6 or 7 Hours of Sleep Is Better, Study Says

Don’t fret if you don’t get eight hours of sleep a night: New research suggests adults live longer if they get six or seven.

Still, even the study’s authors say it is not time to reset the alarm clock.

The research is based on a nationwide survey of 1.1 million adults. It found that those who slept eight hours a night were 12% more likely to die within six years than those who got 6 1/2 to 7 1/2 hours of sleep. The increased risk was more than 15% for those who reported getting more than 8 1/2 hours or fewer than about four hours nightly.

The participants were ages 30 to 102. Few reported frequent insomnia.

The study was published in February’s Archives of General Psychiatry.

Sleep experts said the research has several flaws. It was not designed to look at sleep’s effect on longevity but relied on patients’ recollections of their sleep habits and did not ask if they took naps.

Dr. Phyllis Zee, director of Northwestern Memorial Hospital’s sleep disorders center, said the results probably do not reflect the general population because participants were not randomly selected but were mainly friends and relatives of volunteers for the American Cancer Society, which collected the data as part of a 1982 survey on cancer risks.

Zee said it is possible that participants who got little sleep or slept eight hours or more had medical problems that would explain their increased death rate.

The research neglects strong evidence that there are natural sleep variations, said psychologist Rosalind Cartwright of the sleep disorders center at Rush-Presbyterian-St. Luke’s Medical Center in Chicago.

“There are natural-born short sleepers who are perfectly healthy with fewer than six or fewer hours,” Cartwright said.