How to Conduct a Personal Experiment: Biphasic Sleeping

It’s time for another edition of “How to Conduct a Personal Experiment.” Last week, it was the cold water plunge. Today, we’re going to talk about running a biphasic sleep experiment. First, though, I’d like to know: how are the cold plunges going? Are they, well, cold? More importantly, did you have any difficulties setting up the experiment, identifying variables, and choosing what to measure and track? This whole personal experiment stuff is likely new to most of you, and while there’s no real “wrong” way to go about it, there will be some initial difficulties. Be sure to keep us posted in the comment section.

Okay, on to the new experiment.

Biphasic sleeping is exactly what it sounds like – two-phased sleep. Instead of monophasic sleeping, which is sleeping in one big unbroken block of time, biphasic sleeping is broken up into two chunks of time. I wrote about biphasic sleeping last year, explaining how considerable evidence suggests that biphasic sleeping is actually the natural sleep pattern in humans. Before the Industrial Revolution, back when darkness meant bedtime and keeping the light on after dark required the consumption of expensive candles and lamp oil, people had far more exposure to darkness. They didn’t have iPhones, laptops, big screen TVs, or even lightbulbs. They had the moon, the stars, the campfire, or maybe – if their city had implemented them – street lamps that were really just candles in glass. And this shorter photoperiod resulted in a very different way of sleeping:

You’d get to bed shortly after darkness had fallen and sleep for several hours. This was “first sleep” (later mistranslated as “beauty sleep”). Sometime around midnight, you’d wake up. You’d putter around, read a little by candlelight (if you were literate and could afford candles, that is!), make love, get up and dance, check on the animals, talk with friends or folks in your tribe, think of stately pleasure-domes in a partial waking dream state… that sort of thing. In short, you would be awake and at least moderately active. You’re not a groggy, grumpy person here, fussing with your pillows, thrashing at the comforter, and agonizing over the alarm clock. You’re reasonably alert and cheery.

Then you’d drift off to “second sleep.” Sounds cool, right, but out of the realm of possibility for us living now? Maybe not.

Studies find that modern humans living in an technological permaglow of light will revert back to the biphasic sleep pattern when exposed to shortened photoperiods (from 16 hours of light to 10 hours of light), so the potential remains.

But very few of us are humans living in contrived study settings, and that’s what could make this one a little tricky. Ideally, biphasic sleep is effortless. It just happens. You wake up, read, talk, use the loo, or do something gentle for a few minutes or a couple hours, and go back to sleep without actively trying to make it happen.

That won’t work for everyone, not without active intervention and formal experimentation. Which brings us to the personal experiment.

But why biphasic sleep?

Mostly because I find the notion that we’re all “doing it wrong” when it comes to a fundamental aspect of our lives – sleeping – extremely interesting. I mean, it’s not like it hasn’t happened to us before (diet and exercise, anyone?). It’s not out of the realm of possibility. I’d even say it’s fairly likely that we’re getting something wrong when we sleep, seeing as how 60% of Americans between the ages of 13-64 report having a sleep problem almost every night, whether it’s waking up feeling groggy or waking up too early. Even those of you who are clued in to the whole Primal thing might find it helpful to explore another way to sleep. In my last post on biphasic sleep, I referred to it as more of a thought experiment than anything else, but today I’m recommending people formally attempt to integrate it into their lives, if only for a month or so.

That said, is there more than one type of biphasic sleeping? Sure:

Natural biphasic sleep

This is what I call normal human biphasic sleep – two four-hour blocks of sleep broken up by an hour or two of wakefulness in the middle of the night. Easy to understand, if hard to implement.

Modified biphasic sleep

This is the kind of biphasic sleep that lifehackers employ. They’re not really interested in anthropological or evolutionary arguments for sleeping a particular way; they want to save time and get the minimum dosage of sleep that confers the maximum amount of benefit. They see sleep as a waste of time, albeit a necessary one. From what I can tell, lifehackers typically sleep for a 4.5 hour block of time – say, from 2 AM to 6:30, which allows them to stay up late, get three, full 90-minute sleep cycles in, and rise early to greet the day. They follow up with a 90-minute nap sometime in the late afternoon, which gives them another 90-minute cycle and enough energy to make it to the next sleep block.

Sidenote: I’m somewhat skeptical of these shortcuts when it comes to sleep. From what I can tell, they focus on REM sleep and seem to classify non-REM sleep as “wasted” sleep, as if it exists only to propel us from one REM session to the next. Eh, I’m not so sure we should be so flippant about messing with a vital physiological process, nor should we immediately discount the importance of “useless” sleep. I have no problem with hacks, usually. In fact, I usually welcome them. Just be careful when hacking something like sleep.

Okay, so how do I do it?

First, you want to determine what kind of biphasic sleep pattern is even possible for you. If you have the freedom to get to bed shortly after dark, wake up in the middle of the night for a couple hours, and go back to bed, go for natural biphasic sleep. 

  1. Choose an “absolute latest” morning wakeup time. If you have to be up by 7 AM, that’s going to determine how late you can go to bed.
  2. Determine a bedtime. It should be at least nine hours from bedtime to morning wakeup time, giving you two four hour sleep blocks and one hour of free time in between. If you’re up by 7 AM, you should be in bed by 10 PM. If you want another hour in the middle of the night to do stuff, go to bed by 9 PM.
  3. Reduce exposure to artificial light once the sun goes down, or at least two hours before your scheduled bed time, just like it would have been for most of human history. Turn off the TV, install f.lux on your computer, light some candles, and/or wear blue light-blocking glasses or goggles. It probably won’t work as well otherwise.
  4. If you use lighting during your mid-phase waking period, be sure to wear blue light-blocking goggles or stick to a natural light, like candle or yellow light. Try not to bust out the PS3 for some online gaming.

If you need more alert waking time in a day and would like to try reducing the amount of sleep you require, try modified biphasic sleep.

  1. Choose a 4.5 hour block of time. This will be your “anchor” block of sleep, and most people have success placing this at night or during early morning. Try 10 PM-2:30 AM, perhaps, or 2:00 AM-6:30 AM. Set an alarm, at least until you become entrained to that schedule.
  2. Wake up and go about your day. Get some light exposure, preferably daylight if applicable.
  3. Take a 90 minute nap, to begin 8-10 hours after your wake up time. If you woke up at 6:30 AM, you might nap from 4:30 PM-6 PM.

