Why Seven Hours of Sleep Might Be Better Than Eight | Hacker News Reader

Why Seven Hours of Sleep Might Be Better Than Eight

online.wsj.com

88 pointspetethomas81 comments

> And getting too much sleep—not just too little of it—is associated with health problems including diabetes, obesity and cardiovascular disease and with higher rates of death, studies show

I don't understand how people can honestly report stuff like this. If you are sick, you often sleep more because you are drained and tired. That's plenty to make the data look like that. Sleeping more doesn't necessarily make you sick in the first place. There's no point bringing this up because it would be silly to try to sleep less to improve your health.

I don't understand how people can think scientists don't know this. From the article:

People who reported they slept 6.5 to 7.4 hours had a lower mortality rate than those with shorter or longer sleep. The study, published in the Archives of General Psychiatry in 2002, controlled for 32 health factors, including medications.

Of course controlling for confounders does not magically mean their study is perfect - there are always confounders that are either unknown or unable to be measured, particularly in retrospective/observational studies like this. But it's not nothing.

I think it's somewhat hard to necessarily point to the direction of association pointing the way the paper asserts its pointing, even leaving

I would have been much more impressed by using sleep as a time-varying exposure, rather than a time-fixed exposure, but the study is a rather old one.

Lumping all reports from 9.5 to 16.5 hours makes me a little nervous however - that's a range from "sleeps more than average" to "sleeps the vast majority of the day, and enough that a full time job is impossible". I'd assert those are very different people.

correlation does not equal causation.

Posting those 5 words doesn't dismiss an argument. You could throw out a lot of medical studies on that rule alone.

>>Posting those 5 words doesn't dismiss an argument. While it doesn't equal causation, it's a sure as hell cue that's something funny might be going on.

It may be a cue, but cues themselves are not actionable. They simply mean that more research is needed until causation is found.

If you look you'll see he edited his post to say something different after your response.

The dishonesty itself is astounding and I wish people had more pride in themselves than that.

This article definitely has some issues.

It should really be titled "For some people, seven hours of sleep might be better than eight", but that's probably not eye-catching enough.

The article supports what you are saying here:

> Other experts caution against studies showing ill effects from too much sleep. Illness may cause someone to sleep or spend more time in bed, these experts say.

There's this gem of wisdom only towards the end of the article:

> "I don't think you can overdose on healthy sleep. When you get enough sleep your body will wake you up," said Safwan Badr, chief of the division of pulmonary, critical care and sleep medicine at Wayne State University School of Medicine in Detroit.

Sleeping until you naturally wake up is generally a good strategy.

> Sleeping until you naturally wake up is generally a good strategy.

That sounds nice but doesn't fit my experience at all. If I'm in a dark room I can sleep 10-12-14 hours easily.

When my body wakes me up is not at all connected to how much sleep I need. Or certainly not directly connected.

>Sleeping until you naturally wake up is generally a good strategy.

WHAT? No no this is outrageous. This doesn't sound right. It needs to be a nice round number like 8. Yeah 8 sounds good.

It's not just the result of poor health causing more sleep. Both can be caused by a third factor. Chronic lack of exercise causes people to sleep 9+ hours per day. Put those same people on regular aerobic exercise regimes, and they start sleeping <8 hours.

Also, it's not the most outrageous hypothesis that oversleeping directly causes health problems, too. The body is complicated and poorly understood.

... Chronic lack of exercise causes people to sleep 9+ hours per day. Put those same people on regular aerobic exercise regimes, and they start sleeping <8 hours.

Peak performance exercise can demand 9+ hours of sleep. I'd be reluctant to categorize sleep needs based on exercise regime.

> I'd be reluctant to categorize sleep needs based on exercise regime.

You literally just did that.

Yep. Should have expressed that it is non-linear.

"Chronic lack of exercise causes people to sleep 9+ hours per day."

Citation needed.

Sorry, but personal experiences. Not the night of, of course, but having a habit of regular exercise.

