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How much sleep does one need?

SAN DIEGO, CALIFORNIA. It is often assumed that insomnia and difficulties in sleeping are bad for your health. Researchers at the University of California now challenge this belief. Their study involved more than 1.1 million men and women between the ages of 30 and 102 years. The participants were asked about their sleeping habits and frequency of insomnia at the beginning of the study period. Six years later 9.4 per cent of the men and 5.1 per cent of the women had died. The most common causes of death were cardiovascular disease and stroke, which accounted for 43 per cent of all deaths among women and 49 per cent among men. Cancer accounted for 36 per cent of deaths among women and 29 per cent among men. The researchers found that people who slept an average of 7 hours every night had the best survival rate. People who slept more than 8.5 hours or less than 4 hours per night had a 15 per cent increase in overall mortality as compared to those who slept 7 hours every night. People who regularly slept 10 hours or more had a 30-40 per cent higher mortality than did 7-hour night people.

There was no excess mortality among people with insomnia, but those who regularly used sleeping pills had a 10-25 per cent higher mortality than non-users. The researchers offer no rational explanation for their findings, but conclude that people who sleep between 7 and 7.5 hours a night tend to live longer.
Kripke, Daniel F., et al. Mortality associated with sleep duration and insomnia. Archives of General Psychiatry, Vol. 59, February 2002, pp. 131-36 [48 references]
Buysse, Daniel J. Can sleep be bad for you? Can insomnia be good? Archives of General Psychiatry, Vol. 59, February 2002, pp. 137-38 (commentary)

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