Set a realistic goal:

  • “I want to improve my sleep.”
  • “I want to feel just as refreshed on less sleep.”

Come up with a hypothesis, like:

  • “Modified biphasic sleep will reduce my sleep requirements while maintaining my wakefulness, productivity, workout recovery, and immune function.”
  • “Natural biphasic sleep will reduce my nighttime anxiety about waking up and ruining my sleep, thereby improving my sleep.”

Now, we identify some of the variables and think about how they might affect the outcome:

  • Length of sleep blocks – Are four hours enough during natural biphasic sleep? Do you prefer two three hour blocks instead of a 4.5 hour block and a 90 minute nap?
  • Timing of sleep blocks – Do you need less time in between the anchor block and the nap? How do you sleep with one hour between your two sleep phases? How about two hours?
  • Alarm – Does the alarm help or hinder your biphasic sleep?
  • Light – How does light exposure affect the effectiveness of your biphasic sleep? Is total abstention before bedtime necessary?
  • Activity while awake – What are you using your free awake time to do? Does reading by candlelight have a different effect on sleep quality when compared to going for a walk?

Next, let’s take some measurements. What to measure?

  • Productivity – Is your work suffering or improving? How many productive hours are you getting?
  • General wakefulness – How are your energy levels throughout the day? Are you getting a mid afternoon slump? Use a simple 1-10 scale.
  • Grogginess – Do you feel well-rested upon waking? After which phase do you feel the most rested? 1-10 scale.
  • Recovery – How are your workouts? Are your numbers improving or falling?
  • Immune system – Are you getting sick more often?

Try the biphasic sleep for at least a week, preferably closer to four weeks. Then once you’ve established a baseline and have some data to work with, refer to the list of variables above, make a change to a single variable, and give it another try for some duration to see if biphasic sleep is for you.

This isn’t for everyone. As Robb Wolf points out, when you have 14 hours of uninterrupted darkness and potential sleep time, you have the luxury of being a little more picky with your sleep patterns. When you don’t have emails to answer or an unprecedented renaissance of quality television to tear into, you’re going to get sleepy when darkness falls, go to bed pretty early, wake up after several hours, do your thing, and go back to sleep for another several hours. Biphasic sleep is probably natural. But we’re not living in very natural times. Or, if we are, natural means something different from what it once did. That’s the whole premise of the Primal Blueprint, after all – identifying what our ancient genes expect from the environment and figuring out how to modify our modern environment to fit those genes.

Let me know what you think in the comment board, and be sure to check out today’s contest.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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101 thoughts on “How to Conduct a Personal Experiment: Biphasic Sleeping”

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  1. Awesome post Mark!

    Years ago I trained for a marathon during the hot summer months and preferred to do my long runs at 4am to beat the heat. My life didn’t allow me to get to bed super early so I started biphasic sleeping. I slept usually from 11 to 3:30 and then took a couple hour nap after work in the late afternoon.

    It was great. I was never tired, even with my demanding running schedule. And I really enjoyed the different schedule.

    I’ve been thinking about taking it up again in my later months of pregnancy (so I’m happy to see this post), both because I often have to pee at 4am and because it would be good preparation for having a little baby around. 😉

    1. This is exactly what I do every summer, nap every day, and I love it! I get up, do a training run, get some chores done, nap, and then get up for the rest of my day. LOVE IT!

      But I’m a teacher and can only get away with it in the summer, unfortunately. There is no “nap time” built into the school day anymore. 🙁

  2. I just said last night that if I want to get everything done I’m going to have cut back on sleep. There is very little else I do that can get elimnated. Maybe this is the answer!

  3. This is very interesting. I’ve been going to sleep at 10 pm, waking at 2 am, reading or puttering around for a couple of hours, then going back to sleep at 4 and getting up at 8 or 9 for a few months now. It just happened naturally and I just thought there was something wrong. I had no idea it was considered a “normal” sleep pattern. You learn something every day. Since I work from home and have the luxury of choosing my own hours, I’m just going to continue doing what my body seems to want to do.

    1. So you just randomly began waking in the middle of the night consistently?

      Do you have more energy during this type of sleep?

      I am very interested in trying this experiment out. I can’t start but may do this once I land in Olympia in 2 weeks!

      So, I’d love to learn about more experiences.

      1. Primal Toad,

        You might find it hard to get to bed early enough without blackout shades in Olympia in the summer as the days are long in the PNW (it is usually still pretty light at 10:00 pm, especially on clear days, and bright again at 5:30 am). Much easier to do in the winter months where there are barely 8 hours of daylight…which is mostly clouds. 🙂 Long days equal more time for fun after work…but bad on your sleep cycle. Haha…

  4. Ok, sounds great except it takes hours for me to simply fall asleep… Ambien made it better but still.

    I sleep about 4/5 hours a day and I can call THAT a good night o’ sleep.

    1. I gave up on drugs for going tosleep when I went primal. I have tried them all in trying to deal with sleep issues. I have found Magnesium and Melatonin now do the trick to help me into sleep. Recently I have been using an autohypnosis track to help me ease into sleep- the Iphone allows me to set it for 90 minutes or so, so I don’t listen to an endless loop. This helps expedite going to sleep, and seems to keep me asleep longer.

  5. I’m glad you’re sharing these guidelines and suggestions for personal experiments. This one is equally as compelling as last week’s for me for I just realized my poor, SAD, exhausted body did this naturally for a while about 8 years back. Commuting 3 1/2 hours a day to a long and stressful job, mothering my young child, and the various household chores & cooking was a great stress on me back then . I’d find that I’d literally ‘pass out’ (well, fall asleep), after my son’s bedtime for about 3-4 hours. Then I’d naturally wake up and do some household chores for an hour or two, then get back to bed for a few more hours of sleep.

    I’m definitely going to try this experiment now that I’m travelling a calmer, primal road.

