Women's study finds longevity means getting just enough sleep

September 30, 2010

A new study, derived from novel sleep research conducted by University of California, San Diego researchers 14 years earlier, suggests that the secret to a long life may come with just enough sleep. Less than five hours a night is probably not enough; eight hours is probably too much.

A team of scientists, headed by Daniel F. Kripke, MD, professor emeritus of psychiatry at UC San Diego School of Medicine, revisited original research conducted between 1995 and 1999. In that earlier study, part of the Women's Health Initiative, Kripke and colleagues had monitored 459 living in San Diego (ranging in age from 50 to 81) to determine if duration could be associated with mortality.

Fourteen years later, they returned to see who was still alive and well.

Of the original participants, 444 were located and evaluated. Eighty-six women had died. Previous studies, based upon questionnaires of people's sleep habits, had posited that sleeping 6.5 to 7.5 hours per night was associated with best survival. Kripke and colleagues, whose 1990s research had used wrist activity monitors to record sleep durations, essentially confirmed those findings, but with a twist.

"The surprise was that when sleep was measured objectively, the best survival was observed among women who slept 5 to 6.5 hours," Kripke said. "Women who slept less than five hours a night or more than 6.5 hours were less likely to be alive at the 14-year follow-up."

The findings are published online in the journal .

Kripke said the study should allay some people's fears that they're not getting enough sleep. "This means that women who sleep as little as five to six-and-a-half hours have nothing to worry about since that amount of sleep is evidently consistent with excellent survival. That is actually about the average measured sleep duration for San Diego women."

Researchers uncovered other interesting findings as well. For example, among older women, obstructive sleep apnea (pauses in breathing during sleep) did not predict increased mortality risk. "Although apneas may be associated with increased mortality risk among those under 60, it does not seem to carry a risk in the older age group, particularly for women," Kripke said.

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2 / 5 (4) Sep 30, 2010
Waste more of your life sleeping to live longer?
5 / 5 (3) Sep 30, 2010
Did you read the article? I mean really, it wasn't that long of an article.

"the best survival was observed among women who slept 5 to 6.5 hours"
5 / 5 (2) Sep 30, 2010
Hahaha, my bad :)
1 / 5 (1) Oct 01, 2010
This data (as given) is far from conclusive. For instance, is it the case that older women sleep longer and younger women of working age sleep less? If so, the study has only sorted the females by age with the older women being more likely to survive for a shorter period eg what difference would it make to the 81 years old in the study whether she slept for 6 or 12 hours ???
not rated yet Oct 01, 2010
The headline reads "Women's study finds longevity means getting just enough sleep"

That's not actually true. The studies show correlation but not necessarily causation or any functional mechanism by which excess sleep would increase risk of death.

I believe excess mortality associated with oversleeping has more to do with the fact that disorders and illnesses increase the need for sleep.

I sometimes sleep in excess of 10 hours and am still sleepy. I went to a sleep clinic and discovered I am actually only sleeping 40% of the time and only 2% of my time asleep is REM sleep. So I (or you) may be in bed for 10 hours but only 4 of that is spent sleeping and only about 10 minutes is REM, as opposed to 45 - 60 a person would normally get. I have trouble with both sleep onset and maintenance and it is not responsive to medication.
not rated yet Oct 01, 2010
My point is that intentional sleep abstention, waking up early even if you still feel like you need more sleep, is probably not going to help you live any longer. It will just ensure you live sleepier (and probably grumpier).
not rated yet Oct 01, 2010
I agree with you on all your points. I was going to write something along the same lines but then I read your comments!
[It is a bit worrying that even research studies (at least in the way they are reported, unfortunately I have no access to the original paper) seem so "thin on the ground" in terms of context and conclusions at times.]
5 / 5 (1) Oct 01, 2010
As usual, poor science and assumptions rather than conclusions. It implies a certain amount of sleep will make you live longer but maybe both are the result of some other factor, eg, a healthy active life, or, a relaxed atttitude to life etc. makes you inclined to live longer *and* sleep a certain length of time.
not rated yet Oct 01, 2010
Funny I thought just being awake would seriously increase risks of getting into harms way.
not rated yet Oct 01, 2010
I agree that this article at least represents poor science (unless the original study went well beyond what is stated). Disease and chronic conditions are probably causally related to either too much or too little sleep. A very weak heart will leave you tired and sleeping all the time. Psychosis or manic episodes will mean very little sleep. Both end badly and relatively soon.

My personal (tm) suggestion: don't use alarm clocks and sleep ... until you wake up. Whatever your particular body needs.

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