More than 5,000 people with no history of stroke participated in a three-year study. Results showed a greater incidence of stroke symptoms among those who slept less than six hours per night.

"In employed, middle-aged to older adults--relatively free of major risk factors for stroke such as obesity and sleep-disordered breathing-- short sleep duration may exact its own negative influence on stroke development," said Megan Ruiter, PhD, of the University of Alabama at Birmingham. "We speculate that short sleep duration is a precursor to other traiditional stroke risk factors."

Source

"Top Risk of Stroke for Normal-Weight Adults: Getting Under 6 Hours of Sleep," American Academy of Sleep Medicine, 6/11/12