 maint: multiple names: authors list (link)
- Brims FJ, Asiimwe A, Andrews NP, Prytherch D, Higgins BR, Kilburn S, Chauhan AJ (2011). "Weekend admission and mortality from acute exacerbations of chronic obstructive pulmonary disease in winter". Clin Med (Lond). 11 (4): 334–9. doi:10.7861/clinmedicine.11-4-334. PMC 5873741. PMID 21853828.CS1 maint: multiple names: authors list (link)
- Barba R, Zapatero A, Losa JE, Marco J, Plaza S, Rosado C, Canora J (2012). "The impact of weekends on outcome for acute exacerbations of COPD". Eur Respir J. 39 (1): 46–50. doi:10.1183/09031936.00013211. PMID 21659418.CS1 maint: multiple names: authors list (link)
- Suissa S, Dell'Aniello S, Suissa D, Ernst P (2014). "Friday and weekend hospital stays: effects on mortality". Eur Respir J. 44 (3): 627–33. doi:10.1183/09031936.00007714. PMID 24829270.CS1 maint: multiple names: authors list (link)
- Rinne ST, Wong ES, Hebert PL, Au DH, Lindenauer PK, Neely EL, Sulc CA, Liu CF (2015). "Weekend Discharges and Length of Stay Among Veterans Admitted for Chronic Obstructive Pulmonary Disease". Med Care. 53 (9): 753–7. doi:10.1097/MLR.0000000000000395. PMID 26147865.CS1 maint: multiple names: authors list (link)
- Aujesky D, Jiménez D, Mor MK, Geng M, Fine MJ, Ibrahim SA (2009). "Weekend versus weekday admission and mortality after acute pulmonary embolism". Circulation. 119 (7): 962–8. doi:10.1161/CIRCULATIONAHA.108.824292. PMC 2746886. PMID 19204300.CS1 maint: multiple names: authors list (link)
- Gallerani M, Imberti D, Ageno W, Dentali F, Manfredini R (2011). "Higher mortality rate in patients hospitalised for acute pulmonary embolism during weekends". Thromb Haemost. 106 (1): 83–9. doi:10.1160/TH11-02-0068. PMID 21544321.CS1 maint: multiple names: authors list (link)
- Nanchal R, Kumar G, Taneja A, Patel J, Deshmukh A, Tarima S, Jacobs ER, Whittle J (2012). "Pulmonary embolism: the weekend effect". Chest. 142 (3): 690–6. doi:10.1378/chest.11-2663. PMC 4694190. PMID 22459777.CS1 maint: multiple names: authors list (link)
- Chang GM, Tung YC (2011). "Factors associated with pneumonia outcomes: a nationwide population-based study over the 1997-2008 period". J Gen Intern Med. 27 (5): 527–33. doi:10.1007/s11606-011-1932-1. PMC 3326101. PMID 22095573.
- Uematsu H, Kunisawa S, Yamashita K, Fushimi K, Imanaka Y (2016). "Impact of weekend admission on in-hospital mortality in severe community-acquired pneumonia patients in Japan". Respirology. 21 (5): 905–10. doi:10.1111/resp.12788. hdl:2433/225513. PMID 27040008.CS1 maint: multiple names: authors list (link)
- Shaheen AA, Kaplan GG, Myers RP (2009). "Weekend versus weekday admission and mortality from gastrointestinal hemorrhage caused by peptic ulcer disease". Clin Gastroenterol Hepatol. 7 (3): 303–10. doi:10.1016/j.cgh.2008.08.033. PMID 18849015.CS1 maint: multiple names: authors list (link)
- Ananthakrishnan AN, McGinley EL, Saeian K (2009). "Outcomes of weekend admissions for upper gastrointestinal hemorrhage: a nationwide analysis". Clin Gastroenterol Hepatol. 7 (3): 296–302e1. doi:10.1016/j.cgh.2008.08.013. PMID 19084483.CS1 maint: multiple names: authors list (link)
- Dorn SD, Shah ND, Berg BP, Naessens JM (2010). "Effect of weekend hospital admission on gastrointestinal hemorrhage outcomes". Dig Dis Sci. 55 (6): 1658–66. doi:10.1007/s10620-009-0914-1. PMID 19672711.CS1 maint: multiple names: authors list (link)
- Jairath V, Kahan BC, Logan RF, Hearnshaw SA, Travis SP, Murphy MF, Palmer KR (2011). "Mortality from acute upper gastrointestinal bleeding in the United kingdom: does it display a "weekend effect"?". Am J Gastroenterol. 106 (9): 1621–8. doi:10.1038/ajg.2011.172. PMID 21606977.CS1 maint: multiple names: authors list (link): does it display a "weekend effect"? Am J Gastroenterol. 2011 Sep; 106(9): 1621-8]
- Youn YH, Park YJ, Kim JH, Jeon TJ, Cho JH, Park H (2012). "Weekend and nighttime effect on the prognosis of peptic ulcer bleeding". World J Gastroenterol. 18 (27): 3578–84. doi:10.3748/wjg.v18.i27.3578. PMC 3400860. PMID 22826623.CS1 maint: multiple names: authors list (link)
- de Groot NL, Bosman JH, Siersema PD, van Oijen MG, Bredenoord AJ (2012). "Admission time is associated with outcome of upper gastrointestinal bleeding: results of a multicentre prospective cohort study". Aliment Pharmacol Ther. 36 (5): 477–84. doi:10.1111/j.1365-2036.2012.05205.x. PMID 22747509.CS1 maint: multiple names: authors list (link)
- Abougergi MS, Travis AC, Saltzman JR (2014). "Impact of day of admission on mortality and other outcomes in upper GI hemorrhage: a nationwide analysis". Gastrointest Endosc. 80 (2): 228–35. doi:10.1016/j.gie.2014.01.043. PMID 24674354.CS1 maint: multiple names: authors list (link)
