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 behaviour 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]

Historical use

Six hours sleep and a mid day siesta Biphasic.svg
Six hours sleep and a mid day 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. 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, [6] India, South Africa, Italy, [7] Greece, Spain and, through Spanish influence, the Philippines and many Hispanic American countries.[ citation needed ]

A separate biphasic sleep pattern is sometimes described as segmented sleep, often consisting of going to sleep early at night, awakening in the post-midnight hours, and then returning to bed for a second period of sleep into the morning. In a New York Times article, author Jesse Barron asserts that this practice was common in the past: "in the preindustrial West, most people slept in two discrete blocks." [8] Benjamin Franklin was a prominent example of this sleeping pattern. [8] Interrupted sleep is a primarily biphasic sleep pattern where two periods of nighttime sleep are punctuated by a period of wakefulness. Along with a nap in the day, it has been argued that this is the natural pattern of human sleep in long winter nights. [9] [10] A case has been made that maintaining such a sleep pattern may be important in regulating stress. [10]

A belief in the need for biphasic sleeping as essential to the health of children is mentioned in a letter in the seminal nineteenth-century text Street Music in the Metropolis: Correspondence and Observations on the Existing Law, and Proposed Amendments: "With children to whom it is essential that they should have sleep twice a day, being very young, street music is a great nuisance." [11]

Sleep pattern described by Buckminster Fuller: Thirty minutes nap every six hours Dymaxion.svg
Sleep pattern described by Buckminster Fuller: Thirty minutes nap every six hours

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." [12]

Ekirch's analysis of biphasic sleep in the pre-industrial era

Historian A. Roger Ekirch [13] [14] 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. [10] Other historians, such as Craig Koslofsky, [15] 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. [14] This time was used to pray [16] and reflect, [17] and to interpret dreams, which were more vivid at that hour than upon waking in the morning. This was also a favourite time for scholars and poets to write uninterrupted, whereas still others visited neighbours, engaged in sexual activity, or committed petty crime. [14] : 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. [18] Superimposed on this basic rhythm is a secondary one of light sleep in the early afternoon. 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. [19]

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. [14] : 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 17th century, but according to Ekirch, was commonly mistranslated in the 20th. [14] : 303 

Ekirch's research into the commonality of biphasic sleep in the preindustrial West has led some to conclude he believes that the human body has a "natural preference for segmented sleep." [10] However, when directly asked if he espoused the idea that biphasic sleep was preferable, he responded "Not at all.  At no time in history have conditions for human slumber been better than today. If the purpose of sleep is mental and physical well-being, there is very good reason to believe that uninterrupted sleep at night best achieves that outcome." [20]

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. [21] 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. [22] 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. [23] Stampi has written about his research in his book Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep (1992). [24] 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. [25] 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. [26]

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). [27]

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.

—  [28]

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. [29]

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. [30]

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. [19]

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. [9]

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. [31] Much more common examples are the sleep of human infants and of many animals. Elderly humans often have disturbed sleep, including polyphasic sleep. [32]

In their 2006 paper "The Nature of Spontaneous Sleep Across Adulthood", [33] 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

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<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 maximise 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 mismatch between a persons normal daily rhythm, compared to other people and societal norms

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.

<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 2–5 p.m. This period is used for sleep, as well as leisure, mid-day meals, or other activities.

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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.

Circadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep-wake disorders (CRSWD), are a family of sleep disorders which affect the timing of sleep. CRSDs arise from a persistent pattern of sleep/wake disturbances that can be caused either by dysfunction in one's biological clock system, or by misalignment between one's endogenous oscillator and externally imposed cues. As a result of this mismatch, those affected by circadian rhythm sleep disorders have a tendency to fall asleep at unconventional time points in the day. These occurrences often lead to recurring instances of disturbed rest, where individuals affected by the disorder are unable to go to sleep and awaken at "normal" times for work, school, and other social obligations. Delayed sleep phase disorder, advanced sleep phase disorder, non-24-hour sleep–wake disorder and irregular sleep–wake rhythm disorder represents the four main types of CRSD.