I'm not sure of your issue. The article used the term "associated" meaning that the above average sleep could be a symptom and/or a cause of those referenced health problems. The article does a good job of identifying the optimal sleep duration of a healthy individual. (Healthy being free of temporary and permanent ailments.)

It's also silly to assume that a magic # is right for most people.

but if you wake up like a zombie, It is unlikely that you go exercise or cook something healthy.

The solution for me -- believe it or not, call me crazy -- it to go to sleep when I'm feeling sleepy and tired. I tend to read in bed; at least an hour before I want to actually sleep, I'll read. Sometimes I get to the point where I can't keep my eyes open after 30 mins in which case I pack away the book or kindle and go to sleep. Sometimes I read a bit longer than the prescribed one hour until I get to the point where I'm sleepy enough to go to sleep.

End result? I'm never tired in the mornings and I often wake up naturally before my alarm clock rings. I also don't have massive "crash and burn" effects on the weekends where I sleep for much, much longer.

You are far from crazy, it's just the opposite - you're doing exactely as one should. For (very) detailed explanation I warmly recommend "Good sleep, good learning, good life" [0] by dr Piotr Wozniak.

[0] http://www.supermemo.com/articles/sleep.htm

Depends on the book, sometimes I just keep reading and reading until the sun starts rising. I force myself to put down the book and try to sleep at least an hour or 2.

The key here is reading a book rather than your phone, laptop or some other bright screen which would stimulate your mind and prevent you from feeling sleepy.

I find that when I do this the only time I have trouble getting out of bed is when I know there is something I don't want to do on my schedule.

I often do the same though I have found different lighting levels to help set myself into a "preparing for sleep state". I try to mirror the same settings I would use if reading a paper book, even when reading on iPad.

Ceiling lights on, bed made: awake time.

Nightstand light on, 2 pillows propped again headboard to lay/sit up more: reading time.

Lights off, 1 pillow: sleep time.

This works for me when I am on vacation or moving a lot, instead of looking at my computer for 9+ hours.

But most of my days fall in the latter category, and if I stay up until I am tired, I end up sleeping every ~26h or so, and that ends up being troublesome quite quickly :(

"Sometimes I get to the point where I can't keep my eyes open after 30 mins in which case I pack away the book or kindle and go to sleep. "

Agree and I would add that an excellent way that I have found to get back to sleep (if you wake up in the middle of the night) is to do something similar. Although there are many things that say otherwise, I actually find that I can pull out the iphone, read for 30 to 40 minutes (even with the bright light) and I will fall back to sleep for the rest of the night. (In other words when laying there for 5 or 10 minutes doesn't do the trick.)

If I do that, I sometimes will just stay awake all night and not fall asleep at all. Very frustrating how hard I always find it to fall asleep.

Me, too. Worse, when I go to sleep "naturally", the best case is that I don't fall asleep at all and zombie the next day.

The worst case is that I do fall asleep, but wake up broken in some way: usually, it's cranial misalignment which gives me a massive headache the entire day.

you fool! If you don't get the exact prescribed amount of sleep down to the minute, you're going to die a day early.

I didn't read the study (just the article), but it appears that the authors are reporting their results for the "average" person. From what people say on here, it seems to me that sleep requirements vary a lot on a per person basis, and what works well for one person may not work well for another.

People have different health conditions, different amounts of exercise per day, different ages -- all kinds of factors. It seems that coming up with one number for everyone is far too simplistic.

For me personally, I feel absolutely horrible on anything less than 9 hours. I slept 7 last night and have been groggy all morning, even with 400 mg of caffeine. Part of my problem is that I got mono last year, and ever since then I've just been groggy in general. I asked my doctor about modafinil (which is supposed to keep you awake), but he said it had a high abuse potential and recommended corticosteroids instead. Meh, I'd rather have modafinil than steroids, so I passed on the offer.

I'm at a conference all this week, and it's quite annoying being "that guy" whose head is constantly bobbing during presentations even with sufficient sleep. No amount of rest seems sufficient to eliminate my tendency to fall asleep during lectures.

A sleep study might be a really good thing to do. Sleep disorders are very underdiagnosed, and many are identified only from sleep study results. Many many people with sleep disorders are completely unaware, and often go years before being properly diagnosed, if at all.

Personally i've been diagnosed with narcolepsy, but it took 9-10 years of problems and my life falling apart before any doctor caught it (finally having insurance thanks to the ACA). Modafinil helps me to be a little more functional during the day, and i'm really grateful for that.

Frequent dozing, microsleeps, like you're experiencing, even after a full nights sleep, are indicative that there is an issue here worth investigating.

I had mono during my university years and the need for more sleep stayed with me for several years after recovery. I managed to scale it back to a normal eight hour night by simply going to bed earlier, say 9-9:30 pm. The earlier I went to bed, the higher the quality of sleep and consequently the less I seemed to need.

I still go to bed relatively early compared to most people, around 9:30-10 pm, but I get up at 6 am and feel great. Give it a try and see if it works.

From the article, "'The problem with these studies is that they give you good information about association but not causation,' said Timothy Morgenthaler, president of the American Academy of Sleep Medicine, which represents sleep doctors and researchers, and a professor of medicine at the Mayo Clinic Center for Sleep Medicine." Yep. It's painfully difficult and expensive to conduct a good randomized treatment-control study of sleep duration with an adequate sample size for figuring out what is optimal as a population central tendency. I think the observation that many people put in a quiet, dark room in daylight hours will fall asleep is one hint that more Americans get too little sleep than too much sleep at night, but there is still more research needed.

When I used to live in the subtropical zone of Taiwan (the latitude of Taipei is about like the latitude of Miami, and the climate is not greatly different), there was still a fairly strongly established cultural custom of taking a nap, a siesta, after lunch. It look me a long time to get used to doing that, but it seemed to make sense, especially in the summer. Sleep patterns vary somewhat by culture and by climate, but the big influence on sleep patterns in the twenty-first century appears to be artificial indoor light, which is much brighter and much less expensive compared to average wages all over the world than it used to be. I always encourage people with sleep problems to get outdoors IN THE MORNING DAYLIGHT for moderate exercise to entrain their bodies' biological clocks. Behavior genetic research shows that the biological clock genes are deeply conserved in most animals, so that basically the same set of genes controls the biological clocks of both fruit flies and human beings. Some flies (and some humans) have gene variants that bring about problems like delayed-sleep-cycle sydrome, but essentially everyone can entrain their biological clock by controlling light exposure.

This study relies on finding associations in a large data set, which is not really a complete scientific study. It's at best a hint about where scientists should conduct future research.

If you're just looking at correlations, it can be easy to miss hidden variables, even when attempting to control for them with statistical methods.

Compare with a well-known Standord study where athletes were asked to maximize their sleep, and then their results compared to when they got the "normal" amount of sleep. They showed a notable improvement while maximizing sleep.

Ctrl-F sleep debt. Zero results found.

If you're reading an article on sleep studies and it doesn't mention sleep debt, it's not giving the whole picture. Look up William Dement for more info.

Now just for a bit of info so it may help others... for years I had the problem of going to bed around 10pm and then lying there awake for hours. Sometimes almost to 1am. Classic insomnia, until I read a book on sleep by William Dement, it all started to make a bit more sense - I was going to bed too early for my body and not accumulating enough sleep debt...

So the solution was easy! Stay up later. Instead, I started going to bed at around 11pm. I started falling asleep easier (within the recommend 20 minutes) and didn't have the issue of insomnia any longer. However this did lead onto another issue - headaches. After years of suffering from insomnia I had found the solution but then it lead to headaches. I chose headaches. But then I A/B tested some more. I now go to sleep between 12am and 12:30am. Headaches gone. Counter-intuitive, I completely agree. But headaches begone!

So IANAD (I am not a doctor), but if you're suffering from insomnia, try staying up an hour later each night to accumulate a bit of sleep debt. And if it's working but you're then getting headaches, try staying up another hour. If you do experiment with this, shoot me an email (see my profile). I would be interested to see if it works for more people or completely backfires.

(For the curious, I get out of bed at 5:05am every morning for work. So under 5 clean hours each night, no insomnia, no headaches)

Edit: I should have put more info on William Dement, otherwise people may think he's just another fly-by-night "expert" - Dr. William C. Dement, M.D., Ph.D., the world's leading authority on sleep, sleep disorders, and the dangers of sleep deprivation. He is the director and founder of the Stanford University Sleep Disorders Clinic and Research Center, the world's first sleep disorders center.

The evidence for medium- to long-term sleep debt is sketchy at best. Certainly in the short term (1-3 days) if you are deprived of sleep, or if you're chronically short on sleep, there's all sorts of cognitive and physiological effects.

But after over longer terms of a week or more, after returning to a normal sleep schedule, it's more complicated. Much of the 'overtired' feeling and cognitive effects come from being deprived of slow-wave sleep (SWS), which you get in the deepest phases of sleep. It's in this phase of sleep that motor skills are consolidated, and it seems to be the 'physically restorative' part of sleep. This is opposed to REM sleep, which you get in the lighter phases of sleep and is where you dream and where memories are consolidated. Unlike SWS, there are very few side effects to being deprived of REM sleep. In a typical eight-hour sleep there will be several cycles of sleep, totalling about four to five hours out of eight spent in SWS, and the remainder in REM and in transition between states.

As for sleep debt and why it doesn't really exist beyond the short term, it comes down to what sleep researchers call sleep architecture, or how the cycles and phases of sleep are arranged through a night's sleep. For example, there's typically a bias towards getting more SWS in the first half of the night, and more REM sleep in the second. Here's what a typical night's sleep looks like (Stages 3 and 4 are SWS sleep):

http://en.wikipedia.org/wiki/Sleep_architecture#mediaviewer/...

Your sleep architecture changes under sleep deprivation. If you are selectively deprived of SWS one night (e.g. by an evil sleep researcher waking you up any time you enter SWS), you will spend more of the next night in SWS to compensate. If your sleep is reduced gradually over time, your body will sacrifice REM sleep to maintain the same amount of SWS -- about four to five hours a night. As I said before, not getting much REM sleep has few side effects.

This is why you are able to sleep only five hours a night and still feel fine: your body simply adjusted to spend very little time in SWS. If I could guess, I'd say you probably have very few dreams anymore, maybe just one occasionally, shortly before waking up? I can't explain why this helped your insomnia or headaches, because I don't know much about how an insomniac differs from a typical person. But it's not to do with sleep debt.

Thanks, I've never heard of sleep architecture before.

> If I could guess, I'd say you probably have very few dreams anymore, maybe just one occasionally, shortly before waking up?

Wow, that is spot on. I've been doing under five hours of sleep for the past six months now, and I made an comment the other week to my wife that I no longer dream. Given what you said above, it agrees with what I'm experiencing.

Glad to help. I wouldn't worry about any of this, by the way. If you feel better on this schedule and don't notice any cognitive effects (e.g. forgetfulness of things that happened in the last two weeks or so), then do what works for you. There's some evidence that sleep restriction, which is the term in the literature for what you're doing (as opposed to sleep deprivation), can actually lengthen your lifespan. If you're a mouse, anyway.

But you're at about the limit: the number I recall is 5.5 hours of sleep being the minimum, but there's probably some individual variation there of +/- 0.5h or something.

> can actually lengthen your lifespan. If you're a mouse, anyway.

Interesting. But I would add that because I'm already winning since it's "time awake" vs "time alive". If sleeping 15 hours a day let me live 10 more years, what's the point if most of them aren't awake :)

I went into the opposite direction: my sleep schedule now wants to be 2am or later and yet I still have to be up by 7:30 to make it to work on time.

I will agree though that I have to be in a state where my body just can no longer stay awake before I fall asleep. I can't lay in bed. I can't read, I have to literally go until I can't any longer. I'm currently in a month or so of terrible sleep by it being broken up into 2 intervals where I wake up in the middle of the night and stay up for a few hours until my body wants to shut back down again.