- Ahmed A, Armstrong M, Robertson I, Morris AJ, Blatchford O, Stanley AJ (2015). "Upper gastrointestinal bleeding in Scotland 2000-2010: Improved outcomes but a significant weekend effect". World J Gastroenterol. 21 (38): 10890–7. doi:10.3748/wjg.v21.i38.10890. PMC 4600590. PMID 26478680.CS1 maint: multiple names: authors list (link)
- Serrao S, Jackson C, Juma D, Babayan D, Gerson LB (2016). "In-hospital weekend outcomes in patients diagnosed with bleeding gastroduodenal angiodysplasia: a population-based study, 2000 to 2011". Gastrointest Endosc. 84 (3): 416–23. doi:10.1016/j.gie.2016.02.046. PMID 26972023.CS1 maint: multiple names: authors list (link)
- Weeda ER, Nicoll BS, Coleman CI, Sharovetskaya A, Baker WL (2016). "Association between weekend admission and mortality for upper gastrointestinal hemorrhage: an observational study and meta-analysis". Intern Emerg Med. 12 (2): 163–169. doi:10.1007/s11739-016-1522-7. PMID 27534406.CS1 maint: multiple names: authors list (link)
- Myers RP, Kaplan GG, Shaheen AM (2009). "The effect of weekend versus weekday admission on outcomes of esophageal variceal hemorrhage". Can J Gastroenterol. 23 (7): 495–501. doi:10.1155/2009/713789. PMC 2722470. PMID 19623333.CS1 maint: multiple names: authors list (link)
- Byun SJ, Kim SU, Park JY, Kim BK, Kim DY, Han KH, Chon CY, Ahn SH (2012). "Acute variceal hemorrhage in patients with liver cirrhosis: weekend versus weekday admissions". Yonsei Med J. 53 (2): 318–27. doi:10.3349/ymj.2012.53.2.318. PMC 3282972. PMID 22318819.CS1 maint: multiple names: authors list (link)
- Inamdar S, Sejpal DV, Ullah M, Trindade AJ (2016). "Weekend vs. Weekday Admissions for Cholangitis Requiring an ERCP: Comparison of Outcomes in a National Cohort". Am J Gastroenterol. 111 (3): 405–10. doi:10.1038/ajg.2015.425. PMID 26782818.CS1 maint: multiple names: authors list (link)
- Tabibian JH, Yang JD, Baron TH, Kane SV, Enders FB, Gostout CJ (2016). "Weekend Admission for Acute Cholangitis Does Not Adversely Impact Clinical or Endoscopic Outcomes". Dig. Dis. Sci. 61 (1): 53–61. doi:10.1007/s10620-015-3853-z. PMID 26391268.CS1 maint: multiple names: authors list (link)
- Hamada T, Yasunaga H, Nakai Y, Isayama H, Matsui H, Fushimi K, Koike K (2016). "No weekend effect on outcomes of severe acute pancreatitis in Japan: data from the diagnosis procedure combination database". J Gastroenterol. 51 (11): 1063–1072. doi:10.1007/s00535-016-1179-z. PMID 26897739.CS1 maint: multiple names: authors list (link)
- James MT, Wald R, Bell CM, Tonelli M, Hemmelgarn BR, Waikar SS, Chertow GM (2010). "Weekend hospital admission, acute kidney injury, and mortality". J Am Soc Nephrol. 21 (5): 845–51. doi:10.1681/ASN.2009070682. PMC 2865737. PMID 20395373.CS1 maint: multiple names: authors list (link)
- Sakhuja A, Schold JD, Kumar G, Dall A, Sood P, Navaneethan SD (2013). "Outcomes of patients receiving maintenance dialysis admitted over weekends". Am J Kidney Dis. 62 (4): 763–70. doi:10.1053/j.ajkd.2013.03.014. PMC 3783620. PMID 23669002.CS1 maint: multiple names: authors list (link)
- Haddock R, Deighan C, Thomson PC (2016). "In-patient hospital mortality patterns by day of the week: an analysis of admissions to a regional renal unit". Scott Med J. 61 (4): 179–184. doi:10.1177/0036933015619293. PMID 26610796.CS1 maint: multiple names: authors list (link)
- Orman ES, Hayashi PH, Dellon ES, Gerber DA, Barritt (2012). "Impact of nighttime and weekend liver transplants on graft and patient outcomes". Liver Transpl. 18 (5): 558–65. doi:10.1002/lt.23395. PMC 3334405. PMID 22271668.CS1 maint: multiple names: authors list (link)
- Mohan S, Foley K, Chiles MC, Dube GK, Patzer RE, Pastan SO, Crew RJ, Cohen DJ, Ratner LE (2016). "The weekend effect alters the procurement and discard rates of deceased donor kidneys in the United States". Kidney Int. 90 (1): 157–63. doi:10.1016/j.kint.2016.03.007. PMC 4912390. PMID 27182001.CS1 maint: multiple names: authors list (link)
- Anderson BM, Mytton JL, Evison F, Ferro CJ, Sharif A (2017). "Outcomes After Weekend Admission for Deceased Donor Kidney Transplantation: A Population Cohort Study". Transplantation. 101 (9): 2244–2252. doi:10.1097/TP.0000000000001522. PMID 27755501.CS1 maint: multiple names: authors list (link)
- Bejanyan N, Fu AZ, Lazaryan A, Fu R, Kalaycio M, Advani A, Sobecks R, Copelan E, Maciejewski JP, Sekeres MA (2010). "Impact of weekend admissions on quality of care and outcomes in patients with acute myeloid leukemia". Cancer. 116 (15): 3614–20. doi:10.1002/cncr.25086. PMID 20564070.CS1 maint: multiple names: authors list (link)
