Oct. 1, 2010 —

Science Daily/University of California -- San Diego

A new study, derived from novel sleep research conducted by University of California, San Diego researchers 14 years earlier, suggests that the secret to a long life may come with just enough sleep. Less than five hours a night is probably not enough; eight hours is probably too much.

A team of scientists, headed by Daniel F. Kripke, MD, professor emeritus of psychiatry at UC San Diego School of Medicine, revisited original research conducted between 1995 and 1999. In that earlier study, part of the Women's Health Initiative, Kripke and colleagues had monitored 459 women living in San Diego (ranging in age from 50 to 81) to determine if sleep duration could be associated with mortality.

Kripke said the study should allay some people's fears that they're not getting enough sleep. "This means that women who sleep as little as five to six-and-a-half hours have nothing to worry about since that amount of sleep is evidently consistent with excellent survival. That is actually about the average measured sleep duration for San Diego women."

Researchers uncovered other interesting findings as well. For example, among older women, obstructive sleep apnea (pauses in breathing during sleep) did not predict increased mortality risk. "Although apneas 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 for women," Kripke said.

http://www.sciencedaily.com/releases/2010/09/100930161837.htm