Segmented sleep

Segmented sleep, also known as divided sleep, bimodal sleep pattern, or interrupted sleep, is a polyphasic or biphasic sleep pattern where two or more periods of sleep are punctuated by a period of wakefulness.

A. Roger Ekirch, a historian at Virginia Tech, found that a wide variety of early documents in modern non-industrialised societies, medieval, and early modern Europe discuss about the practice of segmented sleep. Segmented sleep is also particularly common in the winter.^[1] The Pirahã people of the Amazon take naps of 15 minutes to, at the most, two hours throughout the day and night and rarely sleep through the night ^[2].

This period of wakefulness was often only semi-conscious, as the French term dorveille implies (see Etymology). It was highly valued in medieval Europe as a time of quiet and relaxation. Peasant couples were often too tired after a long day's work to do much more than eat and go to sleep, but they would wake later on to talk and have sex.^[3] People would also use this time to pray and reflect,^[4] and to interpret dreams, which were more vivid at that hour than upon waking in the morning,^[5] and even to visit. This was also a favorite time for scholars and poets to write uninterrupted.

The human circadian rhythm regulates the human sleep-wake cycle of wakefulness during the day and sleep at night. Due to the modern use of electric lighting, most modern humans do not practice segmented sleep, which is a concern for some scientists.^[6] Superimposed on this basic rhythm is a secondary one of light sleep in the early afternoon (see siesta) and quiet wakefulness in the early morning.

There is evidence from sleep research that this period of nighttime wakefulness, combined with a midday nap, results in greater alertness than a monophasic sleep-wake cycle.^{[citation needed]} 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. It is in many ways similar to the hypnogogic and hypnopompic states which occur just before falling asleep and upon waking, respectively.

The modern assumption that consolidated sleep with no awakenings is the normal and correct way for human adults to sleep, may lead many people to approach their doctors with complaints of maintenance insomnia or other sleep disorders.  Their concerns might best be addressed by assurance that their sleep conforms to historically natural sleep patterns.^[7]

Etymology

The two periods of night sleep were called "first sleep" (occasionally "dead sleep") and "second sleep" (or "morning sleep") in medieval England. First and second sleep are also the terms in the Romance languages, as well as the Tiv of Nigeria: In French, the common term was premier sommeil or premier somme; in Italian, primo sonno; in Latin, primo somno or comcubia nocte.^[8] There is 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 French an equivalent generic term is dorveille ("twixt sleep and wake").

Because members of modern industrialised societies, with late hours facilitated by electric lighting, mostly do not practice segmented sleep, they may misinterpret and mistranslate references to it in literature. Common interpretations of the term "first sleep" are "beauty sleep" and "early slumber". A reference to first sleep in the Odyssey was translated as such in the 17th century, but universally mistranslated in the 20th.^[9]

See also

• Polyphasic sleep
• Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep (book)
• Siesta
• Circadian rhythm
• Sleep

References

1. ^ Coturnix (16 October 2006). "What is a 'natural' sleep pattern?". A Blog Around the Clock (ScienceBlogs). http://scienceblogs.com/clock/2006/10/what_is_a_natural_sleep_patter.php. Retrieved 2007-12-29. "Includes image: the original data from Wehr's experiment." 
2. ^ Everett 2008 pp. xvii, 13, 70, 79
3. ^ A. Roger Ekirch (2005), At Day's Close: Night In Times Past, pp. 308-310 ISBN 0-393-05089-0
4. ^ Frances Quarles (London 1644), Enchirdion ch. 54
5. ^ A. Roger Ekirch (2005), At Day's Close: Night In Times Past, pp. 311-323 ISBN 0-393-05089-0
6. ^ "Jessa Gamble: Our natural sleep cycle | Video on". Ted.com. http://www.ted.com/talks/jessa_gamble_how_to_sleep.html. Retrieved 2011-03-22. 
7. ^ Brown, Walter A., MD (2006-05-26). "Acknowledging Preindustrial Patterns of Sleep May Revolutionize Approach to Sleep Dysfunction". Applied Neurology (CMPMedica). http://appneurology.com/showArticle.jhtml?articleId=188500785. Retrieved 2008-02-03. "The discoveries of Ekirch and Wehr raise the possibility that segmented sleep is "normal" and, as such, these revelations hold significant implications for both understanding sleep and the treatment of insomnia." 
8. ^ A. Roger Ekirch (2005), At Day's Close: Night In Times Past, pp. 301-302 ISBN 0-393-05089-0
9. ^ A. Roger Ekirch (2005), At Day's Close: Night In Times Past, p. 303 ISBN 0-393-05089-0

Further reading

• Everett, Daniel L. (2008) Don't Sleep, there are Snakes, Pantheon Books ISBN 978-0-375-42502-8
• Warren, Jeff (2007). "The Watch". The Head Trip: Adventures on the Wheel of Consciousness. Toronto: Random House Canada. ISBN 978-0679314080. 
• Jean Verdon, Night in the Middle Ages, trans. George Holoch (2002). ISBN 026803656X.

External links

• Sleep We Have Lost: Pre-industrial Slumber in the British Isles
• Library of Congress Webcast - At Day's Close: Night In Times Past
• Slumber's Unexplored Landscape: People in traditional societies sleep in eye-opening ways
• New York Times, Richard A. Friedman, M.D., March 14, 2006, Wake Up and Smell the Savanna
• Coturnix, ScienceBlogs Includes image of original data, Wehr's experiment
• The science of sleep: Jessa Gamble on TED.com