More evidence links exercise to lower stroke risk

Women who consistently get the minimum recommended amount of exercise for a healthy heart may be less likely to have a stroke than their counterparts whose exercise habits shift over time, a recent US study suggests. 

Researchers examined data on more than 61,000 women in the California Teachers Study who reported their exercise habits at two points in time, once from 1995 to 1996 and again from 2005 to 2006. The women were current and retired teachers when the study began. 

Overall, 987 women had a stroke by the end of the study period. 

But the women who got at least 150 minutes a week of moderate intensity exercise at both points in time were 30 per cent less likely to have what is known as an ischemic stroke, the most common kind, which occurs when a clot blocks an artery carrying blood to the brain. 

“How people exercise changes over time and some individuals exercise when they are a young adult but do not keep it up when they are older,” said lead study author Dr Joshua Willey of Columbia University Medical Centre in New York. 

“In our study, we found that maintaining exercise levels was protective against stroke, and that taking up exercise when not being active while younger was also protective,” Willey said by e-mail. “Similarly, those who no longer exercised on the follow up assessment did not have a lower risk of stroke.” 

The American Heart Association recommends that adults get at least 150 minutes a week of moderate-intensity exercise or at least 75 minutes of more vigorous physical activity. 

More than 22,000 women met these minimum recommendations at both points when they were assessed in the study, mostly with moderate exercise. 

Almost 19,000 women failed to get enough exercise at either point in time. 

Another 11,500 women fell short of this goal in the beginning but achieved it at the end, while about 8,600 women started out getting enough exercise, but failed to do so by the end of the study. 

Compared to women who failed to meet exercise recommendations at either point in time, women who got enough moderate activity at both points were 38 per cent less likely to have a fatal stroke and 12 per cent less likely to have any kind of stroke, the study found. 

Meeting moderate exercise guidelines by the end of the study, but not at the start, was associated with 35 per cent lower odds of a fatal stroke and 27 per cent lower odds of any stroke. 

But the chance of any stroke, including fatal ones, was similar for women who never got enough exercise and women who started out meeting the activity recommendations but did not do so at the end of the study, researchers report in the journal Stroke. 

The results were similar for women who did higher-intensity exercise. 

The study was not a controlled experiment designed to prove whether or how exercise habits might influence the odds of having a stroke or dying from it. 

Other limitations include the lack of data on other factors that could influence stroke risk such as blood pressure, obesity or diabetes, the authors note. 

Even so, the findings add to growing evidence for the benefits of moderate exercise, said Joe Northey of the University of Canberra in Australia. 

“Moderate intensity seems to be optimal for increasing blood flow to the brain,” Northey, who wasn’t involved in the study, said by e-mail. “Increasing cerebral blood flow through exercise improves the health and function of the brain.” 

Enjoyment, rather than intensity, should be the focus, said Dr James Burke, of the University of Michigan and the Ann Arbor, Virginia. 

“The best exercise is the one a person enjoys doing because he/she is more likely to make it a habit,” Burke, who was not involved in the study, said by email. 

Inactivity, meanwhile, can take a toll on health, said Sandra Billinger of Kansas University Medical Centre in Kansas City. 

“When we don’t exercise, our blood vessels become more stiff, we tend to gain weight, our lungs are not well used and our muscles become weak and lose size,” Billinger, who was not involved in the study, said by e-mail.