Occupational and recreational physical activity and Parkinson's disease in Denmark

Objectives This study aimed to examine whether occupational and physical activity (PA) at different ages contribute to Parkinson's disease (PD) risk in a large population-based case-control study in Denmark. Methods We identified 1828 PD patients from the Danish National Hospital Register and recruited 1909 gender and year of birth matched controls from the Danish Central Population Register. Occupational and leisure-time PA were determined from a job exposure matrix based on occupational history and self-reported leisure-time information. Results No association was found for occupational PA alone in men, but higher leisure-time PA (>= 5 hours/week of strenuous activities) in young adulthood (15-25 years) was associated with a lower PD risk (adjusted odds ratio (ORadj) 0.75, 95% confidence interval (95% CI) 0.62-0.90); men who engaged in high occupational and high leisure-time PA in young adulthood had the lowest PD risk (ORadj 0.58, 95% CI 0.41-0.81). Among women, inverse associations were found for occupation PA before age 50 (highest vs lowest, ORadj 0.75, 95% CI 0.55-1.06) and strenuous leisure-time PA after age 50 (ORadj 0.65, 95% CI 0.87-0.99); no clear pattern was seen for leisure and occupational PA combined. Conclusions We observed gender-specific inverse associations between occupational and leisure-time PA and PD risk; however, we cannot preclude reverse causation especially in older ages since PD has a long prodromal stage that might lead to a reduction of PA years before motor symptom onset and PD diagnosis.