Sleep Habits Among Postmenopausal Women Can Increase Stroke Risk

A new Catch-22 for postmenopausal women: Sleeping too much can cause a serious increase in the risk of stroke, while sleeping too little may raise stroke risk to a lesser degree. So what is the optimal amount of sleep for women in this category?
Researchers found that postmenopausal women who regularly sleep nine or more hours are 70 percent more likely to suffer an ischemic stroke than women who sleep an average of seven hours per night. In addition, researchers discovered that women who sleep six hours or less nightly have a 14 percent greater risk of stroke in comparison to those who sleep seven hours a night.

An ischemic stroke is the most common type of stroke, accounting for about 83 percent of all stroke cases. Ischemic strokes occur as a result of blockage within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls.

Although the new findings are only valid for the postmenopausal women in the study, some experts theorize that same relationship between sleep and stroke risk may apply in general. The study was led by Dr. Jiu-Chiuan Chen, an assistant professor of epidemiology at the University of North Carolina School of Public Health and included more than 93,000 women ages 50 to 79 years of age. The research participants were patients at 40 clinics across the United States from 1994 to 2005.

Over the course of the study, there were 1,166 cases of ischemic stroke with an average follow-up time of 7.5 years. The findings accounted for age, race, socioeconomic status, depression, smoking, exercise, use of hormone therapy, (HRT) and cardiovascular risk factors such as past history or stroke or heart attack, high blood pressure, and diabetes. Women who slept seven hours a night were found to have he lowest risk for stroke. About twice as many women reported sleeping less than six hours nightly—8.3 percent, compared to those who sleep nine hours or more—4.6 percent.

In other findings, women getting the most sleep each night are more likely to be unemployed or retired. They may be physically inactive, suffer from depression, or have cardiovascular disease, diabetes, high cholesterol, or hypertension. Smokers are also among those who sleep more. Women who are overweight, undergoing HRT and belonging to minority ethnic groups are more likely to sleep six hours or less.

Chen said that his team's analysis does not explain the increased risk of stroke for those with too long or too short sleeping patterns when evaluating other lifestyle, medical, and psychosocial factors. Additionally, the study does not indicate there are health benefits to be gained from cutting back sleep from nine or more hours each night, or getting more than six hours since undiagnosed disorders could be affecting a woman's overall health. Chen would like to see further studies conducted to analyze the relationship between sleep and risk for ischemic stroke and coronary heart disease.

The study and its findings appear online in Stroke: Journal of the American Heart Association.