Segmented Sleep

“Historically human beings naturally slept in two distinct phases, with a period of wakefulness separating the two phases. There is evidence from sleep research, as well as from the reports of individuals, that this bi-modal sleep pattern, combined with a midday nap results in the experience of greater wakefulness during the day time, than uninterrupted sleep. During that period of wakefulness, the brain secretes high levels of prolactin, a hormone associated with a feeling of calm and well-being.

Historically this time of wakefulness between the two sleep segments was considered a special and even sacred time. Laborers tired from working the fields would have the energy to have sexual relations after their first period of sleep, people engaged in spiritual practices such as prayer, reflection and meditation, and others used the quiet time to read and write. Dreams were more available to be remembered during that time than upon awakening in the morning.” – Source 

We naturally slept in two or more segments


You can also sleep segmented at night and nap in the day. Read more about the benefits of day time naps in the the Siesta article.

“The historian Robert Ekirch summarized in his book At Day’s Close: Night in Times Past , the abundant historical evidence that humans previously slept in two separated segments.  This custom was common knowledge and there are many references to it. Here is an interesting passage from that article;

He unearthed  ”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 or smoked tobacco 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 labour 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. As the night became a place for legitimate activity and as that activity increased, the length of time people could dedicate to rest dwindled.”  – Source

“Many people wake up at night and panic, I tell them that what they are experiencing is a throwback to the bi-modal sleep pattern.” – Russel Foster


Some people might think they can simply wake up and go back to sleep, but this does not yield good results. Without at least an hour and a half  awake between segments, the body treats the two segments as one interrupted monophasic sleep the hormonal surge and sleep regulation does not happen. Jessica Gamble suggests that most people will spend two hours awake between segments, some people may be awake for more or less. Perfect timing doesn’t matter for this kind of schedule, not as much as other more hardcore schedules, so don’t worry about one or two nights that don’t allow you to sleep as you planned. But as always, consistency is healthy. Early to bed, Early to rise, with a few hours awake between, makes a man healthy, wealthy, and wise.

It is hypothesised that this segmentation is the origin of the ‘graveyard’ hours most humans experience – a sudden and strong wave of tiredness that hits around 3-4.30 AM. It is proposed that this wave of tiredness is caused by a surge of progesterone which causes sleepiness. This is a sign of healthy sleep, and supports the segmented sleep theory, as a segmented sleeper would need a physiological cue to take their second segment of sleep after being awake for a few hours.


There are many changes to the sleep architecture when you adapt to segmented sleeping. Normally SWS will be spread out across the night, but it will accumulate in the first three hours of your sleep, usually resulting in higher delta band activity and deeper sleep. Normally choline will fluctuate throughout the night, but when you wake up your brain will start to refill it’s banks of choline and when you sleep your second segment you will have cholinergic REM sleep, which means you will have more dense REM and will remember your dreams more easily, and more likely dream lucidly.

Light sleep will usually decrease, and your overall SWS and REM sleeps will increase, so some people may find they sleep less, others may find they sleep better.


There is evidence that the prolactin hormone surge associated with regular and stable night sleep segmentation can lead to improved sleep architecture, increasing restorative SWS in the first sleep, and increasing REM in the second sleep.

This prolactin surge in the first segment of the night can be regulatory of the entire day’s hormonal secretions! Having a high peak prolactin in the night, and repartitioning SWS into the first three hours of the night will mean there is less prolactin secreted throughout the day.

For the biology nerds:

Prolactin enhances the secretion of dopamine and hgh, which enhances the delta wave SWS. Prolactin also down-regulates sex hormones, so when the prolactin is high and blocking other hormones there effectively is a sex-hormone rebound when the prolactin secretion stops when you wake. When the prolactin stops and the rebound begins, the hypothalamus secretes gonadotropin-releasing hormone (GnRH). The GnRH will signal the pituitary gland to produce and secrete luteinizing hormone (LH) and FSH. LH orders the production of progesterone, DHEA kickstarts the production of testosterone (this is why most men get erections in the morning) and the DHEA combined with the progesterone raises body temperature and keeps the body warm at night.

This is all a very, very healthy process, as ideally testosterone is highest in the morning, and prolactin should not be produced in the day unless under very specific circumstances.

Monophasic sleepers will only produce a very small dose of midnight prolactin, or not get it at all, so the entire day’s hormone regulation becomes very sluggish, or doesn’t work at all! Testosterone does not get secreted until the later hours of the morning… some people will constantly produce small amounts of prolactin throughout both the night and the day to make up for lack of midnight surge which develops prolactin resistance and prolactinema…  prolactin interferes with other hormones which results in low testosterone, low estriol, low esterone, and high estradiol which results in fat gain… the dopamine system becomes exhausted and ineffective at producing GnRH resulting in low libido. Many doctors will attribute this to disease caused by general aging, but it could be a result of bad sleeping habits and forced monophasic sleep.

To reiterate, the result of no midnight prolactin surge is constantly secreted prolactin. Estradiol is needed to produce prolactin throughout the day. Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect, so is there an estrogen-type imbalance and effective estrogen power to effective testosterone power becomes imbalanced. It is most noticeable in women as they age. Not only does high effective estrogen cause fat gain in the belly, and chest areas, but it is also related to many diseases.


Early to bed, early to rise makes a man healthy wealthy and wise… some hours at night and a nap in the day keeps the diseases at bay. Have a 3-4 hours of sleep around dusk, and some sleep around dawn.

30 comments on “Segmented Sleep”

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  9. sigma Reply

    The biology of this sounds great. Have any athletes picked up on this? Seems like a segment-sleeping bodybuilder would have quite an edge.

    I’ll try this in the next few weeks and report on my progress here.