- Goodman EK, Reilly AF, Fisher BT, Fitzgerald J, Li Y, Seif AE, Huang YS, Bagatell R, Aplenc R (Oct 2014). "Association of weekend admission with hospital length of stay, time to chemotherapy, and risk for respiratory failure in pediatric patients with newly diagnosed leukemia at freestanding US children's hospitals". JAMA Pediatr. 168 (10): 925–31. doi:10.1001/jamapediatrics.2014.1023. PMC 4404706. PMID 25155012.CS1 maint: multiple names: authors list (link)
- Schmid M, Ghani KR, Choueiri TK, Sood A, Kapoor V, Abdollah F, Chun FK, Leow JJ, Olugbade K Jr, Sammon JD, Menon M, Kibel AS, Fisch M, Nguyen PL, Trinh QD (2015). "An evaluation of the 'weekend effect' in patients admitted with metastatic prostate cancer". BJU Int. 116 (6): 911–9. doi:10.1111/bju.12891. PMID 25099032.CS1 maint: multiple names: authors list (link)
- Lapointe-Shaw L, Abushomar H, Chen XK, Gapanenko K, Taylor C, Krzyzanowska MK, Bell CM (2016). "Care and Outcomes of Patients With Cancer Admitted to the Hospital on Weekends and Holidays: A Retrospective Cohort Study". J Natl Compr Canc Netw. 14 (7): 867–74. doi:10.6004/jnccn.2016.0091. PMID 27407127.CS1 maint: multiple names: authors list (link)
- Wichmann S, Nielsen SL, Siersma VD, Rasmussen LS (2013). "Risk factors for 48-hours mortality after prehospital treatment of opioid overdose". Emerg Med J. 30 (3): 223–5. doi:10.1136/emermed-2012-201124. PMID 22505303.CS1 maint: multiple names: authors list (link)
- Saposnik G, Baibergenova A, Bayer N, Hachinski V (2007). "Weekends: a dangerous time for having a stroke?" (PDF). Stroke. 38 (4): 1211–5. doi:10.1161/01.STR.0000259622.78616.ea. PMID 17347472.CS1 maint: multiple names: authors list (link)
- Turin TC, Kita Y, Rumana N, Ichikawa M, Sugihara H, Morita Y, Tomioka N, Okayama A, Nakamura Y, Ueshima H (2008). "Case fatality of stroke and day of the week: is the weekend effect an artifact? Takashima stroke registry, Japan (1988-2003)". Cerebrovasc Dis. 26 (6): 606–11. doi:10.1159/000165114. PMID 18946216.CS1 maint: multiple names: authors list (link)
- Tung YC, Chang GM, Chen YH (2009). "Associations of physician volume and weekend admissions with ischemic stroke outcome in Taiwan: a nationwide population-based study". Med Care. 47 (9): 1018–25. doi:10.1097/MLR.0b013e3181a81144. PMID 19648828.CS1 maint: multiple names: authors list (link)
- Kazley AS, Hillman DG, Johnston KC, Simpson KN (2010). "Hospital care for patients experiencing weekend vs weekday stroke: a comparison of quality and aggressiveness of care". Arch Neurol. 67 (1): 39–44. doi:10.1001/archneurol.2009.286. PMID 20065127.CS1 maint: multiple names: authors list (link)
- Hoh BL, Chi YY, Waters MF, Mocco J, Barker FG 2nd (2010). "Effect of weekend compared with weekday stroke admission on thrombolytic use, in-hospital mortality, discharge disposition, hospital charges, and length of stay in the Nationwide Inpatient Sample Database, 2002 to 2007". Stroke. 41 (10): 2323–8. doi:10.1161/STROKEAHA.110.591081. PMID 20724715.CS1 maint: multiple names: authors list (link)
- Fang J, Saposnik G, Silver FL, Kapral MK (2010). "Association between weekend hospital presentation and stroke fatality". Neurology. 75 (18): 1589–96. doi:10.1212/WNL.0b013e3181fb84bc. PMID 21041782.CS1 maint: multiple names: authors list (link)
- Smith EE, Shobha N, Dai D, Olson DM, Reeves MJ, Saver JL, Hernandez AF, Peterson ED, Fonarow GC, Schwamm LH (Oct 2010). "Risk score for in-hospital ischemic stroke mortality derived and validated within the Get With the Guidelines-Stroke Program". Circulation. 122 (15): 1496–504. doi:10.1161/CIRCULATIONAHA.109.932822. PMID 20876438.CS1 maint: multiple names: authors list (link)
- Ogbu UC, Westert GP, Slobbe LC, Stronks K, Arah OA (2011). "A multifaceted look at time of admission and its impact on case-fatality among a cohort of ischaemic stroke patients". J Neurol Neurosurg Psychiatry. 82 (1): 8–13. doi:10.1136/jnnp.2009.202176. PMID 20667853.CS1 maint: multiple names: authors list (link)
- McKinney JS, Deng Y, Kasner SE, Kostis JB (2011). "Comprehensive stroke centers overcome the weekend versus weekday gap in stroke treatment and mortality". Stroke. 42 (9): 2403–9. doi:10.1161/STROKEAHA.110.612317. PMID 21868723.CS1 maint: multiple names: authors list (link)
- O'Brien EC, Rose KM, Shahar E, Rosamond WD (2011). "Stroke Mortality, Clinical Presentation and Day of Arrival: The Atherosclerosis Risk in Communities (ARIC) Study". Stroke Res Treat. 2011: 1–8. doi:10.4061/2011/383012. PMC 3137964. PMID 21772968.CS1 maint: multiple names: authors list (link)
