Biphasic and polyphasic sleep
Biphasic sleep (or diphasic, bimodal or bifurcated sleep) is the practice of sleeping during two periods over the course of 24 hours, while polyphasic sleep refers to sleeping two or more times. Each of these is in contrast to monophasic sleep, which is one period of sleep within 24 hours. Segmented sleep and divided sleep may refer to polyphasic or biphasic sleep, but may also refer to interrupted sleep, where the sleep has one or several shorter periods of wakefulness. A common form of biphasic sleep is the Everyman 1 schedule, which usually contains one six hour block of "core sleep" and one 20 minute nap. Common forms of polyphasic sleep are the Everyman 2 schedule; which is composed of a 4.5 hour block of core sleep with two 20 minute naps—and the Everyman 3 schedule; which is composed of a 3 hour block of core sleep and three 20 minute naps.
The term polyphasic sleep was first used in the early 20th century by psychologist J. S. Szymanski, who observed daily fluctuations in activity patterns (see Stampi 1992). It is primarily used in the modern day by people that experiment with biphasic and polyphasic schedules to achieve more time awake each day. Sleep schedules which provide the required amount of SWS cycles, and REM cycles are reported to be sustainable once a person has adapted to them, even though adaptation can be uncomfortable and difficult depending on the schedule. Adaptation takes about 4-8 weeks for most schedules. Many people do not sustain these sleep schedules for very long as doing so tends to conflict with professional and personal relationships, although the schedules have not been proven to be unhealthy. More physiologically demanding polyphasic schedules such as the Uberman schedule and the Dymaxion schedule, which eliminate all cycles except for REM cycles from the sleep schedule, have not been proven to be remotely sustainable at all.[better source needed]
Organization factors and example schedulesEdit
People who sleep on biphasic or polyphasic schedules adhere to strict guidelines as to allow their bodies to adjust to and sustain the schedule. These include but are not limited to,
- Elimination of blue light 2 hours before core sleep and 30 minutes before 20 minute naps
- Elimination of food 2 hours before core sleep and 1 hour before 20 minute naps
- Sleeping and waking up at the same times every day
- Placing core sleeps and naps at specific circadian-sensitive times of the day, or else use artificial lighting to engineer circadian perception to the desired result
- Age restrictions on sleep schedule hours: <16 years of age = <7.5 hours. 16-17 years of age = <6.3 hours. 18-21 years of age = <5 hours. 21+ years of age = <4 hours.
- Adaptation difficulty: Easy
- Total time asleep: 7 hours
- Quotient: Two core sleeps: both 3.5 hours
- Ideal sleep setup: One core sleep from 21:30 to 01:00, the other from 04:00 to 07:30
- Adaptation difficulty: Easy
- Total time asleep: 6 hours 30 minutes
- Quotient: One 5 hour core sleep and one 90 minute core sleep
- Ideal sleep setup: 5 hour core sleep from 01:00 to 06:00, 90 minute core sleep from 14:30 to 16:00
- Adaptation difficulty: Moderate
- Total time asleep: 4 hours 30 minutes
- Quotient: Three 1.5 hrs segments of sleep
- Ideal sleep setup: One segment from 05:30 to 07:00, one segment from 14:00 to 15:30, another segment 22:00 to 23:30.
- Adaptation difficulty: Easy
- Total time asleep: 6 hours 20 minutes
- Quotient: One 6 hour core sleep and one 20 minute nap
- Ideal sleep setup: 6 hour core sleep from 23:00 to 05:00, 20 minute nap from 13:00 to 13:20
- Adaptation difficulty: Moderate
- Total time asleep: 5 hours 10 minutes
- Quotient: One 4.5 hour core sleep and two 20 minute naps
- Ideal sleep setup: 4.5 hour core sleep from 23:00 to 03:30, 20 minute nap from 08:00 to 08:20, 20 minute nap from 14:30 to 14:50
- Adaptation difficulty: Hard
- Total time asleep: 4 hours
- Quotient: One 3 hour core and three 20 minute naps
- Ideal sleep setup: 3 hour core sleep from 21:00 to 00:00, 20 minute nap from 04:10 to 04:30, 20 minute nap from 08:10 to 08:30, 20 minute nap from 14:40 to 15:00
Sleep Spindles, K Complexes, Sleep Pressure, and RepartitioningEdit
Sleep schedules which do not include NREM1 and NREM2 are plausibly healthy. NREM1 is a merely transitory phase where alpha waves in the brain disappear and theta waves appear. NREM2 includes of activity sleep spindles and K complexes, but these are mostly included in SWS. Non-SWS containing polyphasic sleep schedules (Uberman, Dymaxion, etc.) are unhealthy for this reason. It is unknown whether or not NREM2 is a necessary stage of sleep or if when removing such a stage, the sleep spindle and K complex activity moves over into the SWS cycles.
