Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
23 Feb

Is “8 Uninterrupted Hours a Night” Flawed Conventional Wisdom?

sleepcycleConventional Wisdom always gets an eyebrow raise from me. I can’t help it. Eventually, I take an honest look at whatever the experts are saying, but skepticism gets first dibs. I’d call it an instinct if it weren’t learned behavior from years of being burned. For example, I once took to task the most pervasive “truth” around: that everyone needs to drink eight glasses of water a day or risk kidney failure, toxin buildup, bladder cancer, and debilitating constipation. It was pretty easy to do.

But it’s not all BS. Smoking is bad for you, for example. See? I can admit when they’re right!

I wonder about the CW position on sleep, though. We generally agree on the recommended duration of sleep. “About eight solid hours” is what you’ll see everywhere, from official governmental health guides to paleo nutrition blogs (I’m sure there’s some niche community out there claiming to have “transcended” sleep, though). I’m not going to argue with around eight hours, but note the use of “solid.” What does it connote?

Unbroken. Monophasic. Constant. Actually, it both connotes and denotes these things. Solid sleep is good sleep, right? And solid sleep means sleeping for about eight hours without waking. If you wake up, you’ve got a problem. Right?

Maybe not.

For most of human history, nighttime meant darkness. Not the blueish whitish permaglow from storefronts, billboards, and headlights enjoyed by modern city-goers. Not the yellow-orange bath radiating down from street lamps on quiet suburban streets, so ubiquitous that you only notice them when they go out. I’m talking about real, permeating darkness. Camping darkness. Small country road with the car lights out darkness. For our ancestors as recently as a couple hundred years ago, this kind of nighttime darkness lasted up to fourteen hours (well, it does today, too, but we mask it with all that lighting and housing). Artificial lighting meant candles and firewood, and those cost (money or time) and don’t really replace daylight (anyone who’s stifled yawns around a campfire knows that) like today’s artificial lighting replaces daylight. People got to bed earlier – because, unless you’re rich enough to burn candles all night, what else are you going to do when it’s dark everywhere but, as Thomas Middleton said, “sleepe, feed, and fart?” – and their sleep was biphasic, or broken up into two four hour segments, with the first beginning about two hours after nightfall.

The first segment of biphasic sleep was called “first sleep” or “deep sleep,” while the second was called “second sleep” or “morning sleep.” Numerous records of these terms persist throughout preindustrial European archival writings, while the concept of two sleeps is common in traditional cultures across the globe. Separating “first sleep” from “second sleep” was an “hour or more” of gentle activity and wakefulness. People generally didn’t spend this time online gaming or surfing the web or trolling the fridge for snacks; instead, they used it to pray, meditate, chat, or to simply just lie there and ruminate on life, the universe, and everything. It was still dark out so they tended to keep it pretty mellow. Sounds nice, huh?

Robert Louis Stevenson liked the idea, too. Sleep historian (awesome-sounding job!) Roger Ekirch writes of Stevenson who, in the fall of 1878, while trekking through the French highlands on foot, alone, made a remarkable discovery. As anyone who backpacks or spends time outdoors will corroborate, Stevenson found himself drifting off to sleep shortly after sunset. He awoke around midnight, smoked a cigarette, and, only after “enjoying an hour’s contemplation,” fell back asleep. That hour, that “one stirring hour” moved him; Stevenson had never before experienced a “more perfect hour.” He had awoken not because of an interloper, a night terror, or any other external actor, but because of what he later described as a “wakeful influence [that] goes abroad over the sleeping hemisphere” and is unknown to “those who dwell in houses.”

Ekirch thinks that the Industrial Revolution, especially the invention and proliferation of cheap electric lighting, forced modern society into its current monophasic sleep pattern by making artificial lighting that really lit up a room available to everyone. People with access to light bulbs could stay awake longer in brightly lit rooms because they were no longer subject to the circadian entrainment of natural light patterns. We’ve gone over light entrainment before. It’s likely worse nowadays, since we’re not just coping with access to ambient lighting, but also loads of interactive consumer electronics (like this laptop I’m using now) blasting circadian-disrupting light directly into our faces. Whereas Owen the London chimney sweep may have flicked on the light bulb and settled down to a good book and a bottle of ale after his shift and gotten to sleep around nine or ten, Jeff the SEO analyst stays up late arguing on Internet message boards with the laptops blue light beaming into his very soul. Sound familiar?

