Association of Levels of Physical Activity With Risk of Parkinson Disease: A Systematic Review and Meta-analysis.

Importance: The association between physical activity and the risk of Parkinson disease (PD) has been increasingly recognized. However, to our knowledge, a comprehensive assessment of the quantitative dose-response association between physical activity and PD risk has not been performed previously. Objective: To quantify the dose-response association between physical activity and the risk of developing PD. Data Sources: PubMed, Embase, and Web of Science were systematically searched for peer-reviewed articles published through February 2018 reporting the association between physical activity and PD risk. Study Selection: Prospective studies that examined the association between physical activity and PD risk were included. Data Extraction and Synthesis: Data were extracted independently by 2 investigators. Adjusted risk estimates were extracted and pooled using a random-effects model. The study adhered to Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guidelines. Main Outcomes and Measures: The main outcome was the incidence of PD diagnoses confirmed by the treating neurologists or the authoritative medical records. Results: Eight prospective studies totaling 544 336 participants included 2192 patients with PD with a median (range) follow-up period of 12 (6.1-22.0) years were identified. A significantly reduced risk of PD was associated with the highest levels of either total physical activity (relative risk, 0.79; 95% CI, 0.68-0.91) or moderate to vigorous physical activity (relative risk, 0.71; 95% CI, 0.58-0.87), with stronger associations among men than among women. In contrast, light physical activity was not associated with PD risk (relative risk, 0.86; 95% CI, 0.60-1.23). The dose-response analysis revealed that for each 10 metabolic equivalent of task-hours/week increase in total or moderate to vigorous physical activity, the risk of PD among men decreased by 10% and 17%, respectively. No linear dose-response association was found between physical activity and PD risk among women. Conclusions and Relevance: This analysis revealed an inverse dose-response association between physical activity and PD risk among men; importantly, even moderate exercise was associated with a significant reduction in the risk of PD. Future studies with quantified measurements of physical activity will help identify the precise relative risk estimates for various levels of activity with respect to PD risk.