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Moderate Aerobic Fitness Levels May Cut Stroke Risk
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The study, expected to be presented Thursday at the American Stroke Association's International Stroke Conference in New Orleans, showed 30 minutes or more of brisk walking, or an equivalent aerobic activity, five days a week could lower stroke risk by about 40 percent.
Fitness has a protective effect regardless of the presence or absence of other stroke risk factors, including family history of cardiovascular disease, diabetes, high blood pressure, elevated cholesterol levels and high body mass index, study author Steven Hooker said in a prepared statement.
This study is the first to suggest there may be a significant independent association between cardiorespiratory fitness (CRF) and fatal and nonfatal stroke in men and nonfatal stroke in women, said Hooker, director of the Prevention Research Center at the University of South Carolina Arnold School of Public Health.
About 780,000 U.S. adults suffer a stroke each year, and stroke is a leading cause of serious, long-term disability in the United States, according to the American Stroke Association. About 150,000 people die from strokes annually, making it the nation's No. 3 cause of death.
Researchers analyzed data on more than 60,000 people -- 46,405 men and 15,282 women -- who participated in a long-term study at the Cooper Aerobics Center in Dallas between 1970 and 2001. The participants, aged 18 to 100 and free of known cardiovascular disease when they entered the study, were followed for an average of 18 years. During that time, 863 people -- 692 men and 171 women -- had strokes.
Upon entering the study, each participant took a test to measure cardiorespiratory fitness in which they walked on a treadmill at an increasing grade and/or speed until they reached their maximal aerobic capacity.
Men in the highest quartile (25 percent) of CRF had a 40 percent lower relative risk of stroke compared with men in the lowest quartile. That difference stayed constant even after adjusting for other factors such as smoking, alcohol intake, family history of cardiovascular disease, body-mass index (an estimation of body fatness), high blood pressure, diabetes and high cholesterol levels, Hooker said.
Among women, those with a higher cardiorespiratory fitness level had a 43 percent lower relative risk than those in the lowest fitness level.
The overall stroke risk dropped substantially at the moderate CRF level, with the protective effect persisting almost unchanged through higher fitness levels.
"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," Hooker said.
Physical activity is a major modifiable cardiovascular disease risk factor. Increasing the nation's CRF through regular physical activity could be a vital weapon to lower the incidence of stroke in men and women, he said.
One of the study's limitations is that most of the participants were white, well-educated and middle-upper income, Hooker said. He recommended that data be collected from other populations.
-- Kevin McKeever
SOURCE: American Heart Association/American Stroke Association, news release, Feb. 21, 2008
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