Sleep Onset REM is what happens when a person has been awake for a certain amount of time contradictory to how their circadian rhythm expects it to be, and when they fall asleep they enter REM sleep rather than light sleep. As a result of having been awake or not awake in various increments of time relative to the circadian clock of an individual, one will experience and consider what is referred to as "sleep pressure". The entire process of adapting to a bi/polyphasic sleep schedule is that of repartitioning the way the brain interacts with sleep cycles through temporary sleep deprivation and usage of sleep pressure. When adaptation is reached, one is no longer sleep deprived.[better source needed]
Campbell and MurphyEdit
In their 2006 paper "The Nature of Spontaneous Sleep Across Adulthood", Campbell and Murphy studied sleep timing and quality in young, middle-aged, and older adults. They found that, in free-running conditions, the average duration of major nighttime sleep was significantly longer in young adults than in the other groups. The paper states further:
Whether such patterns are simply a response to the relatively static experimental conditions, or whether they more accurately reflect the natural organization of the human sleep/wake system, compared with that which is exhibited in daily life, is open to debate. However, the comparative literature strongly suggests that shorter, polyphasically-placed sleep is the rule, rather than the exception, across the entire animal kingdom (Campbell and Tobler, 1984; Tobler, 1989). There is little reason to believe that the human sleep/wake system would evolve in a fundamentally different manner. That people often do not exhibit such sleep organization in daily life merely suggests that humans have the capacity (often with the aid of stimulants such as caffeine or increased physical activity) to overcome the propensity for sleep when it is desirable, or is required, to do so.
Piotr Woźniak's Criticism of the Uberman scheduleEdit
Piotr Woźniak considers the theory behind severe reduction of total sleep time by way of short naps unsound, arguing that there is no brain control mechanism that would make it possible to adapt to the "multiple naps" system. Woźniak expresses concern that the ways in which the polyphasic sleepers' attempt to limit total sleep time, restrict time spent in the various stages of the sleep cycle, and disrupt their circadian rhythms, will eventually cause them to suffer the same negative effects as those with other forms of sleep deprivation and circadian rhythm sleep disorder. Woźniak further claims to have scanned the blogs of polyphasic sleepers and found that they have to choose an "engaging activity" again and again just to stay awake and that polyphasic sleep does not improve one's learning ability or creativity.
Accounts in different entitiesEdit
The U.S. military has studied fatigue countermeasures. An Air Force report states:
Each individual nap should be long enough to provide at least 45 continuous minutes of sleep, although longer naps (2 hours) are better. In general, the shorter each individual nap is, the more frequent the naps should be (the objective remains to acquire a daily total of 8 hours of sleep).
Canadian Marine pilotsEdit
Similarly, the Canadian Marine pilots in their trainer's handbook report that:
Research on napping shows that 10- to 20-minute naps at regular intervals during the day can help relieve some of the sleep deprivation and thus maintain ... performance for several days. However, researchers caution that levels of performance achieved using ultrashort sleep (short naps) to temporarily replace normal sleep are always well below that achieved when fully rested.
NASA, in cooperation with the National Space Biomedical Research Institute, has funded research on napping. Despite NASA recommendations that astronauts sleep eight hours a day when in space, they usually have trouble sleeping eight hours at a stretch, so the agency needs to know about the optimal length, timing and effect of naps. Professor David Dinges of the University of Pennsylvania School of Medicine led research in a laboratory setting on sleep schedules which combined various amounts of "anchor sleep", ranging from about four to eight hours in length, with no nap or daily naps of up to 2.5 hours. Longer naps were found to be better, with some cognitive functions benefiting more from napping than others. Vigilance and basic alertness benefited the least while working memory benefited greatly. Naps in the individual subjects' biological daytime worked well, but naps in their nighttime were followed by much greater sleep inertia lasting up to an hour.
Italian Air ForceEdit
The Italian Air Force (Aeronautica Militare Italiana) also conducted experiments for their pilots. In schedules involving night shifts and fragmentation of duty periods through the entire day, a sort of polyphasic sleeping schedule was studied. Subjects were to perform two hours of activity followed by four hours of rest (sleep allowed), this was repeated four times throughout the 24-hour day. Subjects adopted a schedule of sleeping only during the final three rest periods in linearly increasing duration. The AMI published findings that "total sleep time was substantially reduced as compared to the usual 7–8 hour monophasic nocturnal sleep" while "maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps." EEG microsleeps are measurable and usually unnoticeable bursts of sleep in the brain while a subject appears to be awake. Nocturnal sleepers who sleep poorly may be heavily bombarded with microsleeps during waking hours, limiting focus and attention.
In order to gain more time awake in the day, Buckminster Fuller reportedly advocated a regimen consisting of 30-minute naps every six hours. The short article about Fuller's nap schedule in Time in 1943, which also refers to such a schedule as "intermittent sleeping", says that he maintained it for two years, and further notes "he had to quit because his schedule conflicted with that of his business associates, who insisted on sleeping like other men."
