Obstructive sleep apnea is associated with an increased risk of stroke in middle-aged and older adults, especially men, according to new results from a landmark study supported by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health. Overall, sleep apnea more than doubles the risk of stroke in men. Obstructive sleep apnea is a common disorder in which the upper airway is intermittently narrowed or blocked, disrupting sleep and breathing during sleep.