- Palmer WL, Bottle A, Davie C, Vincent CA, Aylin P (2012). "Dying for the weekend: a retrospective cohort study on the association between day of hospital presentation and the quality and safety of stroke care". Arch Neurol. 69 (10): 1296–302. doi:10.1001/archneurol.2012.1030. PMID 22777008.CS1 maint: multiple names: authors list (link)
- Albright KC, Savitz SI, Raman R, Martin-Schild S, Broderick J, Ernstrom K, Ford A, Khatri R, Kleindorfer D, Liebeskind D, Marshall R, Merino JG, Meyer DM, Rost N, Meyer BC (2012). "Comprehensive stroke centers and the 'weekend effect': the SPOTRIAS experience". Cerebrovasc Dis. 34 (5–6): 424–9. doi:10.1159/000345077. PMC 3568158. PMID 23207423.CS1 maint: multiple names: authors list (link)
- Niewada M, Jezierska-Ostapczuk A, Skowrońska M, Sarzyńska-Długosz I, Członkowska A (2012). "Weekend versus weekday admissions in Polish stroke centres -- could admission day affect prognosis in Polish ischaemic stroke patients?". Neurol Neurochir Pol. 46 (1): 15–21. doi:10.5114/ninp.2012.27209. PMID 22426758.CS1 maint: multiple names: authors list (link)
- Béjot Y, Aboa-Eboulé C, Jacquin A, Troisgros O, Hervieu M, Durier J, Osseby GV, Giroud M (2013). "Stroke care organization overcomes the deleterious 'weekend effect' on 1-month stroke mortality: a population-based study". Eur J Neurol. 20 (8): 1177–83. doi:10.1111/ene.12154. PMID 23551852.CS1 maint: multiple names: authors list (link)
- Bray BD, Ayis S, Campbell J, Cloud GC, James M, Hoffman A, Tyrrell PJ, Wolfe CD, Rudd AG (2014). "Associations between stroke mortality and weekend working by stroke specialist physicians and registered nurses: prospective multicentre cohort study". PLoS Med. 11 (8): e1001705. doi:10.1371/journal.pmed.1001705. PMC 4138029. PMID 25137386.CS1 maint: multiple names: authors list (link)
- Inoue T, Fushimi K (2015). "Weekend versus Weekday Admission and In-Hospital Mortality from Ischemic Stroke in Japan". J Stroke Cerebrovasc Dis. 24 (12): 2787–92. doi:10.1016/j.jstrokecerebrovasdis.2015.08.010. PMID 26365617.
- Roberts SE, Thorne K, Akbari A, Samuel DG, Williams JG (2015). "Mortality following Stroke, the Weekend Effect and Related Factors: Record Linkage Study". PLOS ONE. 10 (6): e0131836. Bibcode:2015PLoSO..1031836R. doi:10.1371/journal.pone.0131836. PMC 4487251. PMID 26121338.CS1 maint: multiple names: authors list (link)
- Romero Sevilla R, Portilla Cuenca JC, López Espuela F, Redondo Peñas I, Bragado Trigo I, Yerga Lorenzana B, Calle Escobar M, Gómez Gutiérrez M, Casado Naranjo I (2016). "A stroke care management system prevents outcome differences related to time of stroke unit admission". Neurologia. 31 (3): 149–56. doi:10.1016/j.nrl.2015.07.011. PMID 26385014.CS1 maint: multiple names: authors list (link)
- Turner M, Barber M, Dodds H, Dennis M, Langhorne P, Macleod MJ (2015). "Stroke patients admitted within normal working hours are more likely to achieve process standards and to have better outcomes". J Neurol Neurosurg Psychiatry. 87 (2): 138–43. doi:10.1136/jnnp-2015-311273. PMC 4752676. PMID 26285585.CS1 maint: multiple names: authors list (link)
- Cho KH, Park EC, Nam CM, Choi Y, Shin J, Lee SG (2016). "Effect of Weekend Admission on In-Hospital Mortality in Patients with Ischemic Stroke: An Analysis of Korean Nationwide Claims Data from 2002 to 2013". J Stroke Cerebrovasc Dis. 25 (2): 419–27. doi:10.1016/j.jstrokecerebrovasdis.2015.10.014. PMID 26654666.CS1 maint: multiple names: authors list (link)
- Hsieh CY, Lin HJ, Chen CH, Li CY, Chiu MJ, Sung SF (2016). ""Weekend effect" on stroke mortality revisited: Application of a claims-based stroke severity index in a population-based cohort study". Medicine (Baltimore). 95 (25): e4046. doi:10.1097/MD.0000000000004046. PMC 4998342. PMID 27336904.CS1 maint: multiple names: authors list (link)
- Ansa V, Otu A, Oku A, Njideoffor U, Nworah C, Odigwe C (2016). "Patient outcomes following after-hours and weekend admissions for cardiovascular disease in a tertiary hospital in Calabar, Nigeria". Cardiovasc J Afr. 27 (5): 328–332. doi:10.5830/CVJA-2016-025. PMC 5370317. PMID 27080145.CS1 maint: multiple names: authors list (link)
- Adil MM, Vidal G, Beslow LA (2016). "Weekend Effect in Children With Stroke in the Nationwide Inpatient Sample". Stroke. 47 (6): 1436–43. doi:10.1161/STROKEAHA.116.013453. PMID 27118791.CS1 maint: multiple names: authors list (link)
- Goldacre MJ, Maisonneuve JJ (2013). "Mortality from meningococcal disease by day of the week: English national linked database study". J Public Health (Oxf). 35 (3): 413–21. doi:10.1093/pubmed/fdt004. PMID 23378233.