  6. I would LOVE to do this – I’m working two jobs over the summer in an attempt to take on as low a student loan amount as possible, and there are never enough hours in the day to get all my work and chores done and also get enough sleep to feel ok. I just moved from the country to the (loud, bright) city and will be installing light- and noise-blocking curtains sometime this week, which should help a bit with getting uninterrupted sleep, but needing fewer hours overall would be amazeballs.

    A question for anyone who feels inclined to answer: my two jobs are as a programmer and a baker, so I’m inside all day (anywhere from 7-15 hours at a time), either under fluorescent kitchen lighting or staring at a screen. I’ve already started scheduling 5-minute breaks to walk around my building when I’m programming, but I can’t do the same at the restaurant. Will this much exposure to this kind of light make it harder for me to try polyphasic sleep? I already use as few lights as possible when I’m at home and am planning to get some oil lamps to use in the evenings, but I spend much less time there, unfortunately.

    1. Sounds like awesome experiment controls to me! Let us know how you think it works out.

  7. Very interesting article! It’s fascinating to hear how this has worked for other people, and we like the idea of a more “natural” sleep routine.
    And naps are pretty great!

  8. This is what I naturally do during the winter months. I’m generally asleep (or fighting it) shortly after dark, wake up around midnight, get up and do a few things, go back to bed an hour or 2 later and sleep for another 2-3 hours. I thought it was a problem. Who knew?

    1. When I lived by myself and could control my environment I tended to get ready for sleep when dusk arrived, wake up in the middle of night for a spell, and then awake with the sun. This is the only way I feel refreshed in the winter. But now with a full house, no deal.

  9. When I was (much) younger I worked in a pub until midnight and started work as a breakfast waitress at 5am. I caught a few hours between jobs and then again a few hours later. It was awesome even though I usually got only 6 hours sleep.

    These days, I often wake at 3-4am, get up and do some work then go back to bed for a few hours or simply stay up and nap later in the day. I *never* feel tired if I do things this way and now regard my early morning wakings as a gift.

  10. I’ve been doing this ever since I got a puppy with a “tiny bladder”. He’s now 9 years old and he still needs to go outside to pee in the middle of the night. So sometime between 1:00 and 3:00 in the morning he’ll wake me up (and the other two dogs) and we all have about a 15 minute potty break. I don’t turn the lights on, so it’s easy for us all to fall back asleep when we’re done.

    1. Hah — some of us can’t blame the tiny bladder on the dog!

      I did notice that last night I went to sleep around 8pm, woke around 12:30, and again around 5am — that one WAS the dog. We went out and back to sleep and slept until 7:30. Probably 10 1/2 hours sleep total and I feel great this am.

  11. I wake many times a night to nurse my toddler. Since he was a baby he sleeps a few hours first, then the rest of the night is much more unsettled with lots of nursing. This seems the norm among friends who co-sleep and breastfeed. The obsession people have with ‘sleeping through the night’ is clearly expecting too much from an infant!

  12. When in central Africa with no artificial light I slept better than ever before. My husband would often wake in the night and chase rats around the hut with a machete! Now I know why.

    1. LOL “chasing rats around the hut with a machete”… I think I might need to make this a euphemism for some mid-night activity…

    2. Hahaha! Thank you for the mental picture. You totally made my day.

  13. This is an interesting post since my sleep patterns follow daylight. In the wintertime, I have no problem going to bed early 7pm reading for a little bit and sleeping for 11 hours or so. In the summer, I can’t go to sleep if it’s still light so it’s usually not until around 10pm then I’m up again at 5am. Since I do best in 9 hour of sleep realm, I usually take an afternoon hour or so on the weekends, in the summer.

  14. I seem to follow this biphasic sleeping pattern only to be told by my naturalpath doc that this is stressful due to cortisol out of wack and recommends supplements to help me get a better nights sleep to normalize my hormones. I would love to jump put of bed and have a ton of energy. I don’t have any coffee or tea. I am so confused what should I be doing ?

  15. I do this almost every night! It’s called having a newborn. 😉 All joking aside, since going full on primal with diet and activity after her birth, I have noticed that despite my sleep being interrupted through the night (for anywhere from half an hour to an hour), I’m not a grumpy groggy mess in the morning. On the contrary, I am up and ready to tackle the day with my 2 year old son and my baby girl. 🙂 I think you may be onto something here, Mark….

    1. I am the opposite. I’ve four little ones (6yrs – 4months) and I co-sleep, but I am “waking” every two hours (or more)to nurse. Even though I exercise and our family has switched to being Paleo… I am exhausted, cranky, always hungry, and stomach burns.
      I can’t tell if it’s just allergies, my body adjusting to new eating habits,the lack of darkness (live in AK), stress, or the constant nursing wearing me down? Sleeping more and feeling great would be wonderful!
      I’d like to see Mark do a post in regards to nursing mothers and how we can stay fit (getting into all my pre-baby clothes would be awesome too!)stay awake, and over all being Paleo while nursing (and even pregnant).

      1. 4 month old babies feed a lot, make sure you’re eating enough. And 4 under 6? Enough to wear anyone out!

        1. Have to agree with this one. Price’s studies were enough to convince me to space kids at least 3 yrs apart. One great line from his study in a remote pacific island was that husband and wife sleep in separate huts until the newborn reaches two or three years, at which point the child no longer need their mothers exclusive attention, and the mother has recharged her vit.A supplies needed for the health of the next baby. Husband and wife can then get together again.
          The line among the tribe was something like ‘If this protocol isn’t observed then the parents deserve everything they’ll get.’ Hardly fashionable with CW,
          nor help to Megan- sorry! But keep it in mind breeders…

      2. you are a perfect candidate for Dr Kruse ‘s cold thermogenesis protocol. The cold triggers leptin to replace the normal light/dark signals. Living in AK gives you access to cold water sea food and plenty of cold water/air to convert WAT to BAT. One big caution is not to kill too many fat cells as they will release their stored toxins when they die, not great for breast milk.Your sleep will improve dramatically and so will your kidd’s

      3. Sorry to hear that you are having some troubles, Megan! 🙁 My daughter was born with Pierre Robin Sequence and a Cleft Palate. Due to her inability to get any suction, she was unable to nurse and we have to feed her with special bottles. Even with pumping, I was unable to keep my milk in, so we were forced to supplement with soy formula. My milk never came in fully for my son, either, so I’m not sure why I’m broken in that regard? 🙁
        Anyway, this obviously means that I am not up ever 2 hours to nurse, more like every 3 to 4, but I am always on ‘mental alert’ listening for her breathing or if she swallows her tongue/chokes on spit up due to her condition. If I sleep too well, I sometimes wake up in a panic to check on her. We don’t co-sleep, but she is in her crib less than 2 feet away from me.
        Anyway, I’m not sure why it works for me, but I consider myself incredibly lucky that I have the energy to deal with my toddler, my baby girl, and keep the house without having a meltdown. I hope that you are able to figure out what works best for your body soon! Sounds like there is a bit of tweaking that may need to be done?
        Take care!

