Habitually sleeping less than six hours significantly increases stroke risk among middle-age to older adults of normal weight and at low risk for sleep apnea, study of 5,666 people followed for up to three years reports. Participants started with no stroke history or high risk for sleep apnea, BMI was adjusted for. First stroke symptoms were measured, along with demographic information, stroke risk factors, depression symptoms, health behaviors. Study found no association among overweight participants.