- Crowley RW, Yeoh HK, Stukenborg GJ, Ionescu AA, Kassell NF, Dumont AS (2009). "Influence of weekend versus weekday hospital admission on mortality following subarachnoid hemorrhage. Clinical article". J Neurosurg. 111 (1): 60–6. doi:10.3171/2008.11.JNS081038. PMID 19231928.CS1 maint: multiple names: authors list (link)
- Jiang F, Zhang JH, Qin X (2011). "Weekend effects" in patients with intracerebral hemorrhage. Acta Neurochir Suppl. Acta Neurochirurgica Supplementum. 111. pp. 333–6. doi:10.1007/978-3-7091-0693-8_55. ISBN 978-3-7091-0692-1. PMID 21725777.CS1 maint: multiple names: authors list (link)
- Patel AA, Mahajan A, Benjo A, Pathak A, Kar J, Jani VB, Annapureddy N, Agarwal SK, Sabharwal MS, Simoes PK, Konstantinidis I, Yacoub R, Javed F, El Hayek G, Menon MC, Nadkarni GN (2015). "A Nationwide Analysis of Outcomes of Weekend Admissions for Intracerebral Hemorrhage Shows Disparities Based on Hospital Teaching Status". Neurohospitalist. 6 (2): 51–8. doi:10.1177/1941874415601164. PMC 4802773. PMID 27053981.CS1 maint: multiple names: authors list (link)
- Hashimoto S, Maeda M, Yamakita J, Nakamura Y (1990). "Effects of zinc oxide-eugenol on leucocyte number and lipoxygenase products in artificially inflamed rat dental pulp". Arch Oral Biol. 35 (2): 87–93. doi:10.1016/0003-9969(90)90168-a. PMID 2111694.CS1 maint: multiple names: authors list (link)
- Deshmukh H, Hinkley M, Dulhanty L, Patel HC, Galea JP (2016). "Effect of weekend admission on in-hospital mortality and functional outcomes for patients with acute subarachnoid haemorrhage (SAH)". Acta Neurochir (Wien). 158 (5): 829–35. doi:10.1007/s00701-016-2746-z. PMC 4826657. PMID 26928730.CS1 maint: multiple names: authors list (link)
- Busl KM, Prabhakaran S (2013). "Predictors of mortality in nontraumatic subdural hematoma". J Neurosurg. 119 (5): 1296–301. doi:10.3171/2013.4.JNS122236. PMID 23746103.
- Rumalla K, Reddy AY, Mittal MK (2017). "Traumatic subdural hematoma: Is there a weekend effect?". Clin Neurol Neurosurg. 154: 67–73. doi:10.1016/j.clineuro.2017.01.014. PMID 28129634.CS1 maint: multiple names: authors list (link)
- Dasenbrock HH, Pradilla G, Witham TF, Gokaslan ZL, Bydon A (2012). "The impact of weekend hospital admission on the timing of intervention and outcomes after surgery for spinal metastases". Neurosurgery. 70 (3): 586–93. doi:10.1227/NEU.0b013e318232d1ee. PMID 21869727.CS1 maint: multiple names: authors list (link)
- Schneider EB, Hirani SA, Hambridge HL, Haut ER, Carlini AR, Castillo RC, Efron DT, Haider AH (2012). "Beating the weekend trend: increased mortality in older adult traumatic brain injury (TBI) patients admitted on weekends". J Surg Res. 177 (2): 295–300. doi:10.1016/j.jss.2012.06.022. PMID 22795343.CS1 maint: multiple names: authors list (link)
- Nandyala SV, Marquez-Lara A, Fineberg SJ, Schmitt DR, Singh K (2013). "Comparison of perioperative outcomes and cost of spinal fusion for cervical trauma: weekday versus weekend admissions". Spine. 38 (25): 2178–83. doi:10.1097/BRS.0000000000000020. PMID 24285275.CS1 maint: multiple names: authors list (link)
- Desai V, Gonda D, Ryan SL, Briceño V, Lam SK, Luerssen TG, Syed SH, Jea A (2015). "The effect of weekend and after-hours surgery on morbidity and mortality rates in pediatric neurosurgery patients". J Neurosurg Pediatr. 16 (6): 726–31. doi:10.3171/2015.6.PEDS15184. PMID 26406160.CS1 maint: multiple names: authors list (link)
- Tanenbaum JE, Lubelski D, Rosenbaum BP, Thompson NR, Benzel EC, Mroz TE (2016). "Predictors of outcomes and hospital charges following atlantoaxial fusion". Spine J. 16 (5): 608–18. doi:10.1016/j.spinee.2015.12.090. PMC 5506776. PMID 26792199.CS1 maint: multiple names: authors list (link)
- Attenello FJ, Christian E, Wen T, Cen S, Zada G, Kiehna EN, Krieger MD, McComb JG, Mack WJ (2015). "Reevaluating the weekend effect on patients with hydrocephalus undergoing operative shunt intervention". J Neurosurg Pediatr. 17 (2): 1–7. doi:10.3171/2015.6.PEDS15109. PMID 26544080.CS1 maint: multiple names: authors list (link)
- Linzey JR, Sabbagh MA, Pandey AS (2016). "104 The Effect of Surgical Start Time and Day of the Week on Morbidity and Mortality for Neurological Surgeries". Neurosurgery. 63 Suppl 1: 144. doi:10.1227/01.neu.0000489675.22357.39. PMID 27399384.CS1 maint: multiple names: authors list (link)
- Ferguson S, Chesnut DB (1978). "A magnetic resonance spin label study of human dental enamel". Arch Oral Biol. 23 (2): 85–90. doi:10.1016/0003-9969(78)90144-9. PMID 207247.
- Eisenberg R (1976). "The specificity and polyvalency of binding of a monoclonal rheumatoid factor". Immunochemistry. 13 (4): 355–9. doi:10.1016/0019-2791(76)90347-5. PMID 59692."Newcastle survey of deaths in early childhood 1974/76, with special reference to sudden unexpected deaths. Working party for early childhood deaths in Newcastle". Archives of Disease in Childhood. 52 (11): 828–835. November 1977. doi:10.1136/adc.52.11.828. PMC 1544816. PMID 596921.]
- Hendry RA (1981). "The weekend--a dangerous time to be born?". Br J Obstet Gynaecol. 88 (12): 1200–3. doi:10.1111/j.1471-0528.1981.tb01197.x. PMID 7306474.
- Mangold WD (1981). "Neonatal mortality by the day of the week in the 1974-75 Arkansas live birth cohort". Am J Public Health. 71 (6): 601–5. doi:10.2105/ajph.71.6.601. PMC 1619835. PMID 7235098.]]
- Mathers CD (1983). "Births and perinatal deaths in Australia: variations by day of week". J Epidemiol Community Health. 37 (1): 57–62. doi:10.1136/jech.37.1.57. PMC 1052257. PMID 6683744.
- Hamilton P, Restrepo E (2003). "Weekend birth and higher neonatal mortality: a problem of patient acuity or quality of care?". J Obstet Gynecol Neonatal Nurs. 32 (6): 724–33. doi:10.1177/0884217503258306. PMID 14649592.
- Gould JB, Qin C, Marks AR, Chavez G (2003). "Neonatal mortality in weekend vs weekday births". JAMA. 289 (22): 2958–62. doi:10.1001/jama.289.22.2958. PMID 12799403.CS1 maint: multiple names: authors list (link)
- Luo ZC, Liu S, Wilkins R, Kramer MS (2004). "Risks of stillbirth and early neonatal death by day of week". CMAJ. 170 (3): 337–41. PMC 331383. PMID 14757669.CS1 maint: multiple names: authors list (link)
- Salihu HM, Ibrahimou B, August EM, Dagne G (2012). "Risk of infant mortality with weekend versus weekday births: a population-based study". J Obstet Gynaecol Res. 38 (7): 973–9. doi:10.1111/j.1447-0756.2011.01818.x. PMID 22487462.CS1 maint: multiple names: authors list (link)
- Ibrahimou B, Salihu HM, English G, Anozie C, Lartey G, Dagne G (2012). "Twins born over weekends: are they at risk for elevated infant mortality?". Arch Gynecol Obstet. 286 (6): 1349–55. doi:10.1007/s00404-012-2463-7. PMID 22797696.CS1 maint: multiple names: authors list (link)
- Palmer WL, Bottle A, Aylin P (2015). "Association between day of delivery and obstetric outcomes: observational study". BMJ. 351: h5774. doi:10.1136/bmj.h5774. PMC 4658392. PMID 26602245.CS1 maint: multiple names: authors list (link)
- Mitchell EA, Stewart AW (1988). "Deaths from sudden infant death syndrome on public holidays and weekends". Aust N Z J Med. 18 (7): 861–3. doi:10.1111/j.1445-5994.1988.tb01646.x. PMID 3250410.
