Dozing In The Day Linked To Higher Stroke Risk In Elderly

A new US study found that dozing during the day could be a sign of increased stroke risk for elderly Americans. The findings of the study (Abstract 94) were presented to the American Stroke Association's International Stroke Conference 2008, taking place in New Orleans this week.

The researchers found that stroke risk was two to four times greater in elderly people who dozed moderately during the day. Dozing was defined as "unintentionally falling asleep".

Research has already indicated that apnea, where breathing stops for brief periods during sleep, is linked to higher stroke risk, and that daytime drowsiness could be a result of poor night sleep due to apnea.

Lead author, Dr Bernadette Boden-Albala, assistant professor of neurology at the College of Physicians and Surgeons, Columbia University, New York City, said the results suggest that:

"Daytime dozing may be an important and novel stroke risk factor."

Boden-Albala and colleagues studied data from a community based cohort comprising 2,153 participants taking part in the NOMAS Northern Manhattan (prospective) Study that started in 1990. This is the first study to look into stroke risk for whites, blacks and Hispanics living in the same community.

None of the participants had suffered a stroke when they enrolled. Their average age was 73 and 64 per cent were women, 60 per cent were Hispanic, 20 per cent were black and 18 per cent were white.

The researchers began collecting data on daytime dozing in 2004, using a survey based instrument called the Epworth Sleepiness Scale, which asked participants to rate the frequency of their dozing in specific circumstances, for example while watching TV, sitting and chatting to someone, stopping briefly in traffic while driving, and sitting quietly after a lunch with no alcohol.

The results showed that:

• 44 per cent of the participants fell into the "no dozing" category; 47 per cent were in the "some dozing" category; and 9 per cent fell into the "significant dozing" category.


• Over an average follow-up of 2.3 years, there were 40 strokes and 127 vascular events such as heart attack or stroke death caused by vascular problems among the participants.


• The risk of stroke was 2.6 times greater for those participants who were doing "some dozing" compared to those who did "no dozing".


• Those in the "significant dozing" group showed a 4.5 times greater risk.


• There were no unexpectedly high stroke risks for the two dozing groups compared to the no dozing group after controlling for several stroke risk factors: race-ethnicity, age, gender, education, diabetes, blood pressure, obesity and physical activity.


• The risk of a heart attack or vascular death was 1.6 per cent higher for the "some dozing" group, and 2.6 percent for the "significant dozing" group, and this was similar for both men and women and all ethnicities.

"Those are significant numbers," said Boden-Albala, "we were surprised that the impact was that high for such a short period of time."

"Given what's known now, it's worth assessing patients for sleep problems", she said, adding that, "the initial assessment can be something as simple as the Epworth scale. If patients are moderately or significantly dozing, physicians need to think about sending them for further evaluation," she suggested.

If confirmed by other studies, these results could have important implications for public health. If studies show we are not getting enough sleep, then the real question, Boden-Albala asked, is:

"what are we doing to our bodies? Sleepiness obviously puts us at risk of stroke."

Another stroke study on 60,000 people, that was presented at the same conference by Steven Hooker of the University of South Carolina and colleagues, suggested that moderate aerobic fitness protected people from stroke, even if they had higher risk of heart disease or diabetes, Reuters reported.

Hooker told the press:

"We found that a low-to-moderate amount of aerobic fitness for men and women across the whole adult age spectrum would be enough to substantially reduce stroke risk."

Stroke is the third leading cause of death among Americans, after heart disease and cancer. About 780,000 adults have a stroke every year in the US, and of these, 150,000 die from one.