## Only 5-6.5 hours of sleep is ideal?

I knew that this amount of sleep (or less) seemed to work for some people. However the general view was that most people needed 7-8 hours of quality sleep for good health. This follow up study in women seems to refute this. The researchers followed over 400 women over 14 years with minimal loss to follow up and discovered the optimal amount of sleep associated with reduced mortality was significantly less (at least for women in southern California).

EDIT: It should be understood that this is only one study and for various reasons, should not be considered the last word.

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 Admin That's not the first time I read about research linking amount of sleep with mortality. However, I have never seen statement "all other things being equal" when results are described. This makes me always wonder - what if those sleeping longer are those that don't have to wake up early, because they are already retired, or don't work because of some disabilities? In other words - what if amount of sleep is just a proxy for something else, something that is more important?
 unless we see the details , its hard to comment on the study we do not know - what was the cause of mortality in all the cases, it could be anything from car accidents to diseases

## Only 5-6.5 hours of sleep is ideal?

 Quote by Borek However, I have never seen statement "all other things being equal" when results are described. This makes me always wonder - what if those sleeping longer are those that don't have to wake up early, because they are already retired, or don't work because of some disabilities? In other words - what if amount of sleep is just a proxy for something else, something that is more important?
Apparently the lead author Kripke has published a lot of studies on sleep. I was looking for this particular paper online but only found the text of the announcement that I linked. I haven't had chance to look at some of the other publications, but this finding was apparently a surprise.

Studies that use large organized observational research project populations, like this study or Framingham, rely on internal controls and use multivariate analysis to control for potential confounding factors. The one you mention is one that probably can be controlled by stratifying on age which is always done in epidemiological studies. Beyond that you would want to control for factors like work status, co-morbidity, etc. Not having seen the paper, I don't know what factors were actually used in adjusting risk ratios other than age.

 Quote by cosmos 2.0 unless we see the details , its hard to comment on the study we do not know - what was the cause of mortality in all the cases, it could be anything from car accidents to diseases
You're correct. However, to confound an outcome measure, there needs to be an association between the potential confounding factor and both the putative risk or benefit factor and the outcome which could produce the same result . So you would need to show that having an illness or more car crashes is associated with both less sleep and reduced mortality.

 Quote by SW VandeCarr You're correct. However, to confound an outcome measure, there needs to be an association between the potential confounding factor and both the putative risk or benefit factor and the outcome which could produce the same result . So you would need to show that having an illness or more car crashes is associated with both less sleep and reduced mortality.
medical trials require a large sample size to overcome confounding factors.
besides in this study some things are not well understood -since we do not have the details

In real sense -how can a extra hour of sleep have increased risk of mortality i.e. if a person sleeps 7.5 hrs instead of recommended 6.5 hrs

It would seem a extra hour of sleep is always good especially for age group mentioned in the study

 Recognitions: Gold Member Science Advisor I think "required" amount of sleep is one of those things that will turn out to be far to individualized for following a "general rule"-Much as how "nutritional guidelines" have been adjusted, adjusted again and re-adjusted over the years. At the 'group level' figuring out things like amount of sleep needed probably isn't a very feasible investigation. It also depends on what the individual wishes to maximize. For instance, your memory prowess has been consistently linked to a good nights rest. I find for myself that I can function fine on 4-5 hours of sleep, but when I'm trying to learn I need more--Least I want to retain any information. Similarly, I've seen people in very stressful job situations who find a long nights sleep be most comforting--And anything which successfully lowers the cortisol levels ain't a bad thing.

 Quote by bobze I think "required" amount of sleep is one of those things that will turn out to be far to individualized for following a "general rule"-Much as how "nutritional guidelines" have been adjusted, adjusted again and re-adjusted over the years. At the 'group level' figuring out things like amount of sleep needed probably isn't a very feasible investigation. It also depends on what the individual wishes to maximize. For instance, your memory prowess has been consistently linked to a good nights rest. I find for myself that I can function fine on 4-5 hours of sleep, but when I'm trying to learn I need more--Least I want to retain any information. Similarly, I've seen people in very stressful job situations who find a long nights sleep be most comforting--And anything which successfully lowers the cortisol levels ain't a bad thing.
I'm not cutting back on my 10 hrs sleep daily just because of this study (slight exaggeration, but I'm not changing my sleeping habits). The issue is if we accept the stated results, how do we explain why women who claimed to sleep fewer hours appear to be living longer? Maybe women who lie about the amount of hours they sleep in the direction of fewer hours just tend to be longer lived. Then you have to explain why women who lie seem to live longer. A sample of over 400 women has a fair amount of statistical power.

In fact, I understand the sleep data were collected in the 1990s and some kind of monitoring device was used to detect sleep patterns. This group has a lot of publications on the internet and have a good reputation as investigators in sleep research. I just want to read the paper when it comes out. So far, I've just seen announcements. I personally don't like these kind of pre-publication announcements. I want to see some details and p values.

