Polyphasic sleep

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Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours, in contrast to monophasic sleep, which is one period of sleep within 24 hours. Biphasic (or diphasic, bifurcated, or bimodal) sleep refers to two periods, while polyphasic usually means more than two. [1] 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, as was the norm for night sleep in pre-industrial societies.

Contents

A common form of biphasic or polyphasic sleep includes a nap, which is a short period of sleep, typically taken between the hours of 9 am and 9 pm as an adjunct to the usual nocturnal sleep period. Napping behavior during daytime hours is the simplest form of polyphasic sleep, especially when the naps are taken on a daily basis.

The term polyphasic sleep was first used in the early 20th century by psychologist J. S. Szymanski, who observed daily fluctuations in activity patterns. [2] It does not imply any particular sleep schedule. The circadian rhythm disorder known as irregular sleep-wake syndrome is an example of polyphasic sleep in humans. Polyphasic sleep is common in many animals, and is believed to be the ancestral sleep state for mammals, although simians are monophasic. [3]

The term polyphasic sleep is also used by an online community that experiments with alternative sleeping schedules in an attempt to increase productivity. There is no scientific evidence that this practice is effective or beneficial. [4] [5]

Biphasic sleep

Biphasic sleep (also referred to as segmented sleep, or bimodal sleep) is a pattern of sleep which is divided into two segments, or phases, in a 24-hour period.

Mid-day Nap Sleep Patterne Biphasic.svg
Mid-day Nap Sleep Patterne

Single nap (siesta)

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. [6] 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, [7] India, South Africa, Italy, [8] Greece, Spain and, through Spanish influence, the Philippines and many Hispanic American countries.[ citation needed ] In modern times, fewer Spaniards take a daily siesta, ostensibly due to more demanding work schedules. [9]

Historical "first sleep" and "second sleep"

A Historical "First and Second Sleep" Pattern Historical First and Second Sleep.png
A Historical "First and Second Sleep" Pattern

A separate biphasic sleep pattern is sometimes described as segmented sleep, involved sleeping in two phases, separated by about an hour of wakefulness. This pattern was common in preindustrial societies, and it was most common to sleep early ("first sleep"), wake around midnight, and return to bed later ("second sleep"). [10] Along with a nap in the day, it has been argued that this is the natural pattern of human sleep in long winter nights. [11] [12] A case has been made that maintaining such a sleep pattern may be important in regulating stress. [12]

Historian A. Roger Ekirch [13] [14] has argued that before the Industrial Revolution, interrupted sleep was dominant in Western civilization. Ekirch asserts that the intervening period of wakefulness was used to pray [15] and reflect, [16] 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. [14] He draws evidence from more than 500 references to a segmented sleeping pattern in documents from the ancient, medieval, and modern world. [12] Other historians, such as Craig Koslofsky, [17] have endorsed Ekirch's analysis.

Ekirch suggests that it is due to the modern use of electric lighting that most modern humans do not practice interrupted sleep. [18] Some have proposed that a sleep pattern based on the historical biphasic sleep schedule might be beneficial for stress or improve health markers. Ekirch does not advocate for this, stating that the current uninterrupted sleep pattern is the ideal schedule for the modern world. [19]

Experimental schedules

Everyman schedule

Everyman Sleep Pattern Everyman Sleep Schedule.png
Everyman Sleep Pattern

The Everyman schedule involves sleeping 3 hours during the night ("core sleep"), and taking three 20-minute naps during the day. This totals 4 hours of sleep in a 24-hour period. [20]

Uberman schedule

Uberman Sleep Pattern Uberman Sleep Schedule.png
Uberman Sleep Pattern

The Uberman sleep schedule consists of a 30-minute nap every four hours, totaling 3 hours of sleep in a 24-hour period. [20]

Other variations of this sleep pattern involve 8 naps throughout the day, or 20-minute sleep intervals as opposed to 30 minutes.

Dymaxion schedule

Dymaxion Sleep Pattern Dymaxion.svg
Dymaxion Sleep Pattern

Buckminster Fuller described a regimen consisting of 30-minute naps every six hours. The short article about Fuller's nap schedule in Time in 1943, which referred to the schedule as "intermittent sleeping", says that he maintained it for two years, and notes that "he had to quit because his schedule conflicted with that of his business associates, who insisted on sleeping like other men." [21]

This schedule is likely the most extreme type of polyphasic sleep schedule, totaling only two hours of sleep in a 24-hour period. [22]

In extreme situations

In crises and other extreme conditions, people may not be able to achieve the recommended seven to nine hours of sleep per day. [23] Systematic napping may be considered necessary in such situations.

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. [24] 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. [25] Stampi has written about his research in his book Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep (1992). [26] 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. [27] 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 six and seven naps per day. The naps would not be placed equiphasically, instead occurring more densely during night hours. [28]

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). [29]

Similarly, the Canadian Marine pilots in their trainer's handbook report that:

Under extreme circumstances where sleep cannot be achieved continuously, 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. [30]

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. [31]

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. [32]

Physiology

The brain exhibits high levels of the pituitary hormone prolactin during the period of nighttime wakefulness, which may contribute to the feeling of peace that many people associate with it. [33]

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. [11]

Polyphasic sleep can be caused by irregular sleep-wake syndrome, a rare circadian rhythm sleep disorder which is usually caused by neurological abnormality, head injury or dementia. [34] Much more common examples are the sleep of human infants and of many animals. Elderly humans often have disturbed sleep, including polyphasic sleep. [35]

In their 2006 paper "The Nature of Spontaneous Sleep Across Adulthood", [36] 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.