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

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References

  1. ↑ Morin, Charles M.; Espie, Colin A. (2012). The Oxford Handbook of Sleep and Sleep Disorders. Oxford University Press, USA. p. 224. ISBN   978-0-19-537620-3.
  2. ↑ Stampi 1992
  3. ↑ Capellini, I.; Nunn, C. L.; McNamara, P.; Preston, B. T.; Barton, R. A. (1 October 2008). "Energetic constraints, not predation, influence the evolution of sleep patterning in mammals". Functional Ecology. 22 (5): 847–853. doi:10.1111/j.1365-2435.2008.01449.x. PMC   2860325 . PMID   20428321.
  4. ↑ "People Are Sleeping in 20-Minute Bursts To Boost Productivity". Time. 30 January 2018. Retrieved 10 August 2023.
  5. ↑ Weaver, Matthew D.; Sletten, Tracey L.; Foster, Russell G.; Gozal, David; Klerman, Elizabeth B.; Rajaratnam, Shantha M. W.; Roenneberg, Till; Takahashi, Joseph S.; Turek, Fred W.; Vitiello, Michael V.; Young, Michael W.; Czeisler, Charles A. (June 2021). "Adverse impact of polyphasic sleep patterns in humans: Report of the National Sleep Foundation sleep timing and variability consensus panel". Sleep Health. 7 (3): 293–302. doi: 10.1016/j.sleh.2021.02.009 . ISSN   2352-7226. PMID   33795195.
  6. ↑ "Napping Around the World". Sleep.org. 21 December 2017. Retrieved 28 May 2019. In China: Workers often take a break after lunch and put their heads on their desks for an hour-long nap. It's considered a Constitutional right.
  7. ↑ Finzi, Jerry (23 May 2016). ""Chiuso" means Closed in Italy: The Midday Riposa (Siesta), The Italian Siesta". GRAND VOYAGE ITALY. Retrieved 28 May 2019.
  8. 1 2 Barron, Jesse (31 March 2016). "Letter of Recommendation: Segmented Sleep". The New York Times Magazine . Retrieved 16 May 2021.
  9. 1 2 Wehr, T. A. (June 1992). "In short photoperiods, human sleep is biphasic". Journal of Sleep Research. 1 (2): 103–107. doi:10.1111/j.1365-2869.1992.tb00019.x. PMID   10607034.
  10. 1 2 3 4 Hegarty, Stephanie (22 February 2012). "The myth of the eight-hour sleep". BBC News .
  11. ↑ Bass, Michael Thomas (1864). Street music in the metropolis. Oxford University. London: London, J. Murray. p. 25 – via Archive.org.
  12. ↑ "Science: Dymaxion Sleep". Time . 11 October 1943. Archived from the original on 2 March 2016.
  13. ↑ Ekirch, A. Roger (2001). "Sleep We Have Lost: Pre-industrial Slumber in the British Isles". The American Historical Review . 106 (2): 343–386. doi:10.2307/2651611. JSTOR   2651611. PMID   18680884.
  14. 1 2 3 4 5 Ekirch, A. Roger (2005). At Day's Close: Night in Times Past . W. W. Norton. ISBN   978-0-393-34458-5.[ page needed ]
  15. ↑ Koslofsky, C. M. (2011). "An early modern revolution". Evening's Empire: A History of the Night in Early Modern Europe. pp. 1–18. doi:10.1017/CBO9780511977695.001. ISBN   9780511977695.
  16. ↑ Hinds, William Alfred (1908). American Communities and Co-operative Colonies p 22 at the Internet Archive. "the followers of Beissel were wont to assemble for prayer and worship at midnight, the services lasting till one o'clock, when a second period of sleep till four was allowed."
  17. ↑ Frances Quarles (London 1644), Enchirdion ch. 54
  18. ↑ Gamble, Jessa (2010). Our natural sleep cycle. TEDGlobal 2010, Oxford, England (video). TED Conferences, LLC. Retrieved 27 April 2014. In today's world, balancing school, work, kids and more, most of us can only hope for the recommended eight hours of sleep. Examining the science behind our body's internal clock, Jessa Gamble reveals the surprising and substantial program of rest we should be observing.