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 Quote by SW VandeCarr I'm not cutting back on my 10 hrs sleep daily just because of this study (slight exaggeration, but I'm not changing my sleeping habits). The issue is if we accept the stated results, how do we explain why women who claimed to sleep fewer hours appear to be living longer? Maybe women who lie about the amount of hours they sleep in the direction of fewer hours just tend to be longer lived. Then you have to explain why women who lie seem to live longer. A sample of over 400 women has a fair amount of statistical power. In fact, I understand the sleep data were collected in the 1990s and some kind of monitoring device was used to detect sleep patterns. This group has a lot of publications on the internet and have a good reputation as investigators in sleep research. I just want to read the paper when it comes out. So far, I've just seen announcements. I personally don't like these kind of pre-publication announcements. I want to see some details and p values.
Did they monitor the women during the day for naps?

I need 10 hours a day to function properly, and I'm not getting it and everyone can tell that my memory, reflexes, stamina, and overall ability to understand verbal and written information are close to nill. It has also negatively affected my ability to cope with pain and heal.

 Quote by Evo Did they monitor the women during the day for naps?
I don't know. This group is devoted to sleep research so it seems they would have considered naps. However I'm not sure they collected the original data. Again, I'm waiting for the paper.

 I need 10 hours a day to function properly, and I'm not getting it and everyone can tell that my memory, reflexes, stamina, and overall ability to understand verbal and written information are close to nill. It has also negatively affected my ability to cope with pain and heal.
Like Bobze says, individual needs vary. Assuming the finding holds up, it may not be a cause-effect relation. I would not recommend anyone change their sleep habits if they feel they are getting the amount of sleep they feel they need. Remember, the quality of sleep is important too. If you feel tired during the day and are able to take a few short naps, they can be very beneficial.

 i truly believe that sleep time totally depends on the individual. some people can function perfectly at 4 hours of sleep (my sister), yet others such as myself need 8. i cannot function at all when i sleep for only 6 hours. i feel fatigued the whole day and i feel like my eyes are going to pop out. so i really think it depends on the persons body type and other factors included.

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 Quote by Borek I have never seen statement "all other things being equal" when results are described.
I take it you don't read econ, then, where "certeris paribus" litters almost every page.

 natural sleep habits (a very interesting read, btw): http://www.historycooperative.org/jo.../ah000343.html

 Quote by CRGreathouse I take it you don't read econ, then, where "certeris paribus" litters almost every page.
I meant - I have never seen it when reading about amount of sleep vs mortality.

My own experience with controlling amount of sleep is that's just like trying to squeeze a balloon - when you embrace it and compress, bulges appear in random places. When I sleep short in the night, I am getting sleepy at random hours during a day. Mostly in the nap window around 3-4 p.m., but not only.

Interestingly, I am an owl, and my nap window is about two hours later than Marzena's (she is early bird type).

In case you wonder - no idea how the "nap window" is properly called in English, but it is thing known from the sleep research - there is a time during a day when it is much easier to fall asleep than at other hours, and it happens to be in an early afternoon. (See The Enchanted World of Sleep by Lavie Peretz).

 Quote by Maz88 i truly believe that sleep time totally depends on the individual. some people can function perfectly at 4 hours of sleep (my sister), yet others such as myself need 8. i cannot function at all when i sleep for only 6 hours. i feel fatigued the whole day and i feel like my eyes are going to pop out. so i really think it depends on the persons body type and other factors included.
I agree with you. But the point I'm trying to make is that this study raised a question. They're a reputable group that found an unexpected statistical association. I think this begs for an explanation. IMO here are some possibilities not any particular order:

. The association is indirect (non causal). Some factor or factors are common to women who require less sleep and women who live longer.

. The quality of sleep is more important than duration. Women who sleep less sleep better and this promotes longevity, other things being equal.

. The association is direct (causal). The ideal number of hours of sleep daily is one predictor for longevity and this ideal is less than we thought.

. The association is spurious. Even low p values do not rule out spurious associations.

. The original measurements of hours of sleep under-determined the true amount, possibly because it didn't include naps (courtesy of Evo).

 Quote by Evo Did they monitor the women during the day for naps? I need 10 hours a day to function properly, and I'm not getting it and everyone can tell that my memory, reflexes, stamina, and overall ability to understand verbal and written information are close to nill. It has also negatively affected my ability to cope with pain and heal.
Evo, honestly speaking, I haven't noticed the inabilities that you mention. Yet, I haven't been following everything you have posted to physicsforums. (I'm not a troll.lol!) I am concerned about your issues of pain and healing. Perhaps you've discussed this with your physician. I do hope you will feel better soon.

The American Academy of Sleep Medicine has a section strickly for women. Sleep & Women states the following: