PEOPLE WHO sleep for more than eight hours a night do not live as long as those who sleep for six hours, according to the biggest study yet into sleep patterns and mortality.
Scientists have no explanation for the findings and do not know if they mean people who like a lie-in can extend their lives by sleeping less.
Although it is a common belief that sleeping for at least eight hours a night is vital for health and well-being, the six-year study involving more than 1.1 million Americans older than 30 found that those who slept for less than eight hours were far from doing themselves any long-term harm.
"Individuals who now average 6.5 hours of sleep a night can be reassured that this is a safe amount of sleep. From a health standpoint, there is no reason to sleep longer," said Daniel Kripke, a professor of psychiatry at the University of California, San Diego, who led the study published in the Archives of General Psychiatry and discussed at the meeting of the American Association for the Advancement of Science in Boston.
Dr Kripke said: "We don't know if long sleep periods lead to death. Additional studies are needed to determine if setting your alarm clock earlier will actually improve your health."
The scientists, who were funded by the American Cancer Society, found that the best survival rates were among the men and women who slept for seven hours a night. …