Do bedtime times really matter?

September 10, 2009 2:44 PM

"An hour of sleep before midnight is worth two hours after". Is there any science to back this up, or is it just an old wives' tale?

My sister believes that "an hour of sleep before midnight is worth two hours after", having read it in a book by a religious writer she follows. I think it's an old wives' tale that goes back a long, long time, before people had much knowlege of REM cycles, circadian rhythms, etc, in the same vein as "early to bed, early to rise, makes a man healthy, wealthy, and wise". She's naturally an early bird, I'm more of a night owl. We're not talking completely opposite sleep times here - more like the difference between a 9 pm bedtime, or staying up until midnight. Anyone have some actual science to add to the discussion?

posted by dorey_oh to health & fitness (18 comments total)

Night shift work causes cancer and people with delayed sleep phase are more likely to be depressed, so it seems that being awake at night isn't very good for you long term (thought, obviously, we have to be careful about drawing such inferences, not in the least because of the ease with which we confuse cause and effect).
posted by phrontist at 2:50 PM on September 10 [1 favorite]

Night shift work causes cancer and people with delayed sleep phase are more likely to be depressed, so it seems that being awake at night isn't very good for you long term (thought, obviously, we have to be careful about drawing such inferences, not in the least because of the ease with which we confuse cause and effect).

I'd suspect that in both cases these results are from forcing people/oneself to live in a schedule so far off what comes naturally to them.

Anyway, certainly not in my case. Sleep before about 3 or 5 am isn't real sleep for me and I can only doing it by running myself into the ground on 5 or so hours a night during the week. Real sleep - sleep that actually seems to leave me rested - comes to me after 5 or 6 am. (I know day people who have worked nights who say the same about sleeping in the day that I say about sleeping at night). Personal experience probably does not equal "actual science", though.
posted by dilettante at 2:58 PM on September 10 [1 favorite]

This implies that sleeping for four hours from 8:00 PM to 12:00 AM is equivalent in “worth” to sleeping for eight hours from 12:00 AM to 8:00 AM, which is quite a stretch.

Then again, it is just a folk saying. A stitch in time might not save precisely nine, either.
posted by letourneau at 3:16 PM on September 10 [3 favorites]

I heard a scientist or doctor on the radio some years ago who said something which kind of maps to that idea, although it's not the same exactly -- essentially it was "if you're short of sleep, you can't make up the deficit by sleeping late, only by sleeping early".

So in other words, say you normally sleep from midnight till 8 AM. You would be better off, according to this theory, going to bed two hours early and sleeping 10 PM - 8 AM than you would if you went to bed at the normal time and lay in till 10 AM.
posted by AmbroseChapel at 4:05 PM on September 10 [2 favorites]

I don't go to sleep until 4am every night, and I am perfectly happy and wouldn't change a thing about my life.
posted by VC Drake at 4:06 PM on September 10

If that's the case, I'm either screwed or very well-off, depending on which side of midnight you consider my sleep to be falling. I've worked nights for the past five years and, with limited exceptions these days, I sleep better during the day than at night. For example, I'm off this week to change my schedule back to "days" in preparation for a vacation trip next week. These past two nights when I've slept, I wake up groggy and have been sleepy most of the day. This seems like an "old wives tale" to me, intended to be cautionary against spending 24+ hours awake or staying up all night being "disreputable."

Oh, and on the "night shift causes cancer," I wonder if it's more of a problem for people who wake up after dark and go to sleep when the sun is at a full burn or for everybody who is awake all night?

I ♥ anecdotal evidence...
posted by fireoyster at 4:13 PM on September 10

She's naturally an early bird, I'm more of a night owl.

This may be genetic (note: this study was in mice, I can't find if it's been replicated in humans yet). Quite a lot of research has been done in clock genes and circadian rhythms, here's a review, there are likely others.

This only answers part of your question because it doesn't take into account things like REM and other types of sleep. I always heard that the deeper sleep happens at the end of your sleep time rather than the start so getting long enough chunks of sleep is important, which doesn't necessarily agree with what your sister is saying (i.e. actually the later sleep is more important than the early stuff, or maybe getting enough sleep all at once is more important than when you start). But I don't have any citations to back this up right now (and of course I could be mis-remembering), sorry!

It's a complex topic, quite widely researched, not always well understood, and hopefully others give you more science to look at. Certainly different people have different sleep needs and different circadian rhythms. I'd be very surprised if there was one way of sleeping optimal for everyone.
posted by shelleycat at 4:29 PM on September 10

Not totally on topic, but I recently bought sort of cheap blackout curtains from Target and they've helped me learn to sleep in and sleep soundly. I think some people are more light sensitive than others, I am, particularly. Now I can sleep more soundly than I ever have, whenever I need to. I'm guessing that affects a lot of the studies. My room is pretty dark, even when it's pretty light out.
posted by sully75 at 5:12 PM on September 10

This is just anectdotal but on the strength of that saying, I have actually tried it-and I do feel better and more rested the next day. Maybe it has to do with cumulative hours awake BEFORE bedtime?
posted by St. Alia of the Bunnies at 5:30 PM on September 10

I recently changed my sleeping schedule to match my partners (early to bed, early to rise). As someone who normally goes to sleep at 2-3am and gets up at 10-11am (love the academic life by the by) it's been murder. Despite sleeping same number of hours, I felt groggy, I took naps (wtf? I never take naps) and was very unproductive. She took a trip recently and I went back to my late sleep/late wake habits and felt great! So there you have it, very anecdotal evidence telling you to not sweat the small stuff.