        1. N3P3N7N3, it made me so sad to see your comment about being “broken.” I have had several friends with supply issues and I can barely imagine how awful and frustrating that must feel (my first LO is almost five months old, so I totally get the overwhelming new-mom guilt, regardless of its source). But you are NOT broken! Many, many women struggle with low milk supply due to a huge variety of causes, both genetic and cultural. In most hunter-gatherer societies women typically co-nurse the babies of close friends and relatives, so a single mom with a low milk supply would still successfully raise a healthy baby. That’s part of why the problem is so common, since the genetics that may contribute to it are still with us today. Unfortunately there are a lot of institutional structures that compound the problem and since we no longer co-nurse, many mothers have no choice but to use formula. But you are NOT BROKEN! You are the best possible mom to your LO and she is so lucky to have you!

        2. As Basbleu said, the issue of not being able to supply enough milk is anything but rare and does not make you “broken”. My wife fought hard to breastfeed our son but it was clear he wasn’t getting anything and was going hungry. It was frustrating her, making her sad, and worrying us — and leaving him hungry.

          Tons of mothers have problems breast-feeding. It’s so very common you really shouldn’t be worried about it at all. When we finally realized it, and stopped thinking it was “Gods Plan” that our son be breast-fed, the guilt associated with it went away. We embraced formula, and are now so grateful that God/nature created some really smart people to create a pretty decent product called formula in order to help us.

          Our son has only ever been formula-fed. Yet he’s slightly taller than average, strong, active, healthy, and smart as a whip (he’s now 2-1/2). I’d say the formula works pretty well. Of course, breastfeeding is better if you can; but if you can’t, formula is amazing and you shouldn’t be ashamed or feel “broken”.

          The fact your baby has such a caring mom is proof you aren’t broken.

      4. Hi Megan,

        I think it makes a difference whether you wake up by yourself (naturally) or because your little one wants mommy/nursing time. The two of you are of course attuned to each other, but when you’re awakened in the middle of deep sleep, 3-4-5 times a night, that can really make you foggy. I remember feeling overall tired, but not specifically in the mornings. Usually I still hit the 7 hours of sleep. Obviously it’s not only about the amount, but also the quality. And the demanding day-job of having small children. I really hope you do find something that helps you a bit. In the meantime it always helped me te hear that others are having the same “problems”, that way I could “let go” and just go with the flow, assuming that it always gets better and I could do this. The best of luck to you.

        1. Thank you guys so much for your kind words. I got a bit emotional over them, as this subject is a bit taboo among my friends. I felt so pressured by them to exclusively breast feed, and when we realized that little Evey was never going to be able to latch or get suction due to her cleft palate, I felt heartsick over it. And within days, I was unable to produce enough milk for even one feeding, and I was so depressed. I thought this pregnancy/post pregnancy would have been different than with my son because I was healthier this go around. Alas. And like you, Brandon, our son was exclusively formula fed, is almost 3, 95th percentile for his height, and too smart for his own good. 😛 So I shouldn’t complain.

          Thank you all again. This is a great community, and I love that I can rely on you all for a fresh perspective. *group hug* 😉

  16. I would love to do this! I have been trying to go to bed earlier, but unfortunately I watch TV or play on my phone before I settle down. It would be nice to get the hubby on board and play a card game, read, get busy, or whatever by candlelight. It makes me want to go camping even more to get away from all of the electronics and artificial light. 🙂

  17. A lot of professional world-class boxers follow a biphasic sleeping pattern. They get up in the morning, do some cardio and/or training, then go back to sleep for a few hours. Afterwards, they train again.

    I imagine a lot of athletes do something similar.

    Of course, there are always those contrary to the norm. For instance, welterweight champion Floyd Mayweather is a nocturnal being. He rises in the afternoon, then trains, relaxes, and sleeps in the wee hours of the morning, i believe around 7am. As Robb Wolf suggests out, electricity gives us options.

  18. with five kids under the age of nine, I have been doing biphasic sleep for nine years now – it sucks. I guess it’s different if you wake up on your own schedule? I feel like I never fall back into a deep, restorative sleep for the second (or third) phase.

  19. I agree that ‘societal expectations’ about sleep patterns is a ridiculous idea from the get-go. Peoples’ individual sleep requirements are all over the map, and it’s ludicrous for anyone to make a pronouncement about blanket requirements. Some people are extreme Type A, or genetically suited to needing short rest, and need only 3 hrs/night; I need 9, but probably since I’m up 3x/night to pee (small bladder).

    But seriously, “Lifehackers”??? These people are the opposite of everything paleo/primal stands for: productivity-driven computer programmers. I can’t think of a more unhealthy group (sitting in a chair before a monitor blasting Twinkies and Red Bulls all day), nor think of a group who’s life goals reflect mine less.

    I see some economics-driven, hectic-lifestyle stressing in the above comments that seem to be the motive behind possibly embracing biphasic sleep. Sounds like one more attempt to adapt people to a stressy way of living, rather than to clean up one’s life to suit one’s inate primal needs.

    1. I think you are making a bit too many generalizations and presumptions on this.

      I’m a programmer. I code Java/HTML/JS apps all day long for a major university. On the side I’m writing an app for my local food co-op.

      I’m a big paleo fan.
      I’ve converted my wife, my son, and warmed large parts of my extended family — none of them are programmers.