See also

Related Research Articles

<span class="mw-page-title-main">Sleep</span> Naturally recurring resting state of mind and body

Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with the surrounding environment. While sleep differs from wakefulness in terms of the ability to react to stimuli, it still involves active brain patterns, making it more reactive than a coma or disorders of consciousness.

<span class="mw-page-title-main">Circadian rhythm</span> Natural internal process that regulates the sleep-wake cycle

A circadian rhythm, or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism and responds to the environment. Circadian rhythms are regulated by a circadian clock whose primary function is to rhythmically co-ordinate biological processes so they occur at the correct time to maximize the fitness of an individual. Circadian rhythms have been widely observed in animals, plants, fungi and cyanobacteria and there is evidence that they evolved independently in each of these kingdoms of life.

<span class="mw-page-title-main">Delayed sleep phase disorder</span> Chronic sleep disorder

Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is the delaying of a person's circadian rhythm compared to those of societal norms. The disorder affects the timing of biological rhythms including sleep, peak period of alertness, core body temperature, and hormonal cycles. People with this disorder are often called night owls.

<span class="mw-page-title-main">Siesta</span> Short nap taken in the early afternoon

A siesta is a short 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 in warm-weather zones. The "siesta" can refer to the nap itself, or more generally to a period of the day, generally between 2 and 5 p.m. This period is used for sleep, as well as leisure, midday meals, or other activities.

<span class="mw-page-title-main">Sleep cycle</span> Oscillation between the slow-wave and REM phases of sleep

The sleep cycle is an oscillation between the slow-wave and REM (paradoxical) phases of sleep. It is sometimes called the ultradian sleep cycle, sleep–dream cycle, or REM-NREM cycle, to distinguish it from the circadian alternation between sleep and wakefulness. In humans, this cycle takes 70 to 110 minutes. Within the sleep of adults and infants there are cyclic fluctuations between quiet and active sleep. These fluctuations may persist during wakefulness as rest-activity cycles but are less easily discerned.

<span class="mw-page-title-main">Power nap</span> Short sleep

A power nap or cat nap is a short sleep that terminates before deep sleep. A power nap is intended to quickly revitalize the sleeper.

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A microsleep is a sudden temporary episode of sleep or drowsiness which may last for a few seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious. Episodes of microsleep occur when an individual loses and regains awareness after a brief lapse in consciousness, often without warning, or when there are sudden shifts between states of wakefulness and sleep. In behavioural terms, microsleeps may manifest as droopy eyes, slow eyelid-closure, and head nodding. In electrical terms, microsleeps are often classified as a shift in electroencephalography (EEG) during which 4–7 Hz activity replaces the waking 8–13 Hz background rhythm.

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<i>Why We Nap</i> 1992 book edited by Claudio Stampi

Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep is a 1992 book edited by Claudio Stampi, sole proprietor of the Chronobiology Research Institute. It is frequently mentioned by "polyphasic sleepers", as it is one of the few published books about the subject of systematic short napping in extreme situations where consolidated sleep is not possible.

<span class="mw-page-title-main">Circadian rhythm sleep disorder</span> Family of sleep disorders that affect the timing of sleep

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A chronotype is the behavioral manifestation of underlying circadian rhythm's myriad of physical processes. A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period. Eveningness and morningness are the two extremes with most individuals having some flexibility in the timing of their sleep period. However, across development there are changes in the propensity of the sleep period with pre-pubescent children preferring an advanced sleep period, adolescents preferring a delayed sleep period and many elderly preferring an advanced sleep period.

<span class="mw-page-title-main">Sleep deprivation</span> Condition of not having enough sleep

Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary widely in severity. All known animals sleep or exhibit some form of sleep behavior, and the importance of sleep is self-evident for humans, as nearly a third of a person's life is spent sleeping. Sleep deprivation is common as it affects about one-third of the population.

<span class="mw-page-title-main">Nap</span> Short period of sleep during typical waking hours

A nap is a short period of sleep, typically taken during daytime hours as an adjunct to the usual nocturnal sleep period. Naps are most often taken as a response to drowsiness during waking hours. A nap is a form of biphasic or polyphasic sleep, where the latter terms also include longer periods of sleep in addition to one period. For years, scientists have been investigating the benefits of napping, including the 30-minute nap as well as sleep durations of 1–2 hours. Performance across a wide range of cognitive processes has been tested.

Thomas Alvin Wehr is an American psychiatrist, research scientist, and author. He is a scientist emeritus and former chief of the Clinical Psychobiology branch of the National Institute of Mental Health (NIMH).

Irregular sleep–wake rhythm disorder (ISWRD) is a rare form of circadian rhythm sleep disorder. It is characterized by numerous naps throughout the 24-hour period, no main nighttime sleep episode, and irregularity from day to day. Affected individuals have no pattern of when they are awake or asleep, may have poor quality sleep, and often may be very sleepy while they are awake. The total time asleep per 24 hours is normal for the person's age. The disorder is serious—an invisible disability. It can create social, familial, and work problems, making it hard for a person to maintain relationships and responsibilities, and may make a person home-bound and isolated.

<span class="mw-page-title-main">Second wind (sleep)</span> Sleep phenomenon

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<span class="mw-page-title-main">Pilot fatigue</span> Reduced pilot performance from inadequate energy

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<span class="mw-page-title-main">Roger Ekirch</span> American historian (born 1950)

Arthur Roger Ekirch is University Distinguished Professor of history at Virginia Tech in the United States. He was a Guggenheim fellow in 1998.

References

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  2. ↑ Stampi 1992
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  14. 1 2 Ekirch, A. Roger (2005). At Day's Close: Night in Times Past . W. W. Norton. ISBN   978-0-393-34458-5.[ page needed ]
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