It’s likely that societal expectations about sleep structure – that it’s supposed to be eight hours of unbroken, deep, heavy slumber, as everyone knows – are making problems out of what may be normal sleeping patterns. Clinicians are finding that if they can make insomnia patients understand that waking up in the night is actually normal and natural, they feel better about their condition. Because they “perceive interrupted sleep as normal,” they stop stressing over waking and are able to get back to sleep more easily. Some forms of insomnia, in which people wake up in the middle of the night, might not actually be clinical conditions, but rather the manifestation of the natural human sleep cycle trying to assert itself. Insomnia may just be a problem of perception; if you look at your “problem” in a different light as explained by Ekirch, it disappears.

Imagine the possibilities if you could work just such an hour of free waking life into your sleep cycle! You wake up and, instead of exasperatingly checking the time, making a huge huff, and angrily grumbling and tossing and turning in a vain attempt to get back to sleep…

You vigorously and enthusiastically discuss last week’s post with your significant other (whose sleep schedule is also entrained to the biphasic cycle), thus stimulating your mind and supplying a steady rhythmic stimulus to your hip extensors.

You linger in twilight mindspace, that odd world between waking and sleeping that we rarely get to explore, and ponder dreams with a clarity that the 7 AM alarm for work simply doesn’t allow.

You light a candle and quietly read for an hour or so until sleep returns.

Sleep phase entrainment isn’t that easy, though. We do “dwell in houses.” We have by and large been sleeping monophasically for probably our entire lives. Our world is the product of the Industrial Revolution, for good and for bad, and so we must work with that reality. Candles at night will help, as will camping trips when possible, and limiting excessive late night computer exposure (or installing the ever-popular f.lux) is always a good move. You can try getting outdoor light exposure during the daytime – maybe go for that hike, that walk at lunch, or that outdoor workout.

But we’ve gone over that stuff before. It’s good, but it’s been done. In light of this new (old?) information about biphasic sleep patterns, perhaps the most effective change we can make is in our perception of sleep and waking. Make like those insomnia patients and change the way you think about waking up during the night. Don’t stress and fret; welcome it. Maybe, instead of assuming that this is all a horrible mistake and your cortisol is going to spike and you’re going to crave extra sugar in your coffee in the morning next time you wake up in the middle of the night, welcome it. Ever notice how you’re not all bleary eyed and zombie-like when you wake up at 2 AM like you are at 7 AM with the alarm blaring?

I’m thinking we should all explore why that is.

What are your experiences with waking up in the middle of the night? Do you need a solid block of sleep each night, or do you just assume that’s the case? After reading today’s post, see if your next mid-night wakeup feels different.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. You’re bang on when you say it’s all about perception … as soon as I even saw the title of your post I knew I had to read it, because there’s such a large part of me that feels I’m a failure for not sleeping the requisite 8 hours each night … sometimes it’s because I truly am staying up too late or pushing the morning alarm too far, but often (and even despite those things) I do feel great on less.

    Interestingly, as a former insomniac I never woke during the night but rather tossed and turned at the start of the night (often all night; usually until at least 3 or 4am) … but what I have noticed is that there have been the odd occasion when I wake during the night and then I get up and write and write and write – sometimes I might even think my best work!

    Perhaps if I started to view that sort of activity as normal or healthy it would actually ‘work’ for me … although I guess I should probably switch from writing on computer to journalling!

    Kat Eden wrote on February 23rd, 2011
  2. When my children were infants I never minded the middle of the night(2:00 – 3:00am)feedings. I always felt pretty good during that time and looked forward to that feeding. It was the 11:00 PM feedings that were the worst. I guess now I know why…

    Stacy wrote on February 23rd, 2011
  3. I remember a friend in high school telling us that she did this – she’d wake up at 2 or 3 in the morning and then do her homework before going back to bed. We all thought she was strange. :)

    I’ve always woken up in the middle of the night, sometimes for an hour or so and sometimes only briefly. Recently I’ve discovered that even on the nights when I thought I slept solidly, I didn’t: I’ll wake to find that my computer’s charger has been unplugged, wrapped neatly, and put away. When I then think about it, I’ll remember waking up and doing it.

