Biphasic sleep

We have got used to thinking that a proper night’s sleep consists of somewhere between seven and nine hours at a stretch during the night. Hence people who get up in the middle of the night and find it hard to get back to sleep immediately may fret that they are insomniacs. But not that long ago, before the invention of street lights that allowed people in urban areas to go out and about long after sunset, people would go to sleep an hour or so after sunset, get up after a few hours and do other things, and then go back to sleep. Such a two-sleep pattern was called biphasic sleep.

“During the industrial revolution, when the sun went down, there was no electricity so people had to sleep,” [neurologist Dr. Pedram] Navab said. “And then they kind of woke up for the second time, [known as] the second sleep and they journaled or whatnot.” 

Historian Roger Ekirch looked back at prayer manuals from the late 15th century, which offered specific prayers for the time in between sleeps. A doctor’s manual from the 16th century advised couples to conceive “after the first sleep.” “Families rose to urinate, smoke tobacco, and even visit close neighbors,” Ekirch wrote in his book, “At Day’s Close: Night in Times Past.” “Many others made love, prayed, and most important historically, reflected on their dreams, a significant source of solace and self-awareness.” 

Navab said typically the first sleep began two hours after dusk. People woke up for an hour or two — after four to six hours of sleep — and then went back to sleep until dawn. 

But by the 1920s, the idea of two sleep sessions, and enjoying what happened in between, began to fade.

These researchers try to reassure people who worry about what they consider disrupted sleep, that it might be a sign of deeper problems, that it may not be that serious.

From a medical standpoint, Navab said there isn’t an issue with segmented sleep. 

“I don’t think that’s an issue as long as you’re able to go back to sleep and get sufficient hours of sleep,” Navab said. “As long as they’re waking up when the sun is coming back up, I think that’s really the most important thing, and they’re going to bed when it’s night, those are really the most important things.”

In fact, Ekirch has argued that this is the more natural way to sleep. 

“My argument has been, and this has been backed up by some prominent sleep scientists, that one reason why some people do suffer from what has been termed middle of the night insomnia is that many of these cases, these individuals are experiencing a powerful remnant or echo of this long, dominant pattern of biphasic sleep,” Ekirch said. “I’ve been told over and over again that it eases the anxiety of individuals who suffer from insomnia.”

I have a friend who was worried about just such a thing and was indeed reassured by knowing that there may be benign reasons for it.


  1. Matt G says

    I kinda lump sleep science in with nutrition and exercise science. So many variables, and so much individual variation. It also makes me think of evolutionary psychology and what appear to be just-so stories.

  2. lochaber says

    Marcus Ranum@1>

    capitalism already killed the siesta. HR will mandate a few training vids, there will be some talk from managers about hydration, and then the hourlies will have to sign some form stating that they’ve been informed of, and understand the risks of heat injuries, and how to avoid them, and if they succumb to heat exhaustion/illness/stroke, it’s due to their own neglect, and they will now be responsible for reimbursing the corporation for expenses accrued whilst they were neglecting job duties…

    I mean, we haven’t forgotten the stories about ambulances pre-emptively staging outside amazon warehouses during the summer, right?

  3. Jazzlet says

    Matt G @2

    Sleep science, nutrition science and exercise science are just that, as rigorous as any other branch of science. The problem in all three cases is that there are a lot of people trying to make money by citing basic studies to support their “clinical ” practise when the the work simply hasn’t been done or has been done and has overturned whatever treatment they like to charge for. And that’s not even getting into the people setting themselves up as experts without any reference to the science at all. Whereas evolutionary psychology has no scientific basis at all and is indeed a bunch of just-so stories.

  4. mnb0 says

    There is also a thing called siesta -- very handy in tropical countries like Suriname. It’s correct that people need 7 -- 9 hours sleep a day (though now I’m approaching 60 it tends to be slightly less than 7 for me), but it doesn’t matter that much how you divide it.

  5. ionopachys says

    This idea has been around for quite some time, but the last I read this sleep pattern is not seen throughout the world. Anthropologist looking into it have found that most Africans sleep through the night, and presumably always have. If biphasic sleep was a consistent, culture-wide behavior based in biology, at best it was an adaptation to long winter nights that many Americans would not possess. At worst, to paraphrase a critic, it could be that Europeans developed a pathological sleep pattern.

  6. says

    I tend towards a crepuscular lifestyle, when left to my own devices. Active around dawn and dusk, largely asleep or “resting” the rest of the time. The only reason I’m up during daylight hours is because society doesn’t do well accommodating anyone who isn’t a firm wake-with-the-sun Daytime! person.

  7. moarscienceplz says

    I think this whole idea is junk science. The author(s) seem to have forgotten that humans have had artificial light for thousands of years. Have they never heard of candles, oil lamps, or fireplaces?
    The phrase “in the limelight” refers to nighttime entertainment that was put on well before electric lights existed when it was found that pieces of quicklime (calcium oxide) gave off a bright white light when heated by a gas flame.
    Taverns and pubs were invented as a way to share the cost of artificial light among the whole village: one fire in the fireplace and a few lamps or candles could be shared by everyone so they all could enjoy the evening and not all go to their individual homes and be in darkness for 12 hours because candles were expensive.
    Why would people have done these things if they really wanted to sleep in the evening?

  8. Jazzlet says

    @ moarscienceplz
    So you’re saying that all of the records we have of people having biphasic sleep are fakes? And that every person in every town and vilage spent all their evenings in the pub?

  9. anat says

    While humans in general tend to sleep 7-9 hours, I can’t bring myself to sleep more than 6 hours no matter what I do. And my spouse knows someone who sleeps less than 4 hours. That person spends half the night walking the streets .

    Many years ago spouse attempted a biphasic sleep regimen as a means to increase productivity. The attempt ended miserably within a few days with spouse becoming very ill. Spouse hasn’t had any coffee since (still drinks yerba mate or green tea, but only in the morning). OTOH spouse did discover mental exercises that make dreams more vivid. Now sees sleep as entertainment rather than a waste of productive time.

  10. moarscienceplz says

    Jazzlet, what I am saying is that human sleep patterns seem to be both highly variable and pretty malleable, so declaring that biphasic sleep is our species’ natural mode and that those of us who don’t practice it are possibly harming ourselves appears to me to have very little evidence supporting it, and the fact that throughout history many people with many different occupations have chosen to spend half their nighttime hours with artificial light when they could seems to me strong evidence against that idea.

Leave a Reply

Your email address will not be published. Required fields are marked *