Release Date: February 15, 2001
BUFFALO, N.Y. -- If you sleep more than eight hours a night, snore or regularly are drowsy during the day, you may be at an increased risk of stroke, UB researchers have found.
These results from the Western New York Stroke Screening Study, presented in Fort Lauderdale today at the American Stroke Association's 26th International Stroke Conference, showed that people who regularly slept more than eight hours a night had 9 percent more strokes than those who slept less.
Persons who regularly were sleepy during the day showed a 10 percent increase in stroke, compared to those who didn't experience daytime somnolence.
"We found that certain sleep characteristics -- such as sleeping for more than eight hours, the tendency to fall asleep during the day and the tendency to snore -- influence the likelihood of having a stroke," said Adnan I. Qureshi, assistant professor of neurosurgery affiliated with UB's Toshiba Stroke Research Center and lead author on the study.
"Individuals who snore severely or have trouble staying awake during the day should see a doctor to find out why. These may be signs of sleep apnea, which is associated with an increased risk of having a stroke."
Sleep apnea is a condition in which breathing stops briefly and repeatedly during sleep. The breathing abnormality often causes snoring and frequent awakening, as the sleeper quickly gasps for breath, and can lead to drowsiness during the day. The condition is recognized as a contributor to heart disease and stroke.
Qureshi and colleagues evaluated the association between snoring, sleep duration and daytime sleepiness with stroke and carotid-artery narrowing in 1,348 adults who participated in a stroke-screening program in Buffalo. Of the group, 6 percent had a previous stroke and 7 percent had carotid arteries that were significantly narrowed.
Participants answered a questionnaire on sleep habits and cardiovascular risk factors, were interviewed by a neurologist or neurosurgeon to determine history of stroke and underwent ultrasound testing on the carotid artery to determine arterial narrowing.
Results showed that the frequency of prior stroke or transient ischemic attacks (TIAs) -- temporary, stroke-like events that last for a short time -- was 14 percent among those who regularly slept eight hours or more a night, while the frequency was 5.4 percent among those who slept for six to eight hours or less. Like many strokes, TIAs are caused by a blocked blood vessel within or leading to the brain.
Among individuals who reported experiencing daytime drowsiness, 14 percent had suffered a stroke or TIA, compared to 4 percent of the participants who remained alert during the day.
The current research was prompted by an earlier, smaller study by Qureshi and colleagues showing that individuals who reported longer sleep and daytime drowsiness were more likely to experience a stroke during a 10-year follow-up period. The team thought that some of the differences might be attributable to the classic risk factors for heart disease and stroke: age, race, gender, cigarette smoking, high cholesterol, high blood pressure and diabetes, so they took these variables into consideration in this latest study.
The risk for stroke was independently and significantly associated with daytime sleepiness, average hours of sleep and nighttime snoring, Qureshi said.
"We know from the literature that these patterns are not just habits individuals can change," Qureshi said. "They are unconscious actions. These individuals should see a physician for evaluation."
Qureshi and his colleagues now are investigating the connection between sleep disruption and stroke, and are examining sleep patterns in relation to other diseases.
Additional researchers on the study were M. Fareed K. Suri, Mudit Sharma, Ghias A. Rana, Zulfiqar Ali, Lee R. Guterman and L. Nelson Hopkins, all of the UB Department of Neurosurgery and Toshiba Stroke Research Center.
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