Will the ‘two sleep’ mode catch on again?

It is generally recommended that people get 7-9 hours of sleep per day but it is not clear that the benefits that accrue from sleep are lost if those hours are not in one block. Like many people, I often wake up very early morning before it is light outside and try to go back to sleep immediately, usually with some success unless something is on my mind that prevents me from falling asleep for some time. I used to think that this pattern of two blocks of sleep per night with a brief break was an aberration and that ‘normal’ sleep should consist of roughly eight hours of uninterrupted sleep.

But recently I have been intrigued by articles that summarize research that it is the one long sleep that is unusual and came about as a result of electric light becoming ubiquitous, and that before that nighttime sleep was in two parts separated by one to three hours of wakefulness in which people did whatever they wanted to needed to do. I wrote about this over seven years ago and now comes another article along these lines is by Karen Emslie that updates some of the information.

Modern, electrical illumination revolutionised the night and, in turn, sleep. Prior to Edison, says the Virginia Tech historian A Roger Ekirch, author of At Day’s Close: Night in Times Past (2005), sleep had been divided into two distinct segments, separated by a period of night-waking that lasted between one and several hours. The pattern was called segmented sleep.

Sleep patterns of the past might surprise us today. While we might think that our circadian rhythm should wake us only as the sun rises, many animals and insects do not sleep in one uninterrupted block but in chunks of several hours at a time or in two distinct segments. Ekirch believes that humans, left to sleep naturally, would not sleep in a consolidated block either.

Before electric lighting, night was associated with crime and fear – people stayed inside and went early to bed. The time of their first sleep varied with season and social class, but usually commenced a couple of hours after dusk and lasted for three or four hours until, in the middle of the night, people naturally woke up. Prior to electric lighting, wealthier households often had other forms of artificial light – for instance, gas lamps – and in turn went to bed later. Interestingly, Ekirch found less reference to segmented sleep in personal papers from such households.

When people wake up around 3:00 or 4:00am, they often try to force themselves back to sleep and get stressed when they cannot, which hinders sleep even further. Emslie suggest that we should embrace that early morning wakefulness to do various things before going back to sleep. The catch is that our work days often require us to get out of bed at around 6:00am or so and that prevents us from finding time for a couple of hours of activity before the second sleep block. Of course, we could go to bed earlier like people used to do, say around 8:00pm, and then when we wake up after four hours of sleep, we can do stuff for about two hours and then get another four hours of sleep before waking. In other words, we shift what we would normally do in the late evening to the middle of the night.

But so much of modern life is centered around the late evening hours that this two-sleep routine may not be feasible except for the few who can sleep until later in the morning. Now that I am retired and can sleep as late as I want, I am tempted to try this out because it will still allow me to keep to my current bed time of around 11:00pm.

Via Seamus Bellamy, I came across this fascinating video by former NASA astronaut Mike Massimino about sleeping in space. He says that the astronauts are encouraged to work on an Earth schedule of 24 hour ‘days’ even though a ‘day’ in orbit only lasts 90 minutes. This regimen includes encouraging them to sleep for eight hours. I wonder if the astronauts might be better off being advised to sleep in two blocks of four hours with activity in between.


  1. Pierce R. Butler says

    Given my druthers, I live electrically -- usually reading books or web-browsing until well past midnight. When unable to avoid morning work, I adapt fairly well to early-rise/early bed, but always revert quickly as soon as the pressure to do that goes away.

    This pattern feels innate to me, and I wonder whether pre-Edison “night people” for millennia lived lives of circadian maladjustment, a wealthy few among them making do with candles or whale-oil and whatever tasks they could handle with same.

    Sometimes I wake at dawn, go back to sleep in what seems a short time, and re-waken a few hours later feeling much more refreshed than otherwise. Perhaps I could rig a computer to do something to that effect…

    Tangentially: in the ’70s I read of an “alarm” clock which used gentle and harmonic sounds, gradually increasing in volume, rather than a loud and genuinely alarming burst of noise. That this design did not immediately and permanently predominate proves, yet again, that “the market” does not select for superior products.