  19. 1 2 Randall, David K. (2012). "2. Light My Fire". Dreamland: Adventures in the Strange Science of Sleep. W. W. Norton. pp. 17–18. ISBN   978-0-393-08393-4.
  20. ↑ Thompson, Derek (27 January 2022). "Can Medieval Sleeping Habits Fix America's Insomnia?". The Atlantic. Retrieved 5 October 2023.
  21. ↑ Watson, Nathaniel F.; Badr, M. Safwan; Belenky, Gregory; Bliwise, Donald L.; Buxton, Orfeu M.; Buysse, Daniel; Dinges, David F.; Gangwisch, James; Grandner, Michael A.; Kushida, Clete; Malhotra, Raman K.; Martin, Jennifer L.; Patel, Sanjay R.; Quan, Stuart F.; Tasali, Esra (1 June 2015). "Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society". Sleep. 38 (6): 843–844. doi:10.5665/sleep.4716. ISSN   0161-8105. PMC   4434546 . PMID   26039963.
  22. ↑ Wanjek, Christopher (18 December 2007). "Can You Cheat Sleep? Only in Your Dreams". LiveScience.
  23. ↑ "Catching catnaps, on season 1, episode 5". Scientific American Frontiers . Chedd-Angier Production Company. 1990–1991. PBS. Archived from the original on 1 January 2006.
  24. ↑ Stampi, Claudio, ed. (2013). Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep. Springer Science & Business Media. doi:10.1007/978-1-4757-2210-9. ISBN   978-1-4757-2210-9.[ page needed ]
  25. ↑ Stampi, Claudio (January 1989). "Polyphasic sleep strategies improve prolonged sustained performance: A field study on 99 sailors". Work & Stress . 3 (1): 41–55. doi:10.1080/02678378908256879.
  26. ↑ Stampi, Claudio (12 June 2004). "Rich Wilson's Sleep Patterns Prior to and During the Transat Race". Chronobiology Research Institute, Boston, Massachusetts.
  27. ↑ Caldwell, John A. (February 2003). An Overview of the Utility of Stimulants as a Fatigue Countermeasure for Aviators (PDF). Brooks AFB, Texas: United States Air Force Research Laboratory. p. 15. Archived from the original on 25 August 2016.
  28. ↑ Rhodes, Wayne; Gil, Valérie (17 January 2007). Fatigue Management Guide for Canadian Marine Pilots – A Trainer's Handbook (TP 13960E). Transport Canada, Transportation Development Centre. Minimum Sleep Requirement. Archived from the original on 28 December 2013.
  29. ↑ "NASA-supported sleep researchers are learning new and surprising things about naps". NASA Science: Science News. NASA. 3 June 2005.
  30. ↑ Porcu, S.; Casagrande, M.; Ferrara, M.; Bellatreccia, A. (July 1998). "Sleep and Alertness During Alternating Monophasic and Polyphasic Rest-Activity Cycles". International Journal of Neuroscience. 95 (1–2): 43–50. doi:10.3109/00207459809000648. PMID   9845015.
  31. ↑ Zee, Phyllis C.; Michael V. Vitiello (June 2009). "Circadian Rhythm Sleep Disorder: Irregular Sleep Wake Rhythm Type". Sleep Med Clin. 4 (2): 213–218. doi:10.1016/j.jsmc.2009.01.009. PMC   2768129 . PMID   20160950.
  32. ↑ Mori, A. (January 1990). "Sleep disturbance in the elderly". Nippon Ronen Igakkai Zasshi (Abstract in English). 27 (1): 12–7. doi: 10.3143/geriatrics.27.12 . PMID   2191161.
  33. ↑ Campbell, Scott S.; Murphy, Patricia J. (March 2007). "The nature of spontaneous sleep across adulthood". Journal of Sleep Research. 16 (1): 24–32. doi:10.1111/j.1365-2869.2007.00567.x. PMID   17309760.

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