    I definitely sleep better all-around, biphasic or monophasic, without the excess carbs and sugar.

    Renee wrote on February 23rd, 2011
  4. My perception has now changed on how I “should” be sleeping. Next time I wake in the middle of the night I will try to use that power hour instead of laying around thinking when I will get back to the zzz’s.

    FlyKev wrote on February 23rd, 2011
  5. I’m a teacher with a little boy at home, so I start my school work when he goes to bed. I’m often up very late, and average 4 hours of sleep a night. I find that getting more sleep than that actually makes me feel worse in the morning. Six hours of sleep just kills me. Recently, my son has been sick and I’ve woken between 1 and 3 AM to his coughing. I thought it strange that I felt refreshed and wide awake then, but struggled to get out of bed just a few hours later.

    Mark, for someone like me, would my first and second sleep be divided into just two hours, or have I “worked through” my first sleep by going to bed so late? What effect does REM sleep have on the biphasic sleep theory?

    ioelus wrote on February 23rd, 2011
  6. I live with the spirit of a man who has learned to communicate with me using a certain type of nightlight, which he sets off by himself. It’s very pretty, actually. I have these lights all over my studio, and typically I fall asleep to them in my recliner.

    I usually wake at some point during the night, have a little “chat” with my ghost friend (who is always wide awake at night), maybe meditate a little, then go down the hall and get into bed with my boyfriend. The whole thing is very weird, but oddly soothing. I’m quite used to it by now.

    I sleep much better since I work at home now, and don’t have anywhere to go in the morning. So waking up at night is quite enjoyable. I love how quiet it is when everyone else is asleep.

    Anna Barlowe wrote on February 23rd, 2011
  7. Maybe the nightly wake up is part of our cave man genetic heritage. We generally accept that we can’t handle a lot of carbs because our genes haven’t evolved enough. Don’t forget that we also were exposed to predators when we slept. Perhaps we evolved so that a 4 hour window of first sleep was optimal for our survival. Any sleep that we got after that was just gravy . . .

    Joe wrote on February 23rd, 2011
  8. i wake up every single night at between 2 and 3 normally, no exceptions. i pee, crawl back in bed, and usually fall back asleep within 20 minutes. this has been how i’ve lived my entire 40 years. to me, biphasic sleep is simply a pee break.

    chrissy wrote on February 23rd, 2011
    • Me too! My husband makes fun of my 80 year old bladder (while the rest of me is 24), but now I know he’s the weirdo for being dead to the world for 8 straight hours.

      We just got a puppy who recently started sleeping on our floor (b/c although waking up once may be normal, staying awake for 2 hours listening to barking multiple times a night is NOT). He sits in the bathroom while I do my thing, then I take him out to do his thing. It’s our bonding time:)

      Alex wrote on February 24th, 2011
  9. Very interesting article, thanks Mark!

    What about polar nights and days? I’m curious to hear how my ancestors fit your darkness theory… I was born above the Arctic Circle and for a couple of months a year, we don’t get any darkness at all (and the opposite).

    Miss Glamourpuss wrote on February 23rd, 2011
  10. Now i know why i ALWAYS wake up when camping, guess i shouldn’t feel so bad about having to get up and stoke the fire before dawn.

    Ardent wrote on February 23rd, 2011
  11. What about afternoon sleep? I can sleep pretty solid (I think) 8 or 9 hours a night but I’m never really refreshed until I had a ~20 min afternoon nap. My sleepiness progressively worsens until 4 or 5 pm when I go, if I can afford, to sleep. This is ok, but a) I don’t understand why and b) it’s not always work/social friendly.

    Raj wrote on February 23rd, 2011
  12. This is fascinating stuff!