      I’ve gotten a few people at my work moderately interested in paleo, two of them to a fair degree.

      Aside from paleo, we have quite a few who actively try and eat healthy, get out of doors frequently, and exercise regularly and don’t regularly eat Twinkies or Red Bulls.

      And let’s not forget that this fabulous website which Mark uses to share such awesome info with all of us was built on the backs of… “that most unhealthy group of programmers who blast Twinkies and Red Bulls all day”.

      C’mon… every segment of our society is unhealthy and in every group there are those likes us trying to become better… yes, even among us *HORRID* computer programmer types (GASP!).

      1. Alright, alright. I shoulda put in the LOL or the :o). My apologies!

        Congrats and well-wishes on your being paleo. Hope you represent the future norm of programmers. That is a lot better than ‘productivity’ (an often-abused management concept) being the end-all.

        1. Haha. Fair enough. 🙂

          Incidentally, where I work quite a few of us younger-gen coders strive to lead healthier lives than many of the older-gen ones. Arguably, many go about it wrong (quite a few are vegans or workout-a-holics), but they are aware of the need to strive to be healthy. I find that encouraging.

  20. I think I’ll skip this one. I fall asleep usually by 9pm, sometimes earlier, and sleep like the dead until dawn.

    1. I think I fall into this category, too. I’m looking forward to two weeks of vacation to give this a whirl, though, when I don’t need to worry about mine, or anyone else’s, schedule.

    2. Yup, I already give myself a 9-10 hr block for sleep and generally sleep straight through. I sometimes take naps in the afternoon too. Although it might be cool to be up for a couple hours when all is quiet I would then need to sleep til 10 am instead of 8.

  21. This has been a natural way of sleeping during many phases of my life: as a high school student also working 30hrs a week; as a breakfast waitress and daily mountaineer; and of course as a mother of young ones.

    When I find myself in a pattern where sleep deprivation is becoming the norm, carving out a block of 1-3 hours for a nap is a life saving tool.

  22. Without realizing it, I used to do biphasic sleeping in high school. I’d come home from school in the mid-afternoon and sleep 3-4 hours. Then I’d get up, join the family for dinner, be awake and alert for my homework, then return to bed in the wee hours for another 4-5 hours.

    It was great. Now when my occasional naps last too long I’ll consider it a split-sleep night, and still wake up refreshed the next day.

  23. I wouldn’t underestimate the importance of 90 minute increments. I have personally found this to be a reliable measure, and if I am woken up in the middle of one of these, I feel epecially groggy. I would recommend that each phase be a multiple of 90 minutes of actual sleep instead of four hours. And they don’t have to be equal. You could make one three hours and the other four and half.

  24. North of age 55, most people will enjoy the benefits of biphasic sleep courtesy of their bladders. But that aside, I was diagnosed with complex sleep apnea 9 years ago, complex being the combo of obstructive and central versions of apnea. With treatment, including a CPAP, I now enjoy the benefits of biphasic sleep. 9:00 p.m. to 1:30 a.m. and 2:30 to 5:00 a.m. Not only has my overall sleep hygiene improved as compared to all of my previous adult life, my waking hours are more energetic and I find that when I wake, I WAKE. No need for stimulants or protracted periods of “revving up”. I would highly recommend a biphasic sleep regiment

  25. Very interesting. How are suppose to sleep during summer months when there is not that many hours of darkness ( dark for four hours) ? Should you sleep less?

    1. I have been wondering about that myself. If I were to sleep when it is dark and wake when its light, I would never sleep in the summer and sleep all the time in the winter. Right now, it gets dark around 10:30pm and is getting light again around 5am(or earlier). During the middle of winter it doesn’t get light until mid morning and is dark by 4pm, although much if the time the sun is hidden all day.

  26. I am so excited to try this! For weeks, I’ve been wide awake between 3:00 – 3:15 AM. Every damn night! Doesn’t matter if I go to bed at 10 PM or 1 AM and doesn’t matter how tired I am. Then, I wrestle with the pillow until 5:00 or so when the birds announce the day. I’ve been staying up later to try to force exhaustion but maybe I’d be better off hitting the sheets as soon as the sun sets and just plan for a 3:00 am break. Heck, even if I only get another hour of semi-sleep before morning, it’d be better than what I’m doing now. Thank you for the suggestion!!

  27. I just go to bed when i’m sleepy, and wake up when i’m rested. This may mean i wake at 4am sometimes – it may mean i skip a day too, lol!

  28. Reading all these comments I’m amazed by how many people already have some sort of biphasic sleep pattern (and think they have a sleep problem!) I also wake up after 3-4 hours of sleep; unless I get up and do some yoga or move around I cannot get back to sleep. I always keep the lights off and just wander around the house/stretch/drink some water in the dark. I like having the place to myself, and when I go back to bed I sleep like a baby til morning.

  29. I have slept with this concept for sometime and I thoroughly enjoy it… That 8 hour crap is for the birds.

  30. Didn’t I read on this site, that this 1-2 hours of semi wakeful time is when your body releases HGH ? What would the effect of actually becoming active Be?

  31. Funny, I was just reading a particular passage in “The Primal Blueprint” book on Grok and family napping by the river in the mid-day.

    My sleep doesn’t always have me feeling rested and I often feel like I would benefit from an afternoon nap. I’ll give this a shot!

  32. I usually set my alarm for 7 – 8hrs, but almost always wake up after 5 – 6hrs. I read the news and MDA in bed right after I wake up, and if I’m really tired after my hour or so of reading I’ll sleep about 90mins more.

    If I sleep more than 7 1/2 hrs in one phase I usually feel like I have the flu w/o fever and walk around like a zombie all day. If I oversleep in my second phase this also tends to happen. My most energetic days are usually when I’ve slept less than 6hrs.

  33. This really sheds light into ‘siesta’ cultures. I live in one now and could never figure out how everyone was staying up SO late and still waking hours before me… Finally I realized they all sleep in the afternoon! It seemed silly to me at first, but I guess it isn’t so crazy after all!

    1. Good point. I made the comment below that I sleep very heavily during the winter months, requiring lots of hours, and very lightly during the summer months.
      There might be a link between biphasic sleep and the phenomena of “siestas” in warm/hot countries with lots of sunlight and heat.
      Did the Inuit have biphasic sleeping patterns? It would be interesting to find out.

