Measuring sleep needs: Older people may need less than younger, study finds

A good night's sleep is important at any age. But what constitutes a good night's sleep for people older than 65?

Some researchers now say the answer may be surprisingly reassuring: Healthy older people may need less sleep than younger people to feel alert during the day.

The idea is not proven, and some experts are skeptical. But it would come as good news to a lot of people, since it's undisputed that older people typically sleep fewer hours, with more awakenings and fewer minutes of deep sleep. And, at a time when many older folks still hold jobs, do volunteer work, care for children and drive cars, it matters.

"The party line has long been that we do not think sleep needs change from the early 20s until death, though we do know that many older people get less sleep," says Lisa Shives, a physician who specializes in sleep medicine in Evanston, Ill.

Under that conventional view, "sleep ability" often decreases with age, but "sleep need" — the amount people need to feel and function well — does not, says Miroslaw Mackiewicz, who directs sleep research at the National Institute on Aging in Bethesda, Md.

A study published this month in the journal Sleep questions that view. For the study, British researchers brought 110 healthy adults into a sleep lab and observed a night of sleep. As expected, those ages 20 to 30 had the longest, deepest sleep, followed by those ages 40 to 55. Those ages 66 to 83 slept least, about 43 minutes less than young adults.

The next day, researchers gave the subjects a common test of sleepiness: They put them in a darkened room, asked them to nap and counted the minutes until they fell asleep. Result: Older people took longest to nod off. Then the researchers disrupted some of the subjects' sleep for two nights. When tested again, older people appeared no more sleep-deprived than the young ones — and possibly less.

Taken together, the findings suggest that healthy older people are less sleepy in the daytime than healthy young people, the authors write. Older folks may get less sleep because they need less, say the authors, led by Derk-Jan Dijk of the Surrey Sleep Research Centre in Guildford. They note that they did not test evening sleepiness.

Knowing briefer snoozes are normal could actually improve sleep quality for some folks who fruitlessly spend extra hours in bed, the authors say.