Claudio Stampi, as a result of his interest in long-distance solo boat racing, has studied the systematic timing of short naps as a means of ensuring optimal performance in situations where extreme sleep deprivation is inevitable, but he does not advocate ultrashort napping as a lifestyle. Scientific American Frontiers (PBS) has reported on Stampi's 49-day experiment where a young man napped for a total of three hours per day. It purportedly shows that all stages of sleep were included. Stampi has written about his research in his book Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep (1992). In 1989 he published results of a field study in the journal Work & Stress, concluding that "polyphasic sleep strategies improve prolonged sustained performance" under continuous work situations. In addition, other long-distance solo sailors have documented their techniques for maximizing wake time on the open seas. One account documents the process by which a solo sailor broke his sleep into between 6 and 7 naps per day. The naps would not be placed equiphasically, instead occurring more densely during night hours.
One classic cultural example of a biphasic sleep pattern is the practice of siesta, which is a nap taken in the early afternoon, often after the midday meal. Such a period of sleep is a common tradition in some countries, particularly those where the weather is warm. The siesta is historically common throughout the Mediterranean and Southern Europe. It is the traditional daytime sleep of China, India, South Africa, Italy, Spain and, through Spanish influence, the Philippines and many Hispanic American countries. Benefits include boost in cognitive function and stress reduction.
Interrupted sleep is a primarily biphasic sleep pattern where two periods of nighttime sleep are punctuated by a period of wakefulness. This is what is called in scheduling terms the "segmented schedule". Along with a nap in the day, it has been argued that this is the natural pattern of human sleep in long winter nights. A case has been made that maintaining such a sleep pattern may be important in regulating stress.
Historian A. Roger Ekirch has argued that before the Industrial Revolution, interrupted sleep was dominant in Western civilization. He draws evidence from more than 500 references to a segmented sleeping pattern in documents from the ancient, medieval, and modern world. Other historians, such as Craig Koslofsky, have endorsed Ekirch's analysis.
According to Ekirch's argument, adults typically slept in two distinct phases, bridged by an intervening period of wakefulness of approximately one hour. This time was used to pray and reflect, and to interpret dreams, which were more vivid at that hour than upon waking in the morning. This was also a favorite time for scholars and poets to write uninterrupted, whereas still others visited neighbors, engaged in sexual activity, or committed petty crime.:311–323
The human circadian rhythm regulates the human sleep-wake cycle of wakefulness during the day and sleep at night. Ekirch suggests that it is due to the modern use of electric lighting that most modern humans do not practice interrupted sleep, which is a concern for some writers. Superimposed on this basic rhythm is a secondary one of light sleep in the early afternoon.
The modern assumption that consolidated sleep with no awakenings is the normal and correct way for human adults to sleep, may lead people to consult their doctors fearing they have maintenance insomnia or other sleep disorders. If Ekirch's hypothesis is correct, their concerns might best be addressed by reassurance that their sleep conforms to historically natural sleep patterns.
Ekirch has found that the two periods of night sleep were called "first sleep" (occasionally "dead sleep") and "second sleep" (or "morning sleep") in medieval England. He found that first and second sleep were also the terms in the Romance languages, as well as in the language of the Tiv of Nigeria. In French, the common term was premier sommeil or premier somme; in Italian, primo sonno; in Latin, primo somno or concubia nocte.:301–302 He found no common word in English for the period of wakefulness between, apart from paraphrases such as first waking or when one wakes from his first sleep and the generic watch in its old meaning of being awake. In old French an equivalent generic term is dorveille, a portmanteau of the French words dormir (to sleep) and veiller (to be awake).
Because members of modern industrialised societies, with later evening hours facilitated by electric lighting, mostly do not practice interrupted sleep, Ekirch suggests that they may have misinterpreted and mistranslated references to it in literature. Common modern interpretations of the term first sleep are "beauty sleep" and "early slumber". A reference to first sleep in the Odyssey was translated as "first sleep" in the seventeenth century, but, if Ekirch's hypothesis is correct, was universally mistranslated in the twentieth.:303
In his 1992 study "In short photoperiods, human sleep is biphasic", Thomas Wehr had seven healthy men confined to a room for fourteen hours of darkness daily for a month. At first the participants slept for about eleven hours, presumably making up for their sleep debt. After this the subjects began to sleep much as people in pre-industrial times were claimed to have done. They would sleep for about four hours, wake up for two to three hours, then go back to bed for another four hours. They also took about two hours to fall asleep.
Another example of polyphasic sleep is found in patients with irregular sleep-wake syndrome, a circadian rhythm sleep disorder which usually is caused by neurological abnormality, head injury or dementia. Much more common examples are the sleep of human infants, elders, and of many animals. It is common in many animals, and is believed to be the ancestral sleep state for mammals, although simians tend to sleep monophasically.
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