When all other risk factors are relatively equal, postmenopausal women who sleep between seven and eight hours each night are less likely to experience an ischemic attack, or stroke, than women of the same age group who sleep less than seven hours.  And women of this age group who sleep nine hours or more each night are at an even greater risk of experiencing a stroke than women who sleep less, according to the report of a study that has just been published in Stroke: Journal of the American Heart Association.

Getting nine hours or more of sleep each night raises a postmenopausal woman’s risk of stroke by as much as 60% to 70%, according to the study led by Jiu-Chiuan Chen, MD, ScD, an assistant professor of epidemiology at the School of Public Health, University of North Carolina, Chapel Hill.  His research team evaluated the link between sleep patterns and risk of stroke in 93,676 women age 50 to 79 between 1994 to 2005.  The women were patients at 40 clinics across the United States.

Some accompanying risk factors that were included in the Chen study include age, blood pressure, cholesterol levels, depression, diabetes, exercise, hormone replacement therapy (HRT), obstructive sleep apnea, and socioeconomic factors which included employment and household income.  The study participants’ sleep patterns were defined as follows:

• 8.3% slept five hours or less
• 26.9% slept six hours
• 37.5 slept seven hours
• 22.7% slept eight hours
• 4.0 slept nine hours
• 0.6% slept 10 hours or more

When all risk factors were considered and compared to the group getting seven hours of sleep, the findings revealed an increased risk of stroke per group as:

• 14% for those getting six hours of sleep or less
• 24% for those getting eight hours
• 70% for those getting nine hours or more

Other findings of the study include:

• Women who got the most sleep each night are more likely to be unemployed or retired; smokers; physically inactive; or they were diagnosed with cardiovascular disease, depression, diabetes, high cholesterol levels, or hypertension
• Women of minority ethnic groups, those who were overweight, and those undergoing HRT were more likely to sleep six hours of less
• Factors such as cardiovascular disease, depression, exercise, and income were found to influence sleep patterns but not to a degree that could explain the sleep/stroke association.

Citing many previous studies that have identified physiological consequences in people deprived of sleep, Chen says his team’s analysis could not clearly explain the increased risk of stroke for sleepers of short and long duration when all other lifestyle, medical, and psychosocial factors were evaluated.  Nor does this study imply any health benefits to cutting back on sleep in women who sleep nine or more hours each night, as undiagnosed disorders may be influencing a woman’s overall health.

Chen would like to see further studies done which weigh the value of sleep and risk for ischemic stroke and coronary heart disease, as this particular field of study has been rather limited thus far.

Chen’s study focused only on postmenopausal women ranging in age from 50 to 79 and he stresses the point that the findings of this study cannot be applied to younger women or to men of any age group.  It is unknown at this time if women of this particular age group may be more susceptible to the ill effects of sleeping too little or too much.

Source: American Heart Association