  2. anat says

    About 6 years ago my husband experimented with some form of segmented sleep. After a few days he fell inexplicably ill and instead went off caffeine cold-turkey. (He couldn’t tolerate coffee while ill.) As a result he is more alert and more capable of efforts that require being alert for long stretches of time such as long distance driving. Instead of trying to reduce the time he spends asleep he discovered ways to have more vivid dreams, so now his sleep time is more entertaining.

    I might be a natural candidate for segmented sleep, as I do tend to wake up and stay awake for a while most nights. Though I’m not sure if that would be a good thing for me to try as I am working on being less sleepy during the daytime. One thing I learned recently is that sleeping on one’s back, as I have done since my teens results in ineffective sleep because it renders the glymphatic system ineffective. Now I am teaching myself to sleep on my side, and while my shoulders are uncomfortable and I need to fully wake up in order to turn over I do seem to be less sleepy.

  3. mnb0 says

    “I used to think that this pattern of two blocks of sleep per night with a brief break was an aberration ”
    Then I’m an aberration, because I hardly ever sleep an entire night in one go, almost as long as I remember. NowI’m getting older I sometimes have trouble falling asleep again and that can be highly annoying. In that case a siësta may help me out.

  4. johnson catman says

    Pierce R. Butler @1 re alarm clocks: Many years ago, I lived with a woman who had an alarm clock that used a light that gently came on and off with increasing intensity until you cut it off. Many mornings, I found myself incorporating a blinking light into my dreams as I was just awakening. That was the only time I have been exposed to a non-conventional alarm. I use my phone now for my alarm, but many mornings, I wake before it goes off and turn over for a few minutes more rest.

  5. anat says

    Pierce R. Butler @1 and johnson catman @4:

    The alarm system my husband uses is controlled by a sleep-monitoring device called https://en.wikipedia.org/wiki/Beddit The Beddit identifies what stage of the sleep cycle you are in based on your heart-rate and breathing patterns. It looks for a time you are entering light sleep within the 30 minutes prior to your wake-up time and wakes you up then using the sound of your choice, starting softly and increasing in volume. This means that most days he is woken up at a time his brain is ready to wake up. Only on days when he is in deep sleep the entire 30 minutes prior to the designated alarm time does he experience the rude, unpleasant awakening. As a result, although most days he awakens earlier than planned, on those days he feels more refreshed.

  6. says

    I used to think that this pattern of two blocks of sleep per night with a brief break was an aberration and that ‘normal’ sleep should consist of roughly eight hours of uninterrupted sleep.

    Humanity’s attempts to establish prescriptive norms for everything are harmful. “This one option is ‘normal’ and everything else is an ‘aberration’” is an unhealthy attitude. As long as some person feels well-rested and comfortable, anything goes. There should be no prescriptive norms about how people are supposed to sleep.

  7. brucegee1962 says

    I always used to wake up for a while in the middle of the night. Then I was diagnosed with sleep apnea and got a CPAP machine. Now I sleep through the night pretty much every night.
    Just my 2 cents.

  8. Pierce R. Butler says

    johnson catman @ # 4 -- That reminds me of one of the waker-uppers in the classic James Coburn spy parody Our Man Flint, which focused a light beam onto his eyelids. (Left unexplained was how the beam found his eyes at the right time on an undulating and quite large bed shared with four women…)

    Flint also had a watch which extruded an arm with a pair of tiny prongs that poked lightly at his skin, sufficient to wake him from a self-hypnotic trance deep enough to fool the bad guys into thinking he was dead. That one I might like, depending on how much adrenaline such a stimulus might produce.

    anat @ # 5 -- fascinating, especially since it doesn’t require cables or a headband. Alas, the $150 price tag and reported partial incompatibility with waterbeds create serious impediments to me experimenting with a Beddit (the corporate-speak “Measure, manage, and improve your sleep” slogan somehow fails to appeal either); others may find the iPhone requirement a deal-killer.

  9. Timothy says

    +1 for At Day’s Close: Night in Times Past.

    It’s a fascinating read.

    @ #7 -- I, too, sleep much better having been diagnosed with sleep apnea and having a CPAP machine.

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