Secret to long life: Just enough sleep

By Elizabeth Mwai

The secret to long life may come with just enough sleep. A new study has found that less than five hours a night is probably not enough and eight hours is probably too much.

In a 14-year study by University of California, San Diego, the investigators found that women who slept between five to six and a half hours survived longest.

"The surprise was that when sleep was measured objectively, the best survival was observed among women who slept five to 6.5 hours," team leader Prof Daniel Kripke, says.

"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."

Best survival

In an earlier study, part of the Women’s Health Initiative, the researchers had monitored 459 women living in San Diego aged between 50 to 81 years to establish if sleep duration could be associated with mortality. Fourteen years later, the researchers returned to see who was still alive. They located and evaluated 444 of the original participants. Eighty-six women were reported to have died.

Previous studies, examining people’s sleep habits, had posited that sleeping 6.5 to 7.5 hours per night was associated with best survival.

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The study headed by Kripke whose 1990s research had used wrist activity monitors to record sleep durations, essentially confirmed those findings.

Kripke said the findings of the research should therefore serve to allay people’s fears that they’re not getting adequate amounts of sleep.

Consequently it implies that women who sleep as little as five to six-and-a-half hours have nothing to worry about.

During the study, the researchers also uncovered other interesting findings amongst older women. Obstructive sleep apnea — pauses in breathing during sleep — did not predict increased mortality risk.

"Although apnea 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 women," Kripke says.