  34. During the summer months, I tend to go to bed at 11 pm and I’m usually naturally up by 6:30 am (no alarm) cause of the sunlight.
    During the long, dark, Canadian winters, I do find myself waking up at 3 or 4 am, being alert for 30 minutes or so and then going back to sleep only to wake up a little groggy at 7 am (while it’s still dark outside).
    My desire to sleep, and sleep heavily at that, are strongest in the winter and I think that is why biphasic sleeping didn’t work for me then. The impact of natural sunlight must play a factor in this sort of sleeping pattern.

    Regardless, I’ll try out this test now that it’s summer and I feel like I don’t need that much sleep and I’ll see how I feel.

  35. I just thought I had middle of the night insomnia. I prefer it when my wakeful period is less than an hour, preferably less than 10 minutes and that is easier now I’m no longer worried about waking up. If I stay awake longer than I would like I just meditate and usually find I go back to sleep. In winter I like to be in bed by 9pm and up again around 7.00 or 7.30 ie dawn. In summer I go to bed around 10pm and can be up and walking the dog around 5am, and the less sleep doesn’t bother me then.
    Just as an aside. I sat in cold water last night before bed (can’t lie in it yet) and had a much deeper sleep than usual last night.

  36. I have always found this type of sleeping pattern to be natural, but whenever I mention it to anyone, they think I’m crazy. In the last couple of years since I started working 12-hour night shifts three times a week, this four-hour-sleep then another sleep of whatever length I need works great at keeping me from being worn out.

    Eat when you’re hungry, sleep when you’re tired. Of course real life intervenes, but just like everything else, do the best you can!

  37. (Off-topic)

    News Flash! Just in: Paleo diet hits the bigtime: now featured on page 20 of the June 18th issue of the authoritative medical journal “Woman’s World” (available at your grocery store checkout line).

  38. I remember on the farm I often did the biphasic sleep pattern out of necessity, whether it was because of calving season or the irrigation canals needed to be changed, it allowed me to get some sleep and I still felt good; I always chocked it up to the vigour of youth. I cannot see this pattern working in my world now, as much as it makes sense, being a nurse and having shifts around the clock would make this impossible for me and probably most shift workers.

  39. As a breastfeeding mom to a newborn, I find this already a natural part of my sleep pattern. However, I’m up multiple times with sleep in between rather than two blocks of sleep. I was listening to a podcast on Underground Wellness about sleep and the doctor in there mentioned that breastfeeding hormones allow for the mom to get up and down multiple times without getting too sleep deprived. Now I wonder if it has more to do with biphasic sleeping.

    Also, interesting to note, in the first month of breastfeeding a womans body produced prolactin to bring in the milk supply. This has the effect of making the mom feel drugged and drift off to sleep while breastfeeding. I’ve caught myself more than once jerking awake while nursing. At least it’s normal.

  40. Islam actually prescribes biphasic sleep by encouraging nighttime prayers, preferably made after some period of sleep, and finishing off with a mandatory dawn prayer. since most people fall back asleep after that, its biphasic

  41. I would really love to try this, as I think I could benefit from it. I don’t know how I can fit it in with my schedule, though. I have to leave for work by 7:45am, and don’t get home until 6:30pm. I figure I could do something like 830pm-1230pm, and 230-630pm… But it doesn’t exactly leave opportunities for spending time with family and friends.

    Any suggestions?

  42. I too notice I wake up after 3-4 hours of sleep. I also find it helpful to take about 30 minutes reading and meditating then going back to sleep.

  43. I naturally have this sleep pattern, and have had it on and off for years. Go to bed at 11pm, wake up for an hour around 3am, eventually get back to sleep and wake up again at 8am.

    The only good thing about this is that I start work later than most people, so I get in 8 hours. For the rest I never feel fully relaxed or rested. I’ve been paleo for 6 months and that has made no difference to this pattern.

    My N=1 experiment feedback – biphasic sleep sucks ass.

  44. I think I’ve done this by accident and felt great. Like when I get up and deal with overseas stuff online. I know jumping on the computer probably isn’t the best thing, but the idea of two phased sleep has worked in my favor in the past. I just didn’t know why.

  45. I switched to a Biphasic Sleep pattern a couple months ago and while I havent stuck to it 100% (I’m in NYC where life DOES happen at all hours) it has definitely changed the way I live.

    I used to fall asleep on the couch somewhere around 10pm, sleep poorly then go to bed later, getting between 5 and 7 hours of “bed sleep” afterwards. Now I take a 90 minute nap somewhere around 8 or 8:30, wake up refreshed an ready to go then get 3 more hours usually between 2 and 5 or 3 and 6 depending when I want to get up.

    This not only reduces the number of hours spent on sleep to 4.5 (sounds ridiculous right?) but I feel better rested all day, avoid my mid-afternoon slump (even without coffee) and ALL the time I am awake is more productive. I use my “Bonus Time” between sleeps for walking the dogs, housework, listening to coast2coast AM (guilty pleasure but its on from 1-4am for me so I rarely got to enjoy it otherwise), getting ahead on work for the next day or just reading and taking a break.

    Being able to skip a day or to drop it for a few days if necessary certainly makes it easier to adjust. If there is something going on, I just sleep in one block in multiples of the 90 minute cycle (6, 7.5 etc). If I am more tired than usual, I will extend one of the sleep periods by a cycle (3 and 3, 1.5 and 4.5 etc). I feel like it gives me the tools to get the optimal amount of sleep. Not too much, not too little.

    As far as Mark’s Metrics (I’m a Web Analytics consultant, data is a passion):
    Productivity – I am FAR more productive, especially given the additional time I can devote to work if necessary.
    General wakefulness – 9-10, depending on the time of day
    Grogginess – I actually feel more rested after my first (shorter) phase. at that point I wake up around 8-9 then level off higher.
    Recovery – Workouts are noticeably better when following biphasic sleep.
    Immune system – I am getting sick less often and my Seasonal Allergies are less severe

    I was a but surprised to see the sweeping generalizations in an earlier post (the MDA community is usually just so nice!). From a later response, it looks like the comments about programmers were tongue in cheek(?) but the lifehacker bit in the comments is ridiculous. Isn’t Paleo/Primal the biggest lifehack of all? Lifehacking is all about solving a problem in a non-standard way and even though Paleo/Primal living focuses on trying to mimic the way our ancestors did things, in today’s society it is far from “normal”.

