How many hours of sleep are best for you every night? Do you sleep the same amount every night?
On average, Americans sleep less during the week, 6-plus hours, and creep up above 7 hours on the weekend. In a recent study discussed in the Wall Street Journal here, some findings are familiar: skimping on sleep by as little as 20 minutes has cognitive effects.
(Another recent study suggested that going 24 hours without sleep evokes some symptoms of psychosis, or true insanity: doctors on call beware. Or rather: patients being treated by doctors on eternal call, beware!)
Back to the study at hand. Researchers found that the lowest rates of sickness and death (morbidity and mortality) were in the group sleeping 7 hours a night. Less sleep and more sleep showed worse health outcomes. The optimal range was actually 6.5 to 7.4 hours, so 7 hours give or take 30 minutes. In elderly (what do they mean by elderly?) women, 6.5 hours was the sweet spot in the study.
The article concedes that data on ill effects of excess sleep are problematic: perhaps the health problems came first and the sleep problems are a result of pre-existing health issues. Excess sleep (or inadequate sleep) can also be a sign of depression, which, unfairly, raises your risk for other health problems as well.
We have talked before about the clear detriments of inadequate sleep. Particularly for people in the process of recovering from or resolving their insomnia, it makes good medical, common, and individual sense to sleep extra hours. Extra time asleep won't completely repair the ill effects of sleep loss, but those extra z's can definitely help.
I would say that the bottom line is still individual, that more people have inadequate sleep (either because they are short-changing themselves or because they have some problem with insomnia) than excessive sleep, and that it's welcoming to see more research being done in the area of sleep.