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Thursday, 14 February, 2002, 20:03 GMT
Too much sleep 'is bad for you'
Person asleep
Six or seven hours sleep is better than eight
Eight hours' sleep a night has long been touted as the ideal length of time to spend under the duvet but new research suggests it could shorten your life.

A study that included more than a million participants found people who sleep eight hours or more died younger.

Those who only managed four or less hours in the land of nod were similarly affected but six or seven hours a night was found to be conducive to a longer life.

The research, carried out by scientists at the University of California, showed a clear association between long duration sleep and high mortality rates.

Individuals who now average 6.5 hours of sleep a night can be reassured this is a safe amount of sleep

Dr Daniel Kripke, study co-author
However, the research team cannot explain why this happens.

The report's author Dr Daniel Kripke, a professor of psychiatry, 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.

"Individuals who now average six-and-a-half hours of sleep a night can be reassured this is a safe amount of sleep.


The findings were being discussed at the annual meeting of the American Association for the Advancement of Science in Boston, Massachusetts.

Margaret Thatcher famously managed to function on just four hours' sleep a night.

Sleeping tablet danger

That may be too little, but people who managed as little as five hours a night lived longer than those who got more than eight hours.

The best survival rates were among those who slept seven hours a night, according a report published in the Archives of General Psychiatry.

Professor Jim Horne at Loughborough University's Sleep Research Centre said people who advocate the benefits of lots of sleep are misguided.

He said: "A lot of people can be reassured that six or seven hours sleep is okay.

Professor Jim Horne
Professor Horne: less is more
"The acid test for enough sleep is whether you are sleepy or alert throughout the day.

"If you are alert, then your sleep is probably adequate.

"However, nine hour sleepers shouldn't think they're going to die early."

The US study showed that a group sleeping eight hours were 12% more likely to die within the six year period covered by the study than those sleeping seven hours.

Between 1982 and 1988, a total of 5.1% of the women taking part and 9.4% of the men had died.

The study, involving 1.1million people was the first large-scale population study of sleep to take into account variables such as age, diet, exercise, previous health problems and risk factors such as smoking.

The study also found that occasional bouts of insomnia were not linked to higher death rates.

However, it concluded that people who take sleeping pills are more likely to die earlier.

See also:

15 Aug 00 | Health
Sleep linked to ageing
19 Jul 00 | Health
Sleep 'vital to update memory'
26 Apr 00 | Health
'Hormonal battle' controls sleep
10 Feb 00 | Health
Brain 'battles sleep deprivation'
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