Monday, September 22, 2008

What Is the Link Between Sleep Duration and Stroke?

I used to hear from friends or relatives that one should sleep at least 8 hours per night to stay healthy. Is this a justified statement? Does it mean that we should sleep as long as we can?

In reality, “the more is better” may not be true, at least not for the sleep duration.

A report published in July 2008 in the medical journal “Stroke” indicated that middle-aged women who slept 9 hours or more per night would have their risk of stroke increased by 70 percent. This is the finding obtained by United States researchers from the University of North Carolina in Chapel Hill.

Although a number of studies have established a link between sleep duration and mortality, there is still a lack of evidence to associate sleep patterns and cardiovascular disease.

Of the 93,175 women of age between 50 and 79, who were enrolled in the Women’s Health Initiative Study, 8.3 per cent normally slept no more than 5 hours per night, while 4.6 percent slept at least 9 hours per night.

At the end of the study (span over a period of average of 7.5 years), it was found that 1,166 women got ischemic stroke. This is the most common type of stroke, which occurs when blood vessels in the brain block. When this happens, oxygen will be prevented from reaching the brain and will thus cause the brain's tissue to die.

When comparing with women sleeping 7 hours, those slept 6 hours or less, 8 hours, or 9 hours or more increased the risk of stroke by 14 percent, 24 percent, and 70 percent, respectively.

For women who slept 6 hours or less and had cardiovascular disease at the beginning of the study, their chance of getting stroke was increased by 22 percent. Furthermore, women who slept longer hours during the night were not associated with frequent snore or sleepiness. Therefore, sleep during, either shorter or longer than the norm (7 hours), could be independent risk factors for stroke.

Women sleeping long hours during the night is not so common than those who slept less than 6 hours, therefore, the overall health impact of a short sleep is probably greater than long sleep.

However, the researchers caution that their data do not imply that women of long sleep duration would cut their risk of stroke if they reduce their sleep duration. Further studies are still required to help understand the possible mechanisms behind the associations found in this study.

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