    Incidentally, in the transportation field we are well aware that “8 hours of sleep” is actually two 4 hour chunks. In fact, in the railroad industry, the employer is allowed to schedule you such that you get two 4-hour periods in a 24 hour period. We hold no illusions that this is optimal for alertness–it’s more of a bare minimum standard–but it’s based on scientific studies of sleep and alertness that showed that it is well into a 2-3 hour stretch that the body enters into the healing deep sleep phase. (4 hours uninterrupted lets you stay there for 1-2 hrs.) The sleeper then ‘surfaces’ at the end of the 4 hour period. So it is not surprising that someone who went to sleep early (naturally, because of darkness) might entirely wake up for a while on their own. Even people who do not consciously wake up surface to a very light sleep level when the deep sleep cycle completes.

    Just as a side note, I think the regulations for commercial drivers and RR workers still need some work. CDL drivers are given EXACTLY 8 hours off as legal minimum. Unless you report to your car and sleep in your clothing, you actually have to: commute, eat, put the kids/dog to bed (or whatever), fall asleep, wake up early, bathe, dress, commute. How many hours of sleep does that leave you?! But I have known a number of drivers who made it a habit to sleep 4 hours during long split shifts*, giving them plenty of active hours during their mandatory 8 hours off. :D

    *A split shift is just what it sounds like–a number of hours on, a number of hours off, a number of hours on. Let’s say you are a 40-hour/wk (full time) employee. You might work 5:30am-9:30am and return to work 3pm-7pm, for a total of 8 hrs in a 13.5hr period. There are also part-time split shifts, with each piece being 2-3 hours each (typical for school bus drivers).

    Another Halocene Human wrote on February 23rd, 2011
  13. Also–did anyone else read this and think of “The Night Before Christmas”? How about the witching hour?

    Another Halocene Human wrote on February 23rd, 2011
  14. I think the answer is pretty obvious – do what’s right for you personally. If you feel good with 8 hours then do that. There’s no right answer for everybody.

    John wrote on February 23rd, 2011
  15. We have never enforced bedtimes or any rules around sleeping with regard to our children and, as a result, all three reflect this biphasic sleep pattern. Especially my youngest … he will fall asleep within a couple hours of sundown, no matter where or what he is in the middle of, and wakes up during the very early morning hours (2-3am) every night. He is never awake for long, but if he isn’t already in bed with me, he will find his way into my bed, if he is, he adjusts, wakes me up with a request to snuggle. And he is almost always first up in the morning, right with the sun. I am glad to know that I don’t need to stress about the 12 years of interrupted sleep I have experienced since having children … they are just keeping me primal! Amazing how primally tapped in our children can be when they don’t have standards of conventional wisdom forced on them.

    Cathy wrote on February 23rd, 2011
  16. DH & I regularly have “slumber parties” where we wake up & cuddle & talk for an hour–usually around 3-4 am. We get really good sleep when this happens!

    Sondra Rose wrote on February 23rd, 2011
  17. Great post! Very thought provoking.

    I nurse my 14 month old who goes down at 8pm, wakes up a 12:30 and 4:30 to nurse like clockwork, then sleeps until 6:30-7. It works out great for both of us! It’s nice to have reassurance that this way of sleeping is normal to the human condition.

    Kim C. wrote on February 23rd, 2011
  18. This is definitely eye opening. I am one where I wake in the middle of the night, but am wide awake, but I cannot wakeup, for the life of me, in the morning.

    Kevin Raymond wrote on February 23rd, 2011
  19. Huh, isn’t it interesting that having someone tell you it’s ok makes it ok! I used to think I was awake so I’d just get up and go off to the gym at 4:30AM

    ottercat wrote on February 23rd, 2011
  20. For years and years I have awakened every night several times. When I had to be at work by 4 AM, I would stress out about it and be a clock watcher. Actually blamed my job’s hours about my sleep quality.

    15 years later, without that job, I found that over the years I awaken less times during the night and don’t panic about it and have learned to enjoy that time for day dreaming, thinking, planning. Direct correlation? I think so.

    In fact I have friends who take sleep meds and when they still can’t sleep “through” the night, I suggest they just accept it and go with the flow, so to speak. They can’t believe that I am so rested with my “interrupted” sleep pattern. May have to send this article to them.

