Renegade Neurologist

From Medscape

A new analysis of data from the Cancer Prevention Study II Nutrition Cohort, including more than 143,000 men and women, has shown a reduced risk of Parkinson’s disease (PD) associated with moderate to vigorous exercise.

No protective effect was seen with light exercise such as walking, the researchers, with first author Evan L. Thacker, from the Harvard School of Public Health, in Boston, Massachusetts, noted.

Parkinson’s disease is now thought to result from the confluence of multiple genetic, environmental, and behavioral factors, Thacker told Medscape in an interview. “The field of PD research is moving in the direction of trying to understand multiple factors at the same time, and hopefully this kind of work can be helpful from that perspective. It’s 1 piece of the puzzle.”

These findings will be presented at the 59th Annual Meeting of the American Academy of Neurology (AAN) and are among several studies released prior to their presentation by the AAN.

Multiple Risks

Three previous prospective studies with designs similar to this study have suggested that exercise may be related to a reduced risk for Parkinson’s disease, Thacker noted. “What our study adds to what’s already been done is that we have a large number of cases

over 400 PD cases, so that’s a lot of information to work with,” he said. In addition, this cohort included both men and women; only 1 of the previous studies had included women.

In this study, the researchers prospectively followed 63,348 men and 79,977 women in the Cancer Prevention Study II Nutrition Cohort from 1992 to 2001. Physical activity was estimated at baseline from the reported number of hours per week on average spent in light-intensity and moderate to vigorous activities.

Light-intensity activities, averaging 3.5 metabolic equivalents (METs), included walking and dancing; moderate to vigorous activities, averaging 4 to 7 METs, included jogging or running, lap swimming, tennis or racquetball, bicycling (or using a stationary bike), and aerobics and calisthenics.

Over follow-up, there were 413 incident cases of PD, confirmed by the treating physicians or medical record review. Rate ratios for PD were estimated using proportional hazard models and adjusting for age, sex, smoking, and other risk factors.

“Overall, risk of PD declined at high levels of physical activity,” the authors write. Compared with participants who reported no physical activity, those with the highest quartile for recreational activity

for men more than 25 MET-hours per week, for women greater than 18 MET-hours per week

had a reduced risk for PD.

When light activity and moderate to vigorous activity were considered separately, only moderate to vigorous activity was associated with the reduced risk for PD, the authors note. “Light activities like walking don’t seem to make any difference at all for whether people get Parkinson’s disease, but for the more vigorous activities

lap swimming, jogging, running, those kinds of things

people who participated at the highest level have about a 40% less risk of Parkinson’s compared with the people who didn’t do any activity or only walking or light activities,” Thacker said.

The results did not vary significantly by gender and were similar when they lagged exposure by 4 years.

However, they found no significant relationship between recreational activity at age 40 and PD risk. “If exercise truly does provide some protection against Parkinson’s disease, the protection may be relatively short-lived,” Thacker said in the AAN statement. One of the previous studies had shown activity in early adulthood was related to reduced PD risk, “so the jury’s still out on this one,” he said.

The mechanism connecting exercise and Parkinson’s disease risk has not been extensively studied to date in humans, Thacker said. However some animal work has suggested that exercise may increase levels of certain nerve growth factors and urate, both of which might have protective effects. However, he said, “it’s really too early to say for sure what the biological link may be

it requires a lot more work.”

An interventional trial of exercise to provide definitive evidence that it prevents PD would be difficult, he noted, but in the meantime, “considering all of the other benefits of exercise, it certainly doesn’t hurt to make sure you get some moderate or vigorous exercise several times a week.”