Segmented Sleep

Natural Rhythms

25 April 2007. Modified: 26 July 2009. First published at; moved here 17 June 2013.
Moved to, reformatted, with minor updates, 16 June 2013.
Last Modified: 5 March 2015. Site name change, 1 March 2018.
Site name change, 20 February 2019 ⇒, Studies in Time.

In a Psychiatric Times column entitled Broken Sleep May Be Natural Sleep, Walter A. Brown MD presents an overview of "segmented sleep", referring to biphasic sleep or "first sleep, second sleep" — a natural rhythm of sleep consisting of two phases, with a period of quiet non-anxious wakefulness in between. Brown suggests that where a patient is troubled by broken sleep, that patient may find it less disturbing to learn that such a sleep pattern may in fact be more natural, more of an historical norm, shared, for instance, by giraffes, chipmunks, ancestors and many contemporaries.

Trade Paperback
(October 2006)

A. Roger Ekirch PhD, professor of history at Virginia Tech, is the author of At Day's Close: Night in Times Past (Norton: 2005) [see At Day's Close: webcast — 39 min; 6/20/2005]. The book explores nighttime and nocturnal activity in Western society before the advent of the industrial revolution. Three chapters are devoted to an examination of sleep, including "broken" or "segmented sleep", a pattern of first and second sleep described in diaries, letters, and other historical sources, in language "phrased as if the prospect of awakening in the dead of night was perfectly natural".

Ekirch believes that the period of quiet wakefulness between these two sleep phases represented an opportunity for self-reflection and the contemplation of dreams, for example, affording a deeper connection with the psyche and enabling the unconscious an opportunity to reflect on the realities of the day. Other activities were also pursued in the time between sleeps. One might smoke tobacco, engage in sexual activity or social interaction. These are briefly discussed in the webcast, as is Ekirch's parallel discovery of an experiment in which National Institute of Mental Health sleep researcher Thomas A. Wehr MD successfully replicated what Wehr describes as "prehistoric" sleep patterns in a group of 15 male volunteers who, when subjected to daily 14-hour dark periods for four consecutive weeks, developed a pattern of biphasic sleep and exhibited altered hormonal levels (prolactin and melatonin).

Ekirch and Wehr compared notes. Both believe that this biphasic pattern of sleep - and not our current model of uninterrupted sleep - is "the dominent pattern from time immemorial". Ekirch finds that the pervasiveness of the biphasic pattern, which may have been common for hundreds and, he says, probably thousands of years, began to wane as artificial lighting became more prominent in the late 17th century and allowed people later bed times.


  • Broken Sleep May Be Natural Sleep
    Walter A. Brown MD, Psychiatric Times, March 01, 2007 Vol. 24 No. 3
    A version of this column was previously published in Applied Neurology, 26 May 2006.
    See Acknowledging Preindustrial Patterns of Sleep May Revolutionize Approach to Sleep Dysfunction.
  • Sleep Disorder? Wake Up and Smell the Savanna,
    Richard A. Friedman MD, The New York Times, 14 March 2006

    It's a question that Dr. Thomas Wehr at the National Institute of Mental Health asked himself in the early 1990's. He conducted a landmark experiment in which he placed a group of normal volunteers in 14-hour dark periods each day for a month. He let the subjects sleep as much and as long as they wanted during the experiment.

    The first night, the subjects slept an average of 11 hours a night, probably repaying a chronic sleep debt.

    By the fourth week, the subjects slept an average of eight hours a night — but not consecutively. Instead, sleep seemed to be concentrated in two blocks. First, subjects tended to lie awake for one to two hours and then fall quickly asleep. Dr. Wehr found that the abrupt onset of sleep was linked to a spike in the hormone melatonin. Melatonin secretion by the brain's pineal gland is switched on by darkness.

    After an average of three to five hours of solid sleep, the subjects would awaken and spend an hour or two of peaceful wakefulness before a second three- to five-hour sleep period. Such bimodal sleep has been observed in many other animals and also in humans who live in pre-industrial societies lacking artificial light.

    Carol Worthman, an anthropologist at Emory University in Atlanta, has studied the sleep patterns of non-Western populations. From the !Kung hunter-gatherers in Africa to the Swat Pathan herders in Pakistan, Dr. Worthman documented a pattern of communal sleep in which individuals drifted in and out of sleep throughout the night.

    She speculates that there may even be an evolutionary advantage to interrupted sleep. "When we lived in open exposed savanna, being solidly asleep leaves us vulnerable to predators."