  10. Matt Reply

    The paper you cite as evidence for prolactin increasing REM sleep is not supportive. It says quite clearly in the abstract that the two groups, one with a prolactin-secreting hormone and one without it, did not differ in REM sleep, but only in slow wave sleep.

    • Adam Small Reply

      “REM sleep variables did not differ between the samples”

      I think this is the part of the abstract you are referring to. Are you sure this doesn’t mean that factors, other than the level of prolactin released, were similar in both groups?

  11. betty mayfield Reply

    Relieved to read this article. It accurately reflects my sleep pattern, which I was beginning to think unnatural and unhealthy. I entertained the idea that it was the result of having children (ie, having to care for a newborn at all hours), but in fact, this sleep pattern began with adolescence. For 35 years of marriage, I’ve been trying to deal with a wakeful period that arose 3-4 hours after I went to sleep. If I get up and read in another room, my husband senses my absence and his sleep is disturbed. So I tend to remain quiet in bed for my 2 hour wakeful gap. Meditation helps, but it’s been generally futile to attempt sleep. I now wonder if this wakeful period is an evolutionary product related to our need to be wakeful to meet the needs of infants and toddlers.

  12. Chrissi Reply

    I have a question:
    A sleep cycle take 1.5 hours. So two cycles end up in 3 hours.
    But why provides the segmented schedule to sleep 3.5 hours?

    • Atalia David Reply

      Yes it’s true, but you not asleep as soon as you are in bed right? Normally you need 14 minutes to go from awake to the first phase of the sleep. Maybe they put additional 30 minutes to make sure you get the right timing.

  13. Travis Reply

    As a 16 year-old, would this be advised (if plotted correctly) for someone who is in their last year of school to change their sleep pattern in preparation for exams, college etc.

    • Travis Reply

      I plan on doing:
      1st sleep: 10:30 – 1
      2nd sleep: 3 – 6:30
      Siesta: 5:30 – 5:50 or 4:30 – 4:50

      • Bethany Reply

        I’m a college student. I use generally it to my advantage to work on projects, homework, work on things I didn’t get finished before or study. Its pretty useful.

  14. Thomas Reply

    “DHEA kickstarts the production of testosterone (this is why most men get erections in the morning)”

    This isn’t true at all, men get erections as urine presses on the prostate from the bladder. Men generally get erections multiple times a night – that’s not testosterone cycling.

    Also, why is the primary source of these assertions another blog post?

  15. maz20 Reply

    Gotta admit, the two-sleep periods segmented approach appears to be my natural cycle and seems to be working quite well — though today is just my first day of it! Granted, I’m not so sure it will be as restful as a good monophasic sleep, since bunching all the sleep periods together will likely accomplish more in shorter time.

    But, polyphasic sleep does seem like a good adaption evolutionarily-speaking in that for “sedentary” days or individuals, they simply don’t need a lot of sleep to fully recharge mind and body. Your brain knows this, hence there’s not much point in it keeping you sleeping longer. For more active days/individuals, a solid monophasic sleep will likely be required for a full recharge.

  16. Vasco Reply

    I am a 16 yo who just recently learned about polyphasic sleep and I was wondering if a segmented schedule would suit me as a student and a an athlete.
    I can manage 2 core spanning from 23:00 to 7:30 a 20 minute nap around 14:00 and I am here to ask you guys how should I make my schedule and how should I adapt to that schedule.
    If you guys could help me that would be great!
    Thanks in advance

  17. Ariel Tarawally Reply

    I am also wondering if a segmented sleeping schedule will work for someone who goes to work early, or basically has to spend over 12hrs a day away from home. I am unable to plan naps during the day, I don’t think my lunch break (30 minutes) will allow me to conceal my sleeping schedule and avoid reprimanding. My idea was;
    1st sleep – 8:30pm to midnight
    Wakeful hours – midnight to 2:30
    2nd sleep – 2:30 to 5:30am

    Due to my commute and working hours I cannot plan a nap in between. the goal of my schedule was to have time to study, exercise, and meal prep. Ideally the activities would be interchangeable. All suggestions considered.

  18. E Reply

    Is hormone regulation just as good with the triphasic schedule than it is with segmented sleep schedule?

  19. cate Reply

    While this segmented sleep pattern is apparently supported by robust if old data, we don’t know at what ages it was practiced. Clearly our sleep needs and habits change dramatically as we age. Maybe this was only something commonly practiced at specific times of life, so that its not universally applicable.

  20. Ben Reply

    Does anyone know how humans used to wake up after their ‘first’ sleep? Was it just a natural response from the brain, and if so, does anyone experience this today?

  21. Muhammad Areez Reply

    I am a 15 year old finishing school and will be switching from a monophasic schedule to a segmented schedule with a 19-22-minute siesta. My examinations begin in a few days so I hope I can adapt quickly to not hurt my preparation.
    The schedule I am thinking of is:
    19:55 to 01:30 – 1st sleep segment
    01:30 to 04:00 – Wakeful hours
    04:00 to 06:30 – 2nd sleep segment
    At what time should the siesta be positioned? I will try 12:30 to 12:52 and see how it goes. I will post updates.
    Right now it is noon and I am going to take a siesta at 1:45 after lunch. I don’t know if I will be able to shift it back later.

    • Muhammad Areez Reply

      I tried to follow this somewhat but fell out of track. Couldn’t manage time. I am going to experiment again tonight.
      21:50 to 1:40 – 1st sleep segment (3h 50m)
      1:40 to 3:55 – Wakeful hours (2h 15m)
      3:55 to 6:35 – 2nd sleep segment (2h 40m)
      And probably a 22-minute nap after 12:00.

      • Muhammad Areez Reply

        Horrible adjustment because Ramadan has begun too. I am switching to a more triphasic-like schedule and will only update if success is achieved.

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