POSTED IN THE TORONTO STAR, FEBRUARY 15, 2002.
Oversleeping can do harm
Study suggests too many Zs are as bad as too few
Prithi Yelaja
Medical Reporter
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It turns out that the Corsican conqueror Napoleon — who advocated six hours of sleep for a man, seven for a woman and eight for a fool — may have been right after all.
New U.S. research suggests that people who sleep five to seven hours live longer than those who sleep eight hours or more a night.
The average North American gets 6.5 hours of shut-eye a night, which is just fine, says the study's lead author, Dr. Daniel Kripke, a professor of psychiatry at the University of California at San Diego.
"People who sleep five, six or seven hours have nothing to worry about. There is no evidence that people need eight hours of sleep. That's just what Grandma used to teach, without any scientific basis."
But it's too early to reset the alarm clock just yet, said Kripke, an eight-hour-a-night sleeper. "Additional studies are needed to determine if setting your alarm clock earlier will actually improve your health."
Kripke and colleagues surveyed 1.1 million Americans aged 30 to 102 between 1982 and 1988. Participants were mainly friends and family of American Cancer Society volunteers, not randomly selected.
The results have not been available until recently, because of the time required to analyze the data.
The best survival rates were among people who slumbered seven hours a night — about 33 per cent of study participants. Those sleeping eight hours — about 38 per cent — were 12 per cent more likely than the first group to die within six years.
The increase in mortality was more than 15 per cent for those who reported getting more than 8.5 hours or less than four hours nightly.
Heart disease, stroke and cancer were the top causes of death.
Less than 1 per cent slept, like Napoleon, four hours or less. Eight per cent slept nine hours or more.
Frequent insomnia had no effect on risk of death, but taking a sleeping pill every night was associated with a 25 per cent increased risk.
The study provoked cautions, with some experts saying the main problem in sleep habits is deprivation.
"None of this says sleep kills people," Daniel Buysse, a University of Pittsburgh psychiatrist and past president of the American Academy of Sleep Medicine, told the Washington Post. "You should sleep as much as you need to feel awake, alert and attentive the next day ... I'm much more concerned about people short-changing themselves on sleep than people sleeping too long.''
The Star asked some high-profile Torontonians how much they sleep.
Robert Birgeneau, president of the University of Toronto, gets between 6 1/2 and 7 1/2 hours of sleep each night. He likes to get seven hours a night — so he's getting just what he needs.
"Usually, I don't get more than four hours," said Mayor Mel Lastman. "It hasn't always been that way. It started just about four years ago, when I got this job. I asked my doctor, and he said, `When you get out of politics, you'll find you will get a lot more sleep.' Occasionally, I do take something to help me sleep."
The idea that eight hours a night is optimal has been perpetuated by sleeping pill manufacturers, Kripke said. Sleep loss actually acts as an antidepressant, according to Kripke, who compared the habit of oversleeping to overeating. "Everyone knows that eating too much is bad for you. If you eat a little bit less than you desire, you will live longer. It is also true that if we look across the mammalian kingdom, the short sleepers live longer."
However, experts said the research fails to measure quality of sleep and neglects strong evidence that there are natural variations.
"Our approach is, you need as much sleep as it takes for you to wake up feeling refreshed. There's no set number. Some need more. Some need less, as long as it's good-quality, deep, restorative sleep," said Dr. Peter Munt, former sleep lab director at Kingston General Hospital.
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