    I also enjoyed the late night feedings of my three babies……so stress free, no demands and totally connecting with the wee one.

    I like to sleep outdoors during the summer on the patio overlooking my backyard and water feature (something I planned during my awake times.) I usually get up at least once and sometimes walk around my yard and in the morning, laying there, watching the sun come up and the birds and animals is so peaceful. Great start to my day!

    Thank you again, Mark, for confirming what my body already knew.

    Dragonfly wrote on February 23rd, 2011
  21. I have been using a Fitbit to monitor my walking and it also monitors my sleeping too. I found I have A lot of active times in my sleep period. one of my kids who never seems to sleep like me has a similar pattern.
    Being out of work has let me sleep on my time more often, and I know I tend to fall asleep with darkness and wake with sunrise, even if the room is blacked out. But I also know I have waking periods where I have to do something or sometimes need food. I often avoid reading as I then dont stop until I finish book or have to do other things.
    My husband sleeps like the dead and two of my kids also tend sleep all night too, so some of us are probably pogrammed to sleep longer stretches some are not.
    I do have a preference for dark rooms for sleeping or moonlight/starlight options.
    I do like using the Fitbit to monitor my sleep habits so I can also see how drinking a couple glasses of wine, or certain medication is affecting my sleep activity besides just knowing about my waking periods etc. Also since I journal or note my waking moments can compare my notice of waking moments or dream recalls with the sleep activity. I apparently toss a lot in my sleep lol.

    Tamara wrote on February 23rd, 2011
  22. Whenever I’m sleeping outside by a fire, I always wake up to feed the fire and I fall back asleep so easily. If you think about how our ancestors slept, it would be very rare to get 8 hours of sleep. The fear of predators probably kept some people awake, like the sound of a lion. But with a fire it really adds moral and elimenates most fear. And of course through-out the day we would take naps whenever we felt like it. It’s not like we had much else to do lol.

    Andy wrote on February 23rd, 2011
  23. Thank you so much for posting this! All my life I have suffered from waking up in the middle of the night. Thinking this is a huge problem, I would get upset and have trouble getting back to sleep. Now, I can just happily wake up and do something relaxing for an hour and go back to sleep. Mark you are so right, realizing this isn’t a problem actually has me looking forward to my free hour tonight!!

    Gabrielle wrote on February 23rd, 2011
  24. Wow, thanks Mark. I needed this. For years I have not been able to sleep more than four hours without waking up and not being able to get back to sleep for 1-2+ hours. I would love to be able to get up during that time (not to have a cigar) but it would wake everyone else up. Instead I get stressed just lying there thinking “why can I not just sleep through the night like everyone else?”. I usually end up that stressed it can take 3 hours before I fall back to sleep and then I get up the next morning feeling very tired. I have been working on the theory that I suffer insomnia and that I need solid sleep. The fact that I have not been getting it has been increasing my stress levels. Unfortunately, my husband does not like to be woken up in the middle of the night, so I am on my own when I do, but I think I might just see what happens with a change in attitude. I will try something different tonight when I wake up, instead of stressing about not being asleep!

    Kitty wrote on February 23rd, 2011
  25. This makes sense because the second sleep in the mourning feels so deep and primal. this will definitely change the way I sleep.

    New commercial funded by pfizer : Do you have trouble sleeping though the night ? thats fine there is nothing wrong with you. just kidding you need powerful chemicals.

    Alex wrote on February 23rd, 2011
  26. I for one know that I fall into the `stress out when I wake up in the middle of the night` category. Nice to hear a fresh perspective and re-examine my own thought patterns. Thanks Mark.

    Matthew Myers wrote on February 23rd, 2011
  27. Another option is shorter duration night time sleep, with one or more short-duration naps during the day. There is some interesting data out there.

    “Problem napping and disruptive behaviors were also associated with longer nighttime sleep, shorter nap durations, and later rise times”
    http://brn.sagepub.com/content/9/3/244.abstract

    Lojasmo wrote on February 23rd, 2011
  28. Mark (or anyone) –

    What are your thoughts on eating in the middle of the night, in between these 2 phases of sleep?