Insomnia is an insufferable bitch for the most part. I will say YMMV on anything you change regarding sleep habits. I personally need to be in a massive amount of slept debt to properly fall asleep but it can easily backfire quite easily if I'm not careful.

for years I had the problem of going to bed around 10pm and then lying there awake for hours

Do you do any sports? Running or swimming for an hour (or cycling for two) works well for me.

Yeah, I'm actually very active. Gym, basketball, martial arts. Sorry to say that sport never made a difference with my sleep.

Edit: see above - I realised that sport actually kept me awake (tossing and turning, not falling asleep within 20 minutes).

I lift most nights but by the time I get home from work and to the gym it's like 7pm. Workout for 1-2 hours and it's nine. Trying to come down from that before midnight doesn't work. Then it's up at 6ish again.

I run, lift, and do heavy Colorado trails at high heartrate levels. I find exercise makes it generally more difficult to sleep. Has been a problem for years, only get real sleep on my rest days.

Thinking about this more, I'd agree with this too. That and mediation. Back in my insomnia years, I got so bored of lying there awake that I took up meditation. I found that when I meditated (sometimes up to an hour) I found that I needed even less sleep.

Given what we now know about chronic cardio and it's incredibly damaging effects on the body and the terrible consequences of losing sleep and the fact that it's been a problem for you for years you sure sound resigned to it all. I hope you don't suffer the typical consequences of such a dangerous lifestyle. Consider reading this: http://www.marksdailyapple.com/the-evidence-continues-to-mou...

Given what we now know about chronic cardio and it's incredibly damaging effects on the body

That looks like FUD from somebody who's living depends on blogging FUD. Of course, it's possible to train too hard, but this is very bad advice for the average (slightly overweight, not very active) person. If you worry about training too much, go talk to a sports physician and take a cardiac stress test. Or just run so slowly that you can breathe through your nose only.

Nope, science. FUD is pretty much what you replied with! :)

I only have this issue when I run at night. It seems like intense cardio in the morning is a better idea with regards to lessening sleep disruption.

Actually the correct answer to "how many hours should I sleep?" is: it depends.

I spend several hours a week breaking down my body by lifting extremely heavy weights at the gym each week. I don't feel good with 7 hours of sleep. My body needs to repair itself.

It's definitely not a fixed rule. I slept 7 hours last night and I feel miserable today, dull and tired. If I get 8-10 hours, I feel great.

Yeah, same here. I sleep as much as 10 hours a day -- basically until I wake up naturally without the alarm clock.

> "And stay off electronic devices a couple of hours before going to bed."

For many of us this will be the hardest part (and also a large source of sleep problems).

You might want to try f.lux. Since the problem with electronic devices seems to be blue light, changing the hue of the screen to a more reddish tone seems to prevent the serotonin production inhibition associated with blue light.

I love f.lux. I don't know if it has actually helped me fall asleep faster, but I find myself getting a lot less eye strain when working at night. I just wish I could find a similar app that actually works well for android. Any suggestions out there?

Twilight is pretty good

Personally I use Lux on Android.

Oh noes, I get horribly tired from this instantly... as in "I just want to finish some..zzzZZZ".

Or redshift, for Linux.

Though I rarely get it, I definitely feel my best after 12-13 hours of sleep. I've never understood how the world seems fine with just 7 or 8.

"I definitely feel my best"

A careful read of the article indicates its from the perspective of maximization of lifespan and maximization of short term productivity. Why must they both be the same or have anything to do with each other, beyond numerological coincidence?

You're talking about a completely different metric, which is quality of life.

From personal experience in .mil my "combat effectiveness" for uncle sam probably was maximized by only being able to sleep for about three hours per night. I would not wish that hell on anyone.

There should be more to life than merely making someone else richer at the fastest rate you're capable of, or being the last guy in your cohort to die, while suffering in agony.

If I sleep over 6-7 hours I find it incredibly difficult to get to sleep the following night. The problem for me is I am perfectly happy sleeping 12 hours :) If I actually obey my alarm and get up after 6 hours of sleep that seems perfect to get me through the day (without caffeine) and fall asleep quite quickly the next night.

