From: Karin Zeitvogel, Discovery News
Published August 10, 2010 10:43 AM

7 Hours Sleep Just Right

People who sleep more or fewer than seven hours a day, including naps, are increasing their risk for cardiovascular disease, the leading cause of death in the United States, a study published Sunday shows.

Sleeping fewer than five hours a day, including naps, more than doubles the risk of being diagnosed with angina, coronary heart disease, heart attack or stroke, the study conducted by researchers at West Virginia University's (WVU) faculty of medicine and published in the journal Sleep says.

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And sleeping more than seven hours also increases the risk of cardiovascular disease, it says.

Study participants who said they slept nine hours or longer a day were one-and-a-half times more likely than seven-hour sleepers to develop cardiovascular disease, the study found.

The most at-risk group was adults under 60 years of age who slept five hours or fewer a night. They increased their risk of developing cardiovascular disease more than threefold compared to people who sleep seven hours.

Women who skimped on sleep, getting five hours or fewer a day, including naps, were more than two-and-a-half times as likely to develop cardiovascular disease.

Short sleep duration was associated with angina, while both sleeping too little and sleeping too much were associated with heart attack and stroke, the study says.

A separate study, also published in Sleep, showed that an occasional long lie-in can be beneficial for those who can't avoid getting too little sleep.

In that study, David Dinges, who heads the sleep and chronobiology unit at the University of Pennsylvania school of medicine, found that 142 adults whose sleep was severely restricted for five days -- as it is for many people during the work week -- had slower reaction times and more trouble focusing.

But after a night of recovery sleep, the sleep-deprived study participants' alertness improved significantly, and the greatest improvements were seen in those who were allowed to spend 10 hours in bed after a week with just four hours' sleep a night.

Article continues: http://news.discovery.com/human/sleep-seven-hours.html#mkcpgn=rssnws1

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