How Much Sleep Do You Really Need?








By LAURA BLUETue Jun 10, 4:00 PM ET




Sleep is one of the richest topics in science today: why we need it,
why it can be hard to get, and how that affects everything from our
athletic performance to our income. Daniel Kripke, co-director of
research at the Scripps Clinic Sleep Center in La Jolla, Calif., has
looked at the most important question of all. In 2002, he compared
death rates among more than 1 million American adults who, as part of a
study on cancer prevention, reported their average nightly amount of
sleep. To many his results were surprising, but they've since been
corroborated by similar studies in Europe and East Asia. Kripke
explains.
Q: How much sleep is ideal?
A: Studies show that people who sleep between 6.5 hours and 7.5
hours a night, as they report, live the longest. And people who sleep 8
hours or more, or less than 6.5 hours, they don't live quite as long.
There is just as much risk associated with sleeping too long as with
sleeping too short. The big surprise is that long sleep seems to start
at 8 hours. Sleeping 8.5 hours might really be a little worse than
sleeping five.
Morbidity, [or sickness,] is also "U-shaped," in the sense that both
very short sleep and very long sleep are associated with many illnesses
- with depression, with obesity, and therefore with heart disease and
so forth. But the [ideal amount of sleep] for different health measures
isn't all in the same place. Most of the "low points" are at seven or
eight hours, but there are some at six and some even at nine. I think
diabetes is lowest in seven-hour sleepers, [for example]. But these
measures aren't as clear as the mortality data.
I think we can speculate [about why people who sleep 6.5 to 7.5
hours live longer], but we have to admit that we don't really
understand the reasons. We don't really know yet what is cause and what
is effect. So we don't know if a short sleeper can live longer by
extending their sleep, and we don't know if a long sleeper can live
longer by setting the alarm clock a bit earlier. We're hoping to
organize tests of those questions.
One of the reasons I like to publicize these facts is that I think
we can prevent a lot of insomnia and distress just by telling people
that short sleep is OK. We've all been told you ought to sleep eight
hours, but there was never any evidence. A very common problem we see
at sleep clinics is people who spend too long in bed. They think they
should sleep eight hours or nine hours, so they spend eight or nine
hours in bed, with the result that they have trouble falling asleep and
they wake up a lot during the night. Oddly enough, a lot of the problem
[of insomnia] is lying in bed awake worrying about it. There have been
many controlled studies in the United States, Great Britain and other
parts of Europe that show that an insomnia treatment that involves
getting out of bed when you're not sleepy, and restricting your time in
bed, actually helps people to sleep more. They get over their fear of
the bed. They get over the worry, and they become confident that when
they go to bed they will sleep. So spending less time in bed actually
makes sleep better. It is in fact a more powerful and effective
long-term treatment for insomnia than sleeping pills. View this article
on Time.com
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