Same there. If I sleep as much as I want (8-9 hours), my day tend to be 26+ hours. So I'd go to bed later and later. 7/17 formula works fine for me. I feel dizzy with 6 hours of sleep only though.

That's exactly my problem. A few years ago I tried to follow that pattern. I got as much sleep as I liked (8-9 hours usually) and went to bed when I was tired. It just got later and later until I went to bed just before sunrise and woke up just after sunset. Missing sunlight was actually quite horrible so I ended the experiment after that!

I don't have any sources but for a lot of people this seems to decrease with age. I'm 28 and I can still sleep for 10-12 hours if I don't have any reason to get up, which is rare. However, I don't think my dad can actually sleep more than 8 hours if he wanted to.

I was under the impression that 7.5 hours was optimal because it falls within the recommended 7-9 hours and occurs at the end of a sleep cycle, which should help you feel more refreshed and alert upon waking.

Just keep in mind that nothing is exact. That "1.5 hours" is approximate, and will vary between people, and will probably vary from night to night depending on all sorts of things you'd never think of, and maybe between the start and end of the night. Plus I'm pretty sure switching from "awake" to "asleep" isn't instantaneous, so you have to count that time as well.

Yup, sleep cycles are 1.5 hours each and most humans need 5 of them. As long as you don't break out of a sleep cycle before the 1.5 hours is completed you tend to feel pretty awake when you do wake up, even if it's only been 3 hours.

So the "health" section of the WSJ needed to come up with a story about sleep, and found that many things correlate with the number 7.

The stone age-like study mentioned at the end, for example, simply found that their participants slept longer when they had no access to electricity: "subjective assessments of health and functioning did not reveal any relevant changes across the study." So why 7.2 hours? Sunset at 22:00, sunrise (or excessively loud birds!) at 5:30...

Even the title seems wrong. Sleep cycles take about 90 minutes each, so if I plan to wake up after a certain amount of time, I pick a multiple of 90 minutes, i.e. neither 7 nor 8 hours.

Sleep cycles don't all take exactly 90 minutes. The first one takes about 90 minutes, and each subsequent sleep cycle decreases in duration throughout the night. The last sleep cycle before you wake up will take significantly less than 90 minutes.

^ this; I find waking up after 7.5 hours (ish) to be easier than at 8 hours (ish). Half an hour makes quite some difference.

So, the article starts, and ends, with recommending 7-9 hours of sleep. Everything in between mostly supports those two values.

What's the real answer, proposed by reality and this article? Find out for yourself what your sleep duration should be.

Seems to me that the real purpose of this article was to remind folks that 5 hours is generally not going to be enough sleep, and 10+ hours might be a sign something's wrong.

To add to anecdotal evidence: What's worked for me is having a set wake-up time every single day of the week, and going to bed when I'm tired. Turns out I naturally want right around 8 hours of sleep, give or take 30 minutes on a day-to-day basis.

but how do we know much of that "naturally" is actually from decades of sleeping ~8 hours of day

I find research that starts with the assumption that humans require identical amounts of anything to be absurd. People are metabolically different from each other - the optimal average has no bearing on what I should do, it only indicates the course that is most likely to be correct, ignoring all specific information about myself.

I have a lot of information about myself that differentiates me from the aggregate (and so should most people), so this recommendation is more dangerous than it is useful.

I wonder at which point in time did we stop going to sleep when we were tired and just started subscribing to some random number like 8 hours of sleep per day.

Humans are so stupid.

The Industrial Revolution, probably. You can't simply "go to sleep when you're tired" when you have to allocate x hours to labor per day - everything you do is synchronized to either education hours or work hours for most of your life. So 8 hours of sleep with 8 hours of work and 8 hours of leisure per day.

I'm seeing lots of researches being cited here, but, were those people healthier because they got less than 8 hours of sleep, or was there some other factor causing them to get / need less sleep which also helped their health?

7hrs is completely consistent w/ my current, quite sustainable, sleep pattern.

I sleep 8.5-9 hours a night. I feel like shit if I get less than 8. I think it largely depends on the person

How about... 3?

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