    I’ve self diagnosed myself with NES (Nocturnal eating syndrome), whereby I wake up in the middle of the night and “need” to eat. It’s bad enough where I plan, precook, and have meals ready for this (otherwise I’ll probably binge on something less-than-primal).

    Anyway, just wondering if eating in the middle of the night is considered…bad?

    Thanks!

    Evan wrote on February 23rd, 2011
    • Evan, I used to have night hunger all the time. Like seriously, ALL THE TIME. Since I stopped eating grains and upped my protein and veggie intake, I rarely have the issue anymore. I think it’s a blood sugar issue, and that I actually have the same symptoms – feeling hot and sweaty, shaking, and having racing thoughts – during the day when I have a blood sugar crash too, I just don’t notice it in the same way. How long have you been on the PB? I’d be interested to know if your NES goes away as you get your blood sugar stable.

      Maggie wrote on February 23rd, 2011
      • Maggie, Appreciate the reply! I’ve been on the PB for, I believe 14+ months now. Started off pretty strict VLC, then relaxed and added carbs here and there.

        Ummm, the NES thing is weird, sometimes it hits hard, sometimes I do get an 8 hour uninterrupted sleep. Started in college (would wake up sweating and needed to cooldown so I ate icecream or drank a cold liquid).

        Typically though, I’ll fall asleep then wake up 1-3 hours later then HAVE to eat. Uncontrollable urge. Been trying out all types of “tools” – IF, VLC, Leangains…

        Do you eat VLC now? I’m wondering if its because I eat semi large meals prior to bed…? (1st meal for me is usually ~ 6-8pm).

        Evan wrote on February 24th, 2011
    • I am contemplating eating something during the middle of the night as well. If I am going to be wide awake at 2am, I may as well enjoy myself. I do find that if I have something to eat it is easier to go back to sleep afterwards. For me it is not a matter of being very hungry, and I have been 100% primal for about 8 months now (so I don’t think it is a blood sugar issue). I think a primal snack should be okay. I would like to hear Mark’s view on primal snacks in the middle of the night though.

      Kitty wrote on February 23rd, 2011
    • Mark,

      have you tried having your dinner shortly before you go to bed? I feed my hunger at around 9-10 PM and if I have a few strips of bacon or something on top of my meal, I can easily IF until AM next day. Never really “had to” eat in the middle of the night though.

      Tomas wrote on February 24th, 2011
      • ooops, you’re Evan, not Mark
        sorry

        Tomas wrote on February 24th, 2011
      • Tomas – Actually yes…I typically IF from whenever I last eat at night (usually 3am or so) until 6-8pm the next day. No hunger pains at all, no crashes, no mental fog, perfectly fine. Work out fasted, performance seems good day in and day out.

        Evan wrote on February 24th, 2011
  29. Maybe it’s not one or the other? Sometimes I can do just fine on 5 or 6 hours of sleep, but lately I have found that I feel most rested, most tolerant (I work with pre-schoolers, hello!) and most happy when I get 9 hours of sleep a night. However, I can’t do it every night. I’m starting to follow my rhythm more closely, and one thing above all else has helped me do that: turning off the technology. Seriously. I have realized that watching TV at night makes me completely unaware of my body’s signals. I can watch it till midnight and not feel tired, whereas when the TV’s off I notice that my body naturally starts to feel tired around 9-10pm. Interesting, right?

    Maggie wrote on February 23rd, 2011
  30. I think this is a very appropriate post. I was a sleepwalker as a kid, and I still talk (work) in my sleep if I am super stressed out. I will awaken tired and groggy if I have been “working” in my sleep. Otherwise, I sleep like a rock, and have always.
    Nowadays, I will frequently enjoy a glass or two of wine before bed, and this seems to surpress the “night talking”
    On the rare occasions that I wake during the night, due to hubby’s snoring, or a child in need of comforting,(slept with my nursing babies, so precious!)I don’t feel any worse off in the morning!
    My Mom is well into “the change” right now, and is plagued by insomnia..although she was always up in the middle of the night, perhaps I should forward this post to her!

    juliemama wrote on February 23rd, 2011
  31. I have always wondered why ship’s watches were set in 4 hour increments traditionally. Sailing is steeped in tradition from the days of tall ships, and this sheds some light on it. Sleep blocks of 4 hours would follow a natural circadian rhythm considering there is nothing but starlight, moonlight, and a smoking lamp out at sea.

    I personally have some serious issues to work through with my sleep, but this is some great info to take in! Thank you Mark.

    Mike Fout wrote on February 23rd, 2011
    • “I have always wondered why ship’s watches were set in 4 hour increments traditionally”.

      They weren’t, usually. There were three four hour watches and two six hour ones each day (and night). The longer night watch allowed sailors enough sleep to avoid sleep debt building up, and the longer day one allowed them personal time for things over and above necessities like getting a meal, washing, maintaining their own kit, etc.

      Also, as there were five watches in all, and that is a prime number, any breakdown of the crew into fewer sets was coprime to that and they would all cycle through every watch and get the watches they needed – which might not happen with six four hour watches. If a ship only had enough able bodied sailors to do watch on/watch off, everybody cycled through every watch every two days – a sustainable pace with that pattern.

      P.M.Lawrence wrote on February 23rd, 2011
      • Looking over that, I see that it might be misleading as I wasn’t specific enough. Formally, under the system that got standardised, the longer watches were actually two watches – an ordinary one run into a shorter, two hour “dog watch”, with the two dog watches back to back. The crew would only sometimes run the five watch pattern in practice by running an ordinary watch and a dog watch together, when they were so short handed that they had to do watch and watch – two sets of sailors, alternating – but not overworked by a six hour watch. When there were more sailors, or a different and heavier workload so that six hours without a break was too much (like “rounding the Horn”!), it was more practical to work the dog watches separately (making seven distinct watches, so the prime number thing still applied). But the five watch system matches sleep needs better if you can’t get a dog watch off next to another one, and was probably the first pattern historically.

        By the way, originally “watch” meant “stay awake”.

        P.M.Lawrence wrote on February 24th, 2011
        • Wow! That’s super cool info… thanks so much for posting this, P.M.

          Sea wrote on June 10th, 2011
  32. I spent two years trying to fight insomnia. We have two toddlers who enjoyed middle of the night talking, playing, crying, etc. It was ugly. Friends asked often if I were ok because my eyes were red? My wife (who works from home) never truly appreciated it until things got better (we got a king-sized bed and the kids’ sleep stablized).

    During that time, I started researching biphasal sleep. Taking an afterwork nap (I’m a school teacher) and embracing the the 90-minute blocks of deep sleep helped. I know now that 4.5 or six hours of nighttime sleep will be good. Now, if I can just get up when I wake at 4a.m. and do some writing or go for a swim instead of laying there thinking after I pee, I can get two more hours….

    Julian wrote on February 23rd, 2011
    • Maybe I’m missing something but, if you are on watch for four hours you must stay awake, correct? Thus leaving you the other 20 hours of the day for other duties and sleeping. So isn’t this point irrelevant?

      browntown wrote on March 14th, 2011
      • You are missing something. Ship’s watches didn’t mean that each crew member just got one watch on duty out of the whole day, unless it was the very unusual situation of a vastly over-manned ship (in which case, it was very important to find work for them to avoid problems from idle hands breeding discontent). Rather, the crew was divided into watches to ensure full coverage with sustainable patterns of breaks, which meant each sailor was on duty for several watches during each day. If the ship was short-handed (from illness and casualties, say), that might even mean “watch and watch”, i.e. each sailor was on duty every other watch and only got short breaks.

        P.M.Lawrence wrote on March 14th, 2011
  33. I used to sleep like a baby and never wake up. I felt fantastic when I awoke in the morning to begin my day.

    Recently I have been waking up in the middle of the night. I am not sure why but instead of becoming frustrated over this fact I am now going to welcome it. I feel awake when I do get up before I officially get up so maybe I should get up and do something for a short period of time.

    Thanks for this post Mark!

    Primal Toad wrote on February 23rd, 2011
  34. I have a two year old, so I haven’t had an uninterrupted night of sleep in about three years. What I wouldn’t give for a full eight hours!

