Too much sleep
shortens your life
Researchers from the University of California at San Diego found in a study of adults aged 30 to 102 that people who slept eight hours a night were 12 per cent more likely to die within the study's six-year period compared to those sleeping seven hours. The increased risk rose to 15 per cent for participants reporting more than eight hours or less than 4 1/ 2.
"People who sleep five, six or seven hours have nothing to worry about. There is no evidence that people need eight hours of sleep ... The only basis for that is it's what grandma used to say," Dr. Daniel Kripke, a UCSD professor of psychiatry and the study's lead author, said in an interview.
He said the study shows that longer sleep is a risk factor for cancer as well as heart disease and stroke, but more research is needed to determine whether sleeping longer should be added to the growing list of one-time pleasures - like smoking and alcohol - now deemed hazardous to your health.
Other researchers also cautioned against strict interpretation of the findings. "Many studies show that if people don't get adequate sleep they are very sleepy during the day. Their ability to perform tasks is impaired, the risk of accident is higher and people are crabby," said James Walsh, a sleep scientist and president of the National Sleep Foundation. He also said the San Diego study was not a true random sampling of the population and more studies are needed.Kripke, an eight-hour-a-night sleeper, said the average American gets 6 1/2 hours of shut-eye, which is just fine. "Neither in terms of health or survival is there any evidence that eight hours of sleep is better than six or seven. Nor is there any evidence that longer sleepers are rich or have more fun," he added.
Walsh said the weight of evidence still suggests that the average adult needs 7 1/2 to 8 1/2 hours of sleep to be wide awake, energetic and alert during the day.
The study found little, if any, connection between death rates and insomnia, which it said patients commonly complain of even when their sleep duration is within normal ranges.
Kripke said people who take sleeping pills were shown to have a slightly higher death rate than others, but because the data was collected in the 1980s, the results are not necessarily reflective of newer types of sleeping pills.
The research, which addressed sleep issues as part of a broader cancer prevention study done with the American Cancer Society, is published in the Archives of General Psychiatry.
An accompanying commentary by Dr. Daniel Buysse and Dr. Mary Ganguli of Western Psychiatric Institute and Clinic in Pittsburgh also cautioned that sleep deprivation can raise accident rates.
The best survival rates were found for people who slumbered seven hours a night - about 32 per cent of women in the study and 34 per cent of the men fell into this category. People with as little as five hours of sleep lived longer than participants with eight hours or more per night. - Reuters