segmented sleep

_58434887_jan_saenredamA 1595 engraving by Jan Saenredam. historical evidence of human activity at night


The other day I heard an odd reference on the radio which sent me to the Internet, where I made a surprising discovery. Uninterrupted eight-hour sleep is a creation of the Industrial Revolution and that period’s changeover to mechanical time. It is unnatural and, possibly, unhealthy. And a boon to “sleep therapists” who try to reinforce an inherently artificial practice.

The natural pattern of sleep—the way our ancestors passed the time in darkness—is to sleep first for four hours, then wake for one or two hours before falling into a second four-hour sleep.

The scientists call this natural pattern “segmented sleep”, “divided sleep”, “bimodal sleep pattern”, “bifurcated sleep”, or “interrupted sleep”—a polyphasic or biphasic sleep pattern where two or more periods of sleep are punctuated by periods of wakefulness. Along with a nap (siesta) in the day, it has been argued that this is the natural pattern of human sleep. A case has been made that maintaining such a sleep pattern may be important in regulating stress.

I have been sleeping by this pattern for years, doing what came naturally to me—but I just thought I was weird. Now, it seems, I have simply been following the pattern that human beings had been practicing for thousands of years, before the first 18th century factory owners and Thomas Edison.

In the early 1990s, psychiatrist Thomas Wehr conducted an experiment in which a group of people were plunged into darkness for 14 hours every day for a month. It took some time for their sleep to regulate but by the fourth week the subjects had settled into a very distinct sleeping pattern. They slept first for four hours, then woke for one or two hours before falling into a second four-hour sleep.

Though sleep scientists were impressed by the study, among the general public the idea that we must sleep for eight consecutive hours persists.

In 2001, historian Roger Ekirch of Virginia Tech published a seminal paper, drawn from 16 years of research, revealing a wealth of historical evidence that humans used to sleep in two distinct chunks.

His book At Day’s Close: Night in Times Past, published four years later, unearths more than 500 references to a segmented sleeping pattern—in diaries, court records, medical books and literature, from Homer’s Odyssey to an anthropological account of modern tribes in Nigeria.

During this waking period people were quite active. They often got up, went to the toilet, smoked tobacco, tended fireplace fires or campfires, and some even visited neighbors. Most people stayed in bed, read, wrote and often prayed. Countless prayer manuals from the late 15th Century offered special prayers for the hours in between sleeps.

And these hours weren’t entirely solitary—people often chatted to bed-fellows or had sex. A doctor’s manual from 16th Century France even advised couples that the best time to conceive was not at the end of a long day’s labor but “after the first sleep”, when “they have more enjoyment” and “do it better”.

Ekirch found that references to the first and second sleep started to disappear during the late 17th Century. This started among the urban upper classes in northern Europe and over the course of the next 200 years filtered down to the rest of Western society. By the 1920s the idea of a first and second sleep had receded entirely from our social consciousness.

He attributes the initial shift to improvements in street lighting, domestic lighting and a surge in coffee houses—which were sometimes open all night. Before the 17th century the night was a place populated by people of disrepute—criminals, prostitutes and drunks. As the night became a place for legitimate activity and as that activity increased, the length of time people could dedicate to rest dwindled.

A long time ago, I learned not to fret about my nocturnal habits, but to use the hours most productively. Twenty-five years ago I devoted this time between sleeps to walking with my best friend along the rail lines that would eventually become biking and pedestrian trails in Minneapolis. Now I devote the time to writing or thinking about the subjects for my next days’ blog posts.

For me, this is the most creative time of the day when my thoughts are uninterrupted by the normal distractions of the day. For me, these are my happiest hours when I am free to be me.


Groove of the Day

Listen to The Shins performing “Sleeping Lessons”


1 Response to “segmented sleep”

  1. November 6, 2014 at 1:13 pm

    But, just because we used to do things in a certain way while living in caves does not make it “natural”. As you say for the 8-hour pattern, being the product of our age, so was that 4-2-4 back then. With all the dangers and necessity to get food, perhaps sleeping for 8 hours was deadly? And that experiment is weird. If you put me in a dark room, with nothing to do, at some point I will surely fall asleep. It may not be a product of a natural sleep cycle, but a product of our bodies being programmed to use idle time to rest. I would also force myself to sleep, to make time “fly by”. If awake, wouldn’t you go mad being in dark for 14 hours? I’ve quit my job almost 4 years ago and can basically afford any sleeping pattern. Not limited by working hours or anything. Still, my pattern remained the same. Why did I not revert? I don’t drink coffee, nor any soda drinks. No, no drugs, either. 🙂

    Also, the last (and only) time I napped in the afternoon, I woke up miserable, like being beaten the whole time. And if awaken after just 4 hours, I’d be a wreck and wouldn’t recover after 4 more. “It takes time to get used”, but I don’t see anything in that study to make me think the habit of another pattern would make me feel better. I think of “natural” as something that our body chemistry reacts to, not just as of a matter of habit. For example, the growth hormone (I believe :)) is created and released around midnight and that makes it “natural” to be asleep at that time. So, kids are “naturally programmed” to go to sleep before 23 h. Some also say teenagers should not start school before 9 am, due to some chemistry.. thing. But sleeping _pattern_ seems to be individual (though usually forced upon us by the lifestyle). And couldn’t it be that the electric lighting simply enabled us to realize and utilize our full potential? Far beyond the caveman.

    Hm.. this could also be interesting – which extreme makes us sleep more – boredom or exhaustion? Perhaps Alex could provide some insight? When in solitary confinment, with absolutely nothing to do all day long, would you say you slept more, less or the same, during a 24 hour period, compared to a “normal” day? I know you did not have a watch, just asking for.. an educated guess.

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