Doctors from the University of North Carolina examined the sleep habits of 90,000 post-menopausal women.
They found that women who slept more than nine hours per night had a 60 percent higher risk for the most common form of stroke.
Women who slept less than six hours per night had a 14 percent increased risk.
Researchers said it is possible the two factors have a common cause; they said hormonal differences that influence sleep patterns could also determine the risk of certain diseases, like stroke.