- Goldstein SD, Papandria DJ, Aboagye J, Salazar JH, Van Arendonk K, Al-Omar K, Ortega G, Sacco Casamassima MG, Abdullah F (2014). "The "weekend effect" in pediatric surgery - increased mortality for children undergoing urgent surgery during the weekend". J Pediatr Surg. 49 (7): 1087–91. doi:10.1016/j.jpedsurg.2014.01.001. PMID 24952794.CS1 maint: multiple names: authors list (link)
- Burstein B, Fauteux-Lamarre E, As AB (2016). "Increased morbidity associated with weekend paediatric road traffic injuries: 10-year analysis of trauma registry data". Injury. 47 (6): 1236–41. doi:10.1016/j.injury.2016.02.021. PMID 27084114.CS1 maint: multiple names: authors list (link)
- Worni M, Østbye T, Gandhi M, Rajgor D, Shah J, Shah A, Pietrobon R, Jacobs DO, Guller U (2012). "Laparoscopic appendectomy outcomes on the weekend and during the week are no different: a national study of 151,774 patients" (PDF). World J Surg. 36 (7): 1527–33. doi:10.1007/s00268-012-1550-z. PMID 22411091.CS1 maint: multiple names: authors list (link)
- Worni M, Schudel IM, Østbye T, Shah A, Khare A, Pietrobon R, Thacker JK, Guller U (2012). "Worse outcomes in patients undergoing urgent surgery for left-sided diverticulitis admitted on weekends vs weekdays: a population-based study of 31 832 patients". Arch Surg. 147 (7): 649–55. doi:10.1001/archsurg.2012.825. PMID 22802061.CS1 maint: multiple names: authors list (link)
- McVay DP, Walker AS, Nelson DW, Porta CR, Causey MW, Brown TA (2014). "The weekend effect: does time of admission impact management and outcomes of small bowel obstruction?". Gastroenterol Rep (Oxf). 2 (3): 221–5. doi:10.1093/gastro/gou043. PMC 4124276. PMID 25008263.CS1 maint: multiple names: authors list (link)
- Orman ES, Hayashi PH, Dellon ES, Gerber DA, Barritt AS 4th (2012). "Impact of nighttime and weekend liver transplants on graft and patient outcomes". Liver Transpl. 18 (5): 558–65. doi:10.1002/lt.23395. PMC 3334405. PMID 22271668.CS1 maint: multiple names: authors list (link)
- Hoehn RS, Hanseman DJ, Chang AL, Daly MC, Ertel AE, Abbott DE, Shah SA, Paquette IM. Surgeon Characteristics Supersede Hospital Characteristics in Mortality After Urgent Colectomy. J Gastrointest Surg. 2017 Jan; 21(1): 23-32
- Carr BG, Reilly PM, Schwab CW, Branas CC, Geiger J, Wiebe DJ (2011). "Weekend and night outcomes in a statewide trauma system". Arch Surg. 146 (7): 810–7. doi:10.1001/archsurg.2011.60. PMID 21422328.CS1 maint: multiple names: authors list (link)
- Daugaard CL, Jørgensen HL, Riis T, Lauritzen JB, Duus BR, van der Mark S (2012). "Is mortality after hip fracture associated with surgical delay or admission during weekends and public holidays? A retrospective study of 38,020 patients". Acta Orthop. 83 (6): 609–13. doi:10.3109/17453674.2012.747926. PMC 3555458. PMID 23140106.CS1 maint: multiple names: authors list (link)
- Thomas CJ, Smith RP, Uzoigwe CE, Braybrooke JR (2014). "The weekend effect: short-term mortality following admission with a hip fracture". Bone Joint J. 96-B (3): 373–8. doi:10.1302/0301-620X.96B3.33118. PMID 24589794.CS1 maint: multiple names: authors list (link)
- Boylan MR, Rosenbaum J, Adler A, Naziri Q, Paulino CB (2015). "Hip Fracture and the Weekend Effect: Does Weekend Admission Affect Patient Outcomes?". Am J Orthop (Belle Mead NJ). 44 (10): 458–64. PMID 26447407.CS1 maint: multiple names: authors list (link)
- Kristiansen NS, Kristensen PK, Nørgård BM, Mainz J, Johnsen SP (2016). "Off-hours admission and quality of hip fracture care: a nationwide cohort study of performance measures and 30-day mortality". Int J Qual Health Care. 28 (3): 324–31. doi:10.1093/intqhc/mzw037. PMID 27097886.CS1 maint: multiple names: authors list (link)
- Dei Giudici L, Giampaolini N, Panfighi A, Marinelli M, Procaccini R, Gigante A (2015). "Orthopaedic Timing in Polytrauma in a Second Level Emergency Hospital. An Overrated Problem?". Open Orthop J. 9: 296–302. doi:10.2174/1874325001509010296. PMC 4541330. PMID 26312113.CS1 maint: multiple names: authors list (link)
- Giannoudis V, Panteli M, Giannoudis PV. Management of polytrauma patients in the UK: Is there a 'weekend effect'? Injury. 2016 Nov; 47(11): 2385-2390
- Metcalfe D, Perry DC, Bouamra O, Salim A, Lecky FE, Woodford M, Edwards A, Costa ML. Is there a 'weekend effect' in major trauma? Emerg Med J. 2016 Dec; 33(12): 836-842
- Gallerani M, Imberti D, Bossone E, Eagle KA, Manfredini R (2012). "Higher mortality in patients hospitalized for acute aortic rupture or dissection during weekends". J Vasc Surg. 55 (5): 1247–54. doi:10.1016/j.jvs.2011.11.133. PMID 22542339.CS1 maint: multiple names: authors list (link)
