FORT LAUDERDALE, Fla. (AHA) — Sleeping for more than eight hours a night, snoring and daytime drowsiness was asscociated with an increased risk for stroke, researchers reported at the American Stroke Association's 26th International Stroke Conference. The American Stroke Association is a division of the American Heart Association.

Researchers 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, New York. 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 and underwent ultrasound testing on the carotid artery to determine the arterial narrowing or history of stroke.

The frequency of prior stroke or transient ischemic attacks (TIAs) was 14 percent among those who reported routinely sleeping eight hours or more a night, while the frequency was 5.4 percent among those who slept for 6-8 hours and 5.4 percent for those who slept less than 6 hours, says the study's lead author Adnan I. Qureshi, M.D., assistant professor of neurosurgery at the State University of New York at Buffalo.

Transient ischemic attacks are temporary, stroke-like events that last for a short time. Like many strokes, TIAs are caused by a blocked blood vessel leading to or within the brain.

Of 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.

"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," says Qureshi. "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 certain sleep disorders such as 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. It can lead to drowsiness during the day. Sleep apnea is recognized as a contributor to heart disease and stroke.

Qureshi and colleagues conducted an earlier study using database information in which they found 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. They took these variables into consideration in their latest study and found that the risk for stroke was independently and significantly associated with daytime sleepiness, average hours of sleep and nighttime snoring, Qureshi says.

The participants were also examined for the presence of carotid artery stenosis, a build-up of fatty material leading to narrowing of the principal arteries to the neck and head. Carotid artery stenosis is itself an indicator of a higher risk of stroke.

After adjusting for the other variables, the researchers found no association between carotid artery stenosis and sleep duration, daytime sleepiness and snoring.

Thus, they conclude sleep pattern abnormalities are independently associated with stroke and TIA. Exactly how the disruptions contribute to stroke and TIA risk is still uncertain. Underlying factors, such as depression or sleep apnea, may contribute to the chain of events.

Study participants were not asked to distinguish between sleep patterns before and after stroke. But the researchers assumed it was unlikely the strokes and TIAs caused major disruptions in habit because none were disabling. All were able to attend the stroke screening program at the Buffalo clinic where the study interviews took place in 1999 and 2000.

"We know from the literature that these patterns are not just habits individuals can change; they are unconscious actions," he says. "These individuals should see a physician for evaluation."

Qureshi and his colleagues are using the database again to investigate why sleep disruption contributes to stroke and to examine sleep patterns in relation to other diseases. These studies are in the preliminary stages.

Co-authors of the study are M. Fareed K. Suri, M.D.; Mudit Sharma, M.S.; Ghias A. Rana, M.D.; Zulfiqar Ali, M.D.; Lee R. Guterman, M.D.; and L.N. Hopkins, M.D.