    As with anything else (Paleo/Primal included) don’t knock it ’til you try it because you just may like it!

    Mark – Great post! It cant have been more than 2 weeks since I searched the site for your take on Biphasic Sleep and I’m glad to see your interest (even if cautious) and hear your take on the subject.

    1. I’m the one who slammed ‘Lifehackers’, so I guess I will respond. I admit I was using the term as it originally meant (a definite misnomer, if you ask me), i.e., little tricks busy software people use to speed up their workflow and ‘productivity’ (a term I detest).

      Mark and others use the term in its more recent meaning, apparently, having to do with tweaking parts of your lifestyle for personal betterment. I’m all for that. Sign me up. But I kinda reject the characterization of Primal or Paleo as a lifehack. It’s bigger than that, more of a paradigm shift. The Squatty Potty is a lifehack.

      Sometimes one has to turn things upside down to make things better, rather than tweaking one’s life to patterns that others have set. E.g., if your boss wants you to go on a rotating shift (a recipe for ill-health in many people), you might try to accomodate this by various lifehacks, but you would probably be better off getting a new job less dangerous to your health.

  46. I have been doing a modified version of this quite accidentally for about a year now. My body is quite happy on 10 hours of sleep, but with my 5AM wake up call, that would mean a 7PM bed time, and no time at all with my husband or family!

    I go to bed absolutely no later than 10 and get up at 5 to make breakfast, do morning chores and get the kids to their respective jobs. At about 10 in the morning, I settle in for a 90-minute nap. I wake up and make lunch and finish up the day without needing an afternoon “jolt” like I used to.

    I wondered if I was harming myself by not sleeping in one big chunk, or maybe messing with my calorie burn by napping. But, it works for me and my 8.5 hour biphasic sleep is as restful as a 10 hour chunk.

  47. I was able to do this for a few months several years ago and loved it! I had a part-time job that ended at 2 pm, so I’d come home and nap for a couple of hours. Then I’d get up and work on the arts I sold on the weekends at craft fairs until 1 or 2 am. It was a great way to get the right amount of rest, plus I have always been more creative late at night. It turned out to be the best of both worlds for me.

  48. How interesting. This happened to me last night. I’m dog sitting and one of them woke me up to go outside but then I couldn’t get back to bed. I was up for about 2 hours, spent the time worrying about getting back to sleep and getting enough and then got up about 3 hours later. I feel fine…

  49. Biphasic sleep sounds very interesting, I think I’ll give it a try.

  50. I like this concept, I have been napping everyday for awhile now and love it. I’ve been in a bad habit lately of going to bed around midnight because I’ve been watching the playoffs but when I used to go to bed around 9:30 p.m. I would naturally wake up around 4:00 a.m with tons of energy. I’d get up and maybe read a little and go back to sleep around 5:30 and sleep til 7:30 and I felt so refreshed doing this.

  51. This is amazing–so glad I read it. For the last 10 months, I have been dropping to sleep at 9:30 or 10; sleeping till 1 or 2, then awake till 3, and sleeping till 6:30. I thought something was wrong with me, yet I felt fine.I have had a higher level of stress, yet this has seemed to work. I wonder if people eating an American diet have this pattern, or it may also be to our paleolithic lifestyle just lends itself to this…………?

  52. I always wake up around 2:30 am. Every night. Get up to pee, lay back down. The mind is active. I meditate/pray for about 20 minutes and fall back to sleep to wake up with the birds and sunshine. I am glad this is normal and has a name! I thought I had just created a habit.(or had a small bladder..)
    Husband does the same and will often get up and do things for awhile. He did think it was a sleep problem. I can’t wait to read this article to him! As always, very informative. Thank you!

  53. My thoughts exactly, since going primal everything has changed for me.

    I get very tired around 6pm some nights, and could easily go to sleep.

    What would happen is I would wake around midnight, I’d get up, be lucid and alert and really motivated to do stuff.

    I felt guilty and stupid doing “stuff” in the night, and would force myself to GO TO BED.

    I would then sleep until about 9am if I wasn’t woken by my alarm at 7am.

    I am a sleepy head. I can function on 6hrs but only if it’s a once in a blue moon event. I usually get about 8hrs and feel tired. If I get 9-10 hours I feel like I could do anything…

    Breaking it into two blocks might reduce my sleep hours but leave me feeling refreshed?

    Something to consider…


  54. One of the most important variables determining how people sleep is the latitude where they live. People (and animals), generally at or above 45 degrees latitude, are greatly influenced by seasonable changes in daylight hours. At 50 degrees this time of year (of maximal daylight hours) naturally induces a long midday nap and less sleep at night. But in the winter around the end of December much longer sleep is required at night and a short midday nap . This is naturally the case with those people in tune with their environment at these latitudes – those who work outdoors, or spend most of their time outdoors.

  55. I also began waking after that first four hours, falling asleep and waking again 4 hours later. At first I was annoyed but when it didn’t affect my energy negatively for the day I just started going with it.

    There’s a great documentary on Netflix by Nova on dreams that I watched about a year ago. They did sleep experiments and found that we dream in both REM and non REM sleep and they are different types of dreams and equally important. Anybody interested in the lifehack option should watch it and then decide. If the lifehack completely eliminates time in nonREM, there may be unforeseen consequences.

  56. How is this going to work for those of us in the northern reaches? I’m only in Germany, and it is fully light at 4:30a.m. and sun goes down around 9:30p.m. That’s not enough time for your experiment, during the summer – plenty of opportunity in the winter, of course!

  57. This explains so much! I have always fallen asleep soundly for a brief period only to be fully awake in a short time. This can range anywhere from 15 minutes to 1-1/2 hours. I think the 15 minute variety is just leftover from my college days of dozing in the classroom.

    This “insomnia” is most prevalent in the summertime and the mention of shorter days made sense. In the winter, I don’t sleep like that at all.