    Seriously, though, during the last several months I have been waking at two a.m. Wide awake and alert. While this frustrates me to no end (read: huff and puff and pull the covers over my head while trying desperately to regain some shuteye), this post gave me pause. Indeed, perhaps my much-needed quiet hour of “me” time is coming in the middle of the night? This will really be good food for thought. Probably at two a.m. tonight. =)

    Dawn wrote on February 23rd, 2011
  35. My “normal” sleep pattern without fail involves peeing at least once/night, usually after a period of approx 1-2 REM cycles. Sometimes this pattern repeats. It’s rare for me to NOT do this, and I’m usually well-rested in the AM barring some other strange situation.

    Dawn wrote on February 23rd, 2011
  36. Our kids are 8, 5, & 2. No way in hell I’m getting 8 hours a night. More like 6 that is broken up. Good times. Can’t wait for them to grow up so I can sleep outside by the fire. :D

    Kevin wrote on February 23rd, 2011
    • :D Those were the days. I used to curl up on a large sheepskin rug in front of the fire for afternoon naps.

      Kitty wrote on February 23rd, 2011
  37. This could explain why my oldest son (8) gets up in the middle of the night, eats, watches alittle tv (sometimes skips this step) and then falls asleep on the couch. He’s always well rested and ready to go at 5 or 6 am.

    Casey wrote on February 23rd, 2011
  38. This winter I’ve been stuck working overnight security, midnight to 8am, and at the beginning it was absolute murder. I’d sleep from 9 to 4 and never get to see sunlight. I was depressed, had no energy, no appetite, it was awful. Now I sleep from 9am-12pm and go back to bed in the early evening when the sun sets (around 4 or 5). I only get 6-7 hours of sleep each day, but I have more energy than I’ve ever had in my life. It was amazing to find how natural two periods of sleep each day feels.

    Dan wrote on February 23rd, 2011
  39. You may have mentioned this previously, but I’ve been using F.lux (http://stereopsis.com/flux/) for a few months, and I *do* now find I slip more easily into sleep after shutting down my HAL-9000.

    On the subject of late night light pollution, is it just my crotchety imagination as a child of the ’70s, or are supermarkets and drugstores now *much* brighter than they were 15-20 years ago? I practically feel I’m having an “I’m coming home, Uncle Eddie!” NDE every time I shop for food at 12AM…

    Danny wrote on February 23rd, 2011
  40. Does anyone have any thoughts to helping with night time hypoglycemia and night sweats? Despite the excellent post from Mark, when you know your adrenals are shot and are being woken up by blood sugar drops/adrenaline release/vivid dreams, it’s hard to feel ‘serene’ during the waking hours.

    This is despite a low carb diet, around 50-60g a day, mainly from squash, carrots and beets with plenty of protein and fat split into regular meals. Digestion doesn’t handle heavier starch at all.

    Matt wrote on February 24th, 2011
    • Stop stressing your adrenals. Stressors could include: extended low-carb, overexercising, fasting, caffeine, alcohol, job you hate. I healed my adrenals and stopped the nighttime adrenal release by taking adaptogens, eating more carbs, and quitting coffee/alcohol and exercise for at least 6 months. I also quit my job and eventually got a new one. It worked!

      Gazelle wrote on February 24th, 2011
      • @Gazelle. Which adaptogens worked for you? I am currently reducing my stress load as well but my adrenals need that little extra help. I am at university though, and don’t want to quit that. I plan on taking a 6-12 month vacation when I graduate in order to get my adrenals completely healed.

        Kitty wrote on February 24th, 2011
        • I took something called AdreCor which has C and B vitamins and a few amino acids plus rhodiola rosea extract.

          Gazelle wrote on February 24th, 2011
      • Thanks Gazelle,

        The more carbs I add even at these levels results in a worsening of hypoglycemia.

        So I have a choice between low carb general adrenaline stress or added carb hypoglycemic stress. A nice choice to be faced with!

        But your probably right, it ultimately all comes down the adrenals I imagine.

        Matt wrote on February 24th, 2011

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