OR you can see what SCIENCE has to say about it (quick summery, early risers sucks, night owls win!)

Here comes the science (your question is damn timely as I just saw this article this very morning and sent it to my partner as proof that my sleeping schedule is a finely honed one).
posted by Smegoid at 5:53 PM on September 10

"night shift causes cancer,"

Maybe from irregular sleep patterns (ie switching sleep schedules on the weekend to hang out with dayshifters) coupled with too much caffeine and vending machine food?
posted by ian1977 at 5:57 PM on September 10

The 'night work causes cancer' article doesn't go into details about the study, but I would imagine that people who work the night-shift tend to be poorer and work in more hazardous environments (with more polution, etc) than those who work in the day shift, are less likely to get good nutrition (due to the logistics of eating at night), etc and so, it may not be the offset sleep that actually causes cancer.
posted by bsdfish at 6:26 PM on September 10

It's worth pointing out that science doesn't have many good answers about sleep; it's still a mystery, for the most part. Even the basic question of why we sleep doesn't have a settled answer yet. Given our ignorance, a definitive answer to this question seems premature.
posted by smorange at 7:02 PM on September 10

For me, more than anything, how well-rested or coherent I am when I wake up depends mostly on the duration of sleep. Waking up after a multiple of 1.5 hours seems to leave me at the end of a sleep cycle and i'm ready to hit the day without any caffeine. If I wake up at some other time.. I may need a few cups of coffee to shake off the grogginess. Typically sleeping from 2-8am will render me more awake than sleeping 1am-8am or midnight-8am.

Of course, if you haven't had much sleep lately, you will tire out quickly through the day. This has more to do with the number of hours slept than the effects of sleep cycles.
posted by mezamashii at 7:08 PM on September 10

If not sleeping through those hours causes cancer I'm going to die any minute now.

I'm a night bird. Always have been. Nocturnal. Over the years I've tried and tried again to reset my clock, get on a 'normal' pattern -- nunh-uh. Not gonna happen. I tried to do so because of reading people saying that I'd get better sleep or what-have-you, or trying to 'be normal'. So maybe I'd be able to do it for a few days or weeks and then slide, fast, into my normal pattern.

Which is not to say that I have not had jobs starting at six or seven or eight in the morning and made it there -- I have. But so much of the time I could not get to sleep until after midnight, sometimes way after midnight, and suffered accordingly through the work days/daze.

I do not have any idea how I did what I did as a young man, all the drinking and drugging until who knows what time and then working eight to ten hours of construction work. Even showing up was heroic. I did it for years. If I tried it today I expect I'd die in a week, and hope so.

It just feels different in the early morning hours. It's when I love to write, it's when I love to paint, it's when I love to go out, it's when I love, period; it's the time of day I love the most. It sounds so different, just is so different. I love to bop around Austin in the early morning hours, on my bike or in my pickup or walking, sometimes, through some of the neighborhoods that I like so much. I've got some fave all-night diners, sleaze-bag dumps, great fun to write there and eat greazy garbage and people watch. I love to drive all night, kick back and ease on through, sleaze on through, it's the most fun, unless it's country that I don't know and want to see as I wander through it.

Maybe this is how early risers feel through the day, probably it is. But I don't.

Glad to see that there are so many other night birds here on MetaFilter. Cool.
posted by dancestoblue at 12:06 AM on September 11 [1 favorite]

I think it comes from the concept of women getting their beauty sleep which was any sleep they got before midnight. Women, esp before the turn of the last century, worked long hours and usually didn't finish up much before midnight.
posted by x46 at 7:58 AM on September 11

I think they've done this study with nurses working days and nights shifts. The night shift nurses make more money, so there goes the poverty argument. I'm assuming that they are studying nurses working in the same hospital under similar conditions.
posted by sully75 at 2:40 PM on September 11

William Dement is one of the most highly regarded sleep researchers. A Google Books search of his The Promise of Sleep for the word "midnight" doesn't turn up anything about sleep before midnight being better.

In the book, he discusses research showing that sleep needs and cycles vary with age, and - if I recall correctly - even with gender.

I can't link to a direct cite, but several reviews of The Promise of Sleep mention its findings that teenagers experience a sleep cycle shift that makes it very difficult for them to fall asleep before 11 pm or midnight, whether they want to or not.

While I was looking for cites, I came across a fascinating article, Sleep We Have Lost: Pre-industrial Slumber in the British Isles, which presents extensive evidence that "Until the close of the early modern era, Western Europeans on most evenings experienced two major intervals of sleep bridged by up to an hour or more of quiet wakefulness."
posted by kristi at 12:13 PM on September 12 [2 favorites]