A modest level of aerobic fitness can result in a major reduction of stroke-risk in both men and women.
The study was led by Steven Hooker, Ph.D., director of the Prevention Research Center at the University Of South Carolina Arnold School Of Public Health, Columbia, S.C.
"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. This study is the first to suggest that there may be a significant independent association between cardio respiratory fitness (CRF) and fatal and nonfatal stroke in men and nonfatal stroke in women," said Hooker.
Stroke is usually fatal, and claims about 150,000 lives and ranks as the No. 3 cause of death. Data on more than 60,000 people was analysed. It constituted 46,405 men and 15,282 women who participated in the Aerobics Center Longitudinal Study between 1970 and 2001 at the Cooper Aerobics Center in Dallas. The participants were aged 18 to 100 and free of known cardiovascular disease when they entered the study. They were followed for an average of 18 years and in this time, 863 people, 692 men and 171 women, had strokes.
At the time of entering the study, each participant underwent a test for measuring CRF in which they walked on a treadmill at increasing grade and/or speed till the time they reached their maximal aerobic capacity.
Men in the top quartile (25 pct) of CRF level had a 40 pct lower relative risk of stroke compared to men in the lowest quartile. This inverse relationship remained 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, he said.
In the case of women, those in the higher CRF level had a 43 pct lower relative risk than those in the lowest fitness level.
It was observed that the overall stroke risk dropped substantially at the moderate CRF level, with the protective effect continuing almost unchanged through higher fitness levels. That is equivalent to 30 minutes or more of brisk walking, or an equal aerobic activity, five days a week.
"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. Although stroke death rates have declined over the past few decades, the public health burden of stroke-related disabilities continues to be large and may even increase in coming years, as the population ages," said Hooker.
According to him, 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 that one of the study's limitations is that most of the participants were white, well-educated and middle-upper income and recommended that data should be collected from other populations.