April 23, 2007 -- People who exercise regularly may be less likely to develop Parkinson's disease -- but leisurely strolls may not be enough.
That news comes from a study of more than 143,300 U.S. men and women who were followed from 1992-2001.
When the study started, participants were 63 years old, on average. They reported their weekly hours of light exercise (walking or dancing) and moderate to vigorous exercise (jogging, running, swimming, bicycling, playing tennis or racquetball, or doing aerobics or calisthenics).
A total of 413 participants were diagnosed with Parkinson's disease by the end of the study.
The most active participants were the least likely to develop Parkinson's disease in the next decade, according to the researchers, who included Evan Thacker, SM, of Harvard School of Public Health.
Exercise and Parkinson's
"The most important thing we learned from this study was that high levels of moderate to vigorous recreational physical activity (like biking, swimming, aerobics, etc.) were associated with lower Parkinson's disease risk," Thacker tells WebMD.
"Those with the highest levels of recreational physical activity at the beginning of the study had a lower risk of getting Parkinson's disease over the next 10 years, compared to the people with low levels of recreational physical activity or none at all," says Thacker.
Thacker will present the study in Boston on May 1, 2007 at the American Academy of Neurology's 59th annual meeting.
How Much Exercise?
The drop in Parkinson's disease risk was only seen in people who got a lot of moderate to vigorous exercise.
"People who reported the highest levels of recreational physical activity in the study were doing about the equivalent of 5-6 hours of aerobics or 3-4 hours of lap swimming each week ," says Thacker.
"Their Parkinson's disease risk was 40% lower than the people who reported zero physical activity, or only light activities like walking," he says.
Exercise Intensity Mattered
"Light physical activity such as walking or dancing was not related to Parkinson's disease risk at all," says Thacker.
"On the other hand," he says, "higher participation in moderate to vigorous activities such as biking, lap swimming, jogging, etc., was associated with lower Parkinson's disease risk."
No particular form of moderate to vigorous exercise stood out as being best.
"The amount of time spent and the overall level of intensity were more important than the specific activity," says Thacker.
The study was purely observational. That is, participants weren't asked to exercise.
The researchers considered participants' age, gender, and smoking -- but they can't rule out the possibility that other factors influenced the results.
Thacker and colleagues aren't blaming Parkinson's disease on insufficient exercise. Their study also doesn't promise that exercise will prevent Parkinson's disease.
Many factors may affect the odds of developing Parkinson's disease, and doctors often don't know precisely why someone develops Parkinson's disease.
"Our study is just one piece in a complicated puzzle of discovering what might prevent Parkinson's disease," says Thacker.