Five hours' sleep is enough, study finds - Not getting seven or eight hours of sleep a night won't kill you, new research shows. Earlier this year a large-scale study indicated that getting less than seven hours' sleep was associated with an increased risk of heart disease. Another concluded that people who sleep less than six hours a night are more likely to die before the age of 65.
Getting as little as five hours' sleep is fine, a US study has found
But a new report, which followed almost 450 middle-aged and elderly women over a 14-year period, found that those who slept between five and six-and-half hours were most likely to still be alive.
It differed from other studies in that it measured sleep using wrist activity monitors, rather than asking people about their sleep habits.
Daniel Kripke, professor emeritus of psychiatry at the University of California San Diego School of Medicine, said: "The surprise was that when sleep was measured objectively, the best survival was observed among women who slept five to 6.5 hours.
"Women who slept less than five hours a night or more than 6.5 hours were less likely to be alive at the 14-year follow-up."
The findings are published online in the journal Sleep Medicine.
Prof Kripke said the study should allay some people's fears that they were not getting enough sleep.
"This means that women who sleep as little as five to six-and-a-half hours have nothing to worry about since that amount of sleep is evidently consistent with excellent survival," he said.
He added that getting between five and six-and-a-half hours sleep was the average for the sample of San Diego women in the study.
In March, a British study of 3,000 people found the average Briton sleeps for six hours a night.
The question of why sleep is essential has vexed researchers for decades.
It is now known that it helps the body to maintain itself in numerous ways, like enabling cells to repair.
Sleep deprivation is known to raise blood pressure and reduce glucose tolerance, which can both increase the risk of artery damage.
Those who do not sleep enough have also been shown to eat more and be less attractive than people who do. ( telegraph.co.uk )