- Groves EM, Khoshchehreh M, Le C, Malik S (2014). "Effects of weekend admission on the outcomes and management of ruptured aortic aneurysms". J Vasc Surg. 60 (2): 318–24. doi:10.1016/j.jvs.2014.02.052. PMC 4121436. PMID 24709439.CS1 maint: multiple names: authors list (link)
- Orandi BJ, Selvarajah S, Orion KC, Lum YW, Perler BA, Abularrage CJ (2014). "Outcomes of nonelective weekend admissions for lower extremity ischemia". J Vasc Surg. 60 (6): 1572–9.e1. doi:10.1016/j.jvs.2014.08.091. PMID 25441678.CS1 maint: multiple names: authors list (link)
- Arora S, Panaich SS, Patel N, Patel N, Lahewala S, Solanki S, Patel P, Patel A, Manvar S, Savani C, Tripathi B, Thakkar B, Jhamnani S, Singh V, Patel S, Patel J, Bhimani R, Mohamad T, Remetz MS, Curtis JP, Attaran RR, Grines C, Mena CI, Cleman M, Forrest J, Badheka AO (2015). "Impact of Hospital Volume on Outcomes of Lower Extremity Endovascular Interventions (Insights from the Nationwide Inpatient Sample [2006 to 2011])". Am J Cardiol. 116 (5): 791–800. doi:10.1016/j.amjcard.2015.05.050. PMID 26100585.CS1 maint: multiple names: authors list (link)]). Am J Cardiol. 2015 Sep 1; 116(5): 791–800]
- Tadisina KK, Chopra K, Singh DP (2015). "The "weekend effect" in plastic surgery: analyzing weekday versus weekend admissions in body contouring procedures from 2000 to 2010". Aesthet Surg J. 35 (8): 995–8. doi:10.1093/asj/sjv088. PMID 26019238.CS1 maint: multiple names: authors list (link)
- Patel A, Foden N, Rachmanidou A (2016). "Is weekend surgery a risk factor for post-tonsillectomy haemorrhage?". J Laryngol Otol. 130 (8): 763–7. doi:10.1017/S0022215116008161. PMID 27292442.CS1 maint: multiple names: authors list (link)
- Sayari AJ, Tashiro J, Wang B, Perez EA, Lasko DS, Sola JE (2016). "Weekday vs. weekend repair of esophageal atresia and tracheoesophageal fistula". J Pediatr Surg. 51 (5): 739–42. doi:10.1016/j.jpedsurg.2016.02.014. PMID 26932247.CS1 maint: multiple names: authors list (link)
- Blackwell RH, Barton GJ, Kothari AN, Zapf MA, Flanigan RC, Kuo PC, Gupta GN (2016). "Early Intervention during Acute Stone Admissions: Revealing "The Weekend Effect" in Urological Practice". J Urol. 196 (1): 124–30. doi:10.1016/j.juro.2016.01.056. PMC 5207476. PMID 26804754.CS1 maint: multiple names: authors list (link)
- Aylin P (2015). "Making sense of the evidence for the "weekend effect"". BMJ. 351: h4652. doi:10.1136/bmj.h4652. hdl:10044/1/42383. PMID 26342692.
- RCP Council (November 2010). "RCP Position Statement Care of Medical Patients Out of Hours" (PDF).
- Association of Royal Medical Colleges (November 2013). "Seven Day Consultant Present Care Implementation".
- Flynn, Paul (2013-02-21). "Should the NHS work at weekends as it does in the week? No". The BMJ. 346: f622. doi:10.1136/bmj.f622. ISSN 1756-1833. PMID 23430215.
- Freemantle, Nick; Ray, Daniel; McNulty, David; Rosser, David; Bennett, Simon; Keogh, Bruce E.; Pagano, Domenico (2015-09-05). "Increased mortality associated with weekend hospital admission: a case for expanded seven day services?". The BMJ. 351: h4596. doi:10.1136/bmj.h4596. ISSN 1756-1833. PMID 26342923.
- Donnelly, Laura (2015-09-06). "'The weekend effect' means 11,000 extra NHS deaths a year". Retrieved 2015-10-07.
- Weaver, Matthew; Campbell, Denis (2015-10-07). "The Hunt file: doctors' dossier of patients 'put at risk' by health secretary". the Guardian. Retrieved 2015-10-07.
- "Re: Increased mortality associated with weekend hospital admission: a case for expanded seven day services?". The BMJ. 352: i1762. 2015-10-12. doi:10.1136/bmj.i1762. PMID 27025883.
- "Contract reform for consultants and doctors and dentists in training – supporting healthcare services seven days a week - Publications - GOV.UK". www.gov.uk. Retrieved 2015-10-07.
- Choices, NHS. "My NHS - NHS Choices". www.nhs.uk. Retrieved 2015-10-07.
- "BMA - DDRB Recommendations - Analysis For Juniors │ British Medical Association". bma.org.uk. Retrieved 2015-10-07.
- "Junior Doctors descend on Westminster in protest at 'unsafe' working contracts". Express.co.uk. 2015-09-29. Retrieved 2015-10-07.
- "Junior doctors plan protest against "unfair and unsafe" contract shake-up facing colleagues in England". Herald Scotland. Retrieved 2015-10-07.
- Swinford, Steven (2015-07-15). "Consultants must work weekends to save lives, Jeremy Hunt says". Retrieved 2015-10-07.
- "Petition for MPs to debate a vote of no confidence in Jeremy Hunt hits 100,000 in 24 hours". The Independent. 2015-07-21. Retrieved 2015-10-07.
- Gan, Hoong-Wei; Wong, Danny Jon Nian; Dean, Benjamin John Floyd; Hall, Alistair Scott (2015-08-10). "Do expanded seven-day NHS services improve clinical outcomes? Analysis of comparative institutional performance from the "NHS Services, Seven Days a Week" project 2013–2016". BMC Health Services Research. 17 (1): 552. doi:10.1186/s12913-017-2505-8. PMC 5553994. PMID 28797268.