  • Dreams Deferred,
    A. Roger Ekirch, The New York Times, 19 February 2006

    Until the modern age, most households had two distinct intervals of slumber, known as "first" and "second" sleep, bridged by an hour or more of quiet wakefulness. Usually, people would retire between 9 and 10 o'clock only to stir past midnight to smoke a pipe, brew a tub of ale or even converse with a neighbor.

    Others remained in bed to pray or make love. This time after the first sleep was praised as uniquely suited for sexual intimacy; rested couples have "more enjoyment" and "do it better," as one 16th-century French doctor wrote. Often, people might simply have lain in bed ruminating on the meaning of a fresh dream, thereby permitting the conscious mind a window onto the human psyche that remains shuttered for those in the modern day too quick to awake and arise.

  • Sleep We Have Lost: Pre-industrial Slumber in the British Isles,
    A. Roger Ekirch, The American Historical Review, April 2001 (52 pars.)

    Perhaps even more commonly, however, people used this shrouded interval of solitude to immerse themselves in contemplation — to ponder events of the preceding day and to prepare for the arrival of dawn. At no other time, during the day or night, were distractions so few and privacy so great. "The night," asserted James Pilkington, "is the quietest time to devise things in"; the "eyes are not troubled with looking at many things," and the "senses are not drawn away."93 Naturally, midnight reflections sometimes proved painful. A character in the Jacobean comedy Everie Woman in Her Humor "everie night after his first sleepe" wrote "lovesicke sonnets, rayling against left handed fortune his foe."94 Little wonder that, for better or worse, nighttime enjoyed a far-flung reputation as the "mother of thoughtes," many of them born while minds were conscious. "The night brings counsel," echoed a popular proverb.95 The seventeenth-century merchant James Bovey reputedly from age fourteen kept a "Candle burning by him all night, with pen, inke, and paper, to write downe thoughts as they came into his head." Indeed, by the mid-eighteenth century, in order to better preserve midnight ruminations, methods were devised to "write in the dark, as straight as by day or candle-light," according to a report in 1748. Twenty years later, after first obtaining a patent, a London tradesman, Christopher Pinchbeck, Jr., advertised his "Nocturnal Remembrancer," an enclosed tablet of parchment with a horizontal aperture for a guideline whereby "philosophers, statesmen, poets, divines, and every person of genius, business or reflection, may secure all those happy, often much regretted, and never to be recovered flights or thoughts, which so frequently occur in the course of a meditating, wakeful night."

    Often, people stirred from their first sleep to ponder a kaleidoscope of partially crystallized images, slightly blurred but otherwise vivid tableaus born of their dreams. So in the "Squire's Tale," "Canacee," after she "slept her first sleep," awakened in the warm glow of a dream — "for on her heart so great a gladness broke"; and "Club," when awakened from his "first sleep" in Love and a Bottle, recalled the "pleasantest Dream" in which "his Master's great black Stone-horse, had broke loose among the Mares." Less happily, Reverend Oliver Heywood — "at my first sleep" — had a "terrible dream" in which his son "was fallen to the study of magick or the black art." And in Ram Alley, "Sir Oliver" spoke of the hours before cockcrow "when maids awak'd from their first sleep, Deceiv'd with dreams begin to weep."

  • Night life: In the pre-industrial age, night was a time for reflection,
    and for an entirely different way of life than the day demanded
    Sally Harris, Research Magazine, Virginia Tech, 1999
  • Familial advanced sleep-phase syndrome:
    A short-period circadian rhythm variant in humans
    Christopher R. Jones, et al.
    Nature Medicine, Vol.5, No.9, September 1999
  • Modern Life Suppresses An Ancient Body Rhythm,
    Natalie Angier, The New York Times, 14 March 1995
  • Extended sleep in humans in 14 hour nights (LD 10:14):
    relationship between REM density and spontaneous awakening.
    G. Barbato, C. Barker, C. Bender, H.A. Giesen, T.A. Wehr.
    Electroencephalogr Clin Neurophysiol. 1994 Apr;90(4):291-7.
  • Conservation of photoperiod-responsive mechanisms in humans,
    T. A. Wehr, D. E. Moul, G. Barbato, H. A. Giesen, J. A. Seidel, C. Barker, C. Bender.
    Am J Physiol Regul Integr Comp Physiol 265:R846-R857, 1993;0363-6119/93
  • In short photoperiods, human sleep is biphasic.,
    Thomas A. Wehr, J Sleep Res. 1992 Jun;1(2):103-107

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