Abstract
The purpose of this study was to investigate associations between recreational physical activity and Parkinson's disease (PD) risk. We prospectively followed 143,325 participants in the Cancer Prevention Study II Nutrition Cohort from 1992 to 2001 (mean age at baseline = 63). Recreational physical activity was estimated at baseline from the reported number of hours per week on average spent performing light intensity activities (walking, dancing) and moderate to vigorous intensity activities (jogging/running, lap swimming, tennis/racquetball, bicycling/stationary bike, aerobics/calisthenics). Incident cases of PD (n = 413) were confirmed by treating physicians and medical record review. Relative risks (RR) were estimated using proportional hazards models, adjusting for age, gender, smoking, and other risk factors. Risk of PD declined in the highest categories of baseline recreational activity. The RR comparing the highest category of total recreational activity (men > or = 23 metabolic equivalent task-hours/week [MET-h/wk], women > or = 18.5 MET-h/wk) to no activity was 0.8 (95% CI: 0.6, 1.2; P trend = 0.07). When light activity and moderate to vigorous activity were examined separately, only the latter was found to be associated with PD risk. The RR comparing the highest category of moderate to vigorous activity (men > or = 16 MET-h/wk, women > or = 11.5 MET-h/wk) to the lowest (0 MET-h/wk) was 0.6 (95% CI: 0.4, 1.0; P trend = 0.02). These results did not differ significantly by gender. The results were similar when we excluded cases with symptom onset in the first 4 years of follow-up. Our results may be explained either by a reduction in PD risk through moderate to vigorous activity, or by decreased baseline recreational activity due to preclinical PD.