||It has been suggested that this article be merged with Polyphasic sleep. (Discuss) Proposed since June 2015.|
Segmented sleep, also known as divided sleep, bimodal sleep pattern, bifurcated sleep, or 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 (siesta) 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, segmented sleep was dominant in Western civilization. He draws evidence from documents from the ancient, medieval, and modern world. Other historians, such as Craig Koslofsky, have endorsed Ekirch's analysis.
As a historical norm
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 sex, 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 segmented 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 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. 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 segmented 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 eight 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 had. 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.
In Dreamland: Adventures in the Strange Science of Sleep, David K. Randall discusses how during the nocturnal waking period of a segmented sleep the hormone prolactin is released, along with other physiological changes. Prolactin is released with the relaxation that accompanies orgasm.
- Wehr, T. A. (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.
- Hegarty, Stephanie (22 February 2012). "The myth of the eight-hour sleep". BBC News.
- Ekirch, A. Roger (2001). "Sleep We Have Lost: Pre-industrial Slumber in the British Isles" (PDF). The American Historical Review (Oxford University Press on behalf of the American Historical Association) 106 (2): 343–386. doi:10.2307/2651611. JSTOR 2651611. PMID 18680884.
- A. Roger Ekirch (2005), At Day's Close: Night In Times Past ISBN 0-393-05089-0
- Koslofsky, C. M. (2011). "An early modern revolution". Evening's Empire: A History of the Night in Early Modern Europe. p. 1. doi:10.1017/CBO9780511977695.001. ISBN 9780511977695.
- A. Roger Ekirch (2006), At Day's Close: Night In Times Past, New York: Norton, pp. 308–310 ISBN 0-393-05089-0
- Frances Quarles (London 1644), Enchirdion ch. 54
- Ekirch, A. Roger (2005). At Day's Close: Night In Times Past. Phoenix. ISBN 0-393-05089-0.
- Gamble, Jessa (2010). Our natural sleep cycle (video). TEDGlobal 2010, Oxford, England: TED Conferences, LLC. Retrieved 2014-04-27.
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.
- David K. Randall (13 August 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. Retrieved 3 August 2014.
- Brown, Walter A., MD (2006-05-26). "Acknowledging Preindustrial Patterns of Sleep May Revolutionize Approach to Sleep Dysfunction". Applied Neurology (CMPMedica). 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.
- Wehr TA (1992). "In short photoperiods, human sleep is biphasic.". PMID 10607034. This site summarizes the study: http://www.psychiatrictimes.com/sleep-disorders/acknowledging-preindustrial-patterns-sleep-may-revolutionize-approach-sleep-dysfunction
- Exton MS, Krüger TH, Koch M, et al. (April 2001). "Coitus-induced orgasm stimulates prolactin secretion in healthy subjects". Psychoneuroendocrinology 26 (3): 287–94. doi:10.1016/S0306-4530(00)00053-6. PMID 11166491.
- Ekirch, A. Roger (2006) At Day's Close: Night in Times Past, W.W. Norton ISBN 978-0393329018
- Everett, Daniel L. (2008) Don't Sleep, there are Snakes, Pantheon Books ISBN 978-0-375-42502-8
- Koslofsky, Craig (2011) Evening's Empire: A History of the Night in Early Modern Europe.
- Verdon, Jean, Night in the Middle Ages, trans. George Holoch (2002). ISBN 0-268-03656-X.
- Warren, Jeff (2007). "The Watch". The Head Trip: Adventures on the Wheel of Consciousness. Toronto: Random House Canada. ISBN 978-0-679-31408-0.
- 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
- Decoding the Science of Sleep