    I talked to my physician about it and he was baffled because he thought if it were a seasonal disorder I would have trouble in the winter and offered pills, which I declined.

    This sleep pattern also runs in my family as my mother and grandmother had/have it as well.

    Now if I could only convince my wife she should wake up with me.

  58. I have a question for Mark, or anyone else that knows, regarding the modified biphasic schedule.

    I work 10 hour shifts and travel about 30 minutes each way to/from work. That gives rougly 11 hours between when I walk out the door and back in, which means about 11.5 hours from when I wake up to when I get home.

    Is it a hard and fast rule that you must be taking your 90 minute nap within 10 hours of initially waking up or can I adapt this plan to be a 90 minute nap 12 hours after my anchor sleep?

  59. How do I put myself on the 4,5 hour schedule? Do I just have to put an alarm, or are there other ways to wake myself?

  60. So my 20-year old daughter calls me at 1:30 a.m. to come get her from a party. While I’m glad she had the good sense to call for a ride, I’m tired and none too happy about being roused in the middle of the night. She says, “Mom, I’m just trying to help you with your biphasic sleeping!”

  61. OMG thank you for this article I feel like it explains a lot of what has been happening to me for the past couple of months! I have currently relocated from Sydney Australia to Scotland UK and thought i was going crazy! I have gone from someone who would sleep right though the night back home in OZ to someone who sleeps for 4hrs then wakes for about 2hrs then can sleep for another 3-5hrs again. Seeing it is summer here and also daylight savings it is light till 10pm and never really gets very dark like it would back in OZ then the sun starts rising again at 430am. So yes i have found my body has definitely synced with the sunrise/sunset. I will be interested to see what happens once winter comes…

  62. Hello All,

    I am an RPSGT which stands for Registered Poltysomnographic Technologist. A few years ago, I read quite a few well researched, well-regarded scientific publications on the science of sleep. I took a hard exam and made a good grade on it. As part of my job, I worked the night shift for years, so I have personal experience with alternative sleep habits.

    Put simply, polyphasic sleep is extremely bad for your body. There is no proof that humans ever lived the way they are portrayed in this post. There are many urban legends about Polyphasic–and being urban legends, impossible to prove true.

    Many people start ‘the experiment’ and then discontinue but are too ashamed to post the fact that they quit.

    Please, if you are interested in taking care of your body, do not choose to sleep in this manner.

    Thank you,

    A Concerned Citizen

  63. Ever since I took up amateur astronomy, I have found that sleeping from both 6-9 AM and PM fully refreshes me, and enables me to potentially be awake for 18 hours a day without ever feeling exhausted or tired(outside influences notwithstanding). After the week it took to adjust, I wonder why I ever slept any other way.

  64. I have been grounding during my sleep for past 4 months with noted dramatic improved quality of my sleep. Consequently I awaken at 2-3 am feeling great – the biphasic concept makes great sense and has given me ideas on how to use the remainder of my night and catch another block to finish off. Thanks for the ideas

  65. Mark, Thanks for all this information on sleeping/not sleeping/getting more sleep. This article has been a comfort to me since I (use to) stress about waking in the night and only getting a few hours of sleep. I may be on a biphasic natural. When I was younger I could sleep through anything, however, that went away around 40’s so it’s almost been 20 years this way. Some nights I can stay awake all night long. I finally quit stressing about it since I didn’t feel tired nor harmed the next day after “losing sleep” , shoulder shrug. I am going to look into blue blocking glasses and the thing for the PC though. I’m getting some yellow and red bulbs and trying to figure out what to do for the hours I’m awake. I can fall asleep at 8ish but try to stay awake until 10, if I fall asleep at 8 I’m awake at midnight for the rest of the day. Maybe I’ll read a bit and then go back to sleep? Still have to get up at 5 but maybe it can work. Wish I could just exercise during that time, no other time usually.
    Oh my, work is going late tonight! Need some blue blockers, ahahaha.

  66. Hi Mark and thank you for this article.

    I am doing Everyman for almost 10 months (Everyman with 2 naps). It was pretty hard to adapt and I still oversleep sometimes. I find your method with variables and measurement criteria very interesting.

    An important point for anyone who wants to do polyphasic sleeping: You absolutely need to be and stay motivated. So be clear with your goals and why you want to do that. For example, you should have one or several projects you want to complete thanks to biphasic sleep (or any other kind of polyphasic sleeping). Otherwise you will just have more time per day, be exhausted, have no project and you might feel depressed…

    I am launching a new site on biphasic/polyphasic sleep:

    I will add more articles and videos in the next few days and weeks, so check it out.

  67. Hey!

    I have something to say about the life-hack method. I was doing this practically all the time during highshool. And I am genetically predisposed to depression and anxiety, but I believe this contributed a lot towards developing the disorders. Not to mention, it was impractical- I was tired all the time during the day (and I believe adrenaline kept me going, I felt very alert and sort of drunk-like) and most alert at night. After I got under a lot of stress, I started sleep talking and I had numbers of sleep paralysis – these occurrences and bad sleep in general are linked to mental health problems. I did not know it at the time, but I was on my way to depression. Beware.

    I am going to use natural biphasic sleep for helping me to cure my severe life-crippling anxiety. To sum it up sleep is crucial, not for memory, concentration, but also for mood, creativity… Wish me luck!

  68. This is utter drivel. There is zero evidence that this was ever a normal sleep pattern. The historian who popularised it with cherry picked and decontextualised refs was doing it to ‘prove’ his preexisting modernity-hating thesis.

  69. i am a student i need to be active from 5am to 6am for physical exercise in morning and 7am in morning till 2pm in afteroon after lunch at 2pm i want a nap maybe from 3 pm to 4 then i need to be active from 4pm till 6pm for games and 6.30 to 7.30 study then after dinner at 7.30 from 8.30 i need to be active till 9.30 to study then sleep. i have heard that being awake for 2 hours in night goeas well with circadian rhythm…how can i adjust two hours in between night and morning in my circadian rhythm so i remain attentive until lunch……your help will be highly appreciated 😀 PS i am 16yrs and live in new delhi, india 😀