09 June 2011

Silent strokes less common in fit people

Adults who partake in moderate to vigorous exercise - equivalent to swimming or biking more than once per week - are 40% less likely to experience an asymptomatic stroke.


People who participate in vigorous activity are less likely to experience "silent" strokes, new study findings report.

Specifically, older adults who got the most exercise - equivalent to swimming or biking more than once per week - were 40% less likely to experience an asymptomatic stroke.

Even though these strokes are "silent," people who experience them are more at risk of other problems in the future, such as trouble with walking or mental functioning, as well as typical strokes, explained study author Dr Joshua Willey at Columbia University.

He and his colleagues found that people who engaged in less vigorous exercise - perhaps doing vigorous activity less frequently, or sticking with low-impact exercise such as golfing or bowling - were no less likely to experience asymptomatic cerebral infarcts.

Exercise and stroke risk

The study doesn't prove whether physical activity actually prevents stroke. People who participate in such activity may have other habits, or characteristics, that lower their risks.

Still, exercise is helpful for other reasons, Willey said.

"We know that light to moderate exercise helps with many other conditions. And we don't want our results to discourage our patients from doing exercise. Any is better than none, just in general, for overall health," Willey said. "And it seems to be, the more the better."

The study

During the study, Willey and his team at Columbia and the University of Miami interviewed more than 1,200 people 55 and older who had no symptoms of stroke and were already participating in a study on the risk of stroke about physical activity, then performed brain scans to check for brain infarcts.

Among the participants, who averaged 70 years of age at the time of their brain scan, 16% had experienced silent brain infarcts. Only those who engaged in the most activity had a reduced risk, the authors note in Neurology.

Surprising findings

It was somewhat surprising to see that people who engaged in less vigorous forms of exercise were not protected from silent strokes, said Willey.

"That throws us off a little bit."

Previous studies have also shown, however, that only moderate or heavy exercise appears to ward off stroke, he noted. In addition, only 36% of participants engaged in light exercise, and this may not be enough people to reveal a true impact, Willey added.

Physical activity had no relationship to the risk of another silent brain event, white matter hyperintensities (WMHs).

WMHs are also linked to later problems, such as dementia and trouble walking, as well as typical stroke, said  Willey. Researchers remain unclear about what causes WMHs, he noted, and something about the reasons for WMHs may explain the lack of relationship to exercise.

"We need to understand more what these white matter hyperintensities are we're witnessing."

Willey cautioned that this study only shows people who exercised heavily had a lower risk, not that exercise itself prevented silent strokes. In addition, he and his colleagues only measured physical activity by asking people what they did over the previous 2 weeks, and brain scans occurred several years after the exercise interview, which could have affected the findings.

He and his colleagues plan to look at relationships between brain scans and exercise in people who report their activity every year, he added. "We will look into that in the future." - (Alison McCook/Reuters Health, June 2011)

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