Lifestyle Factors and Parkinson Disease Risk: Korean Nationwide Cohort Study With Repeated Health Screening Data

BACKGROUND AND OBJECTIVES: Many previous studies, mostly performed in Western countries, on the effects of lifestyle factors on Parkinson disease (PD) used baseline lifestyle characteristics without directly accounting for changes in covariate values over time. The objective of this study was to evaluate the association of repeatedly measured lifestyle factors with PD risk in a Korean population. METHODS: We conducted a nationwide population-based cohort study. Among 512,836 Koreans in the national health checkup database, we selected individuals who underwent health screening ≥3 times between 2002 and 2015 and followed up until December 31, 2015. PD was defined using the ICD-10 code G20 (with ≥3 times clinic visits for PD, to increase the diagnostic validity). Data on lifestyle factors such as smoking, alcohol consumption, and physical activity were collected using self-reported questionnaires. Logistic regression analysis with time-dependent covariates using generalized estimation equation models was performed to determine PD development. RESULTS: During the 14-year follow-up, 2,665 patients developed PD. Smoking showed a dose-response inverse association with PD only in men (ex-smoker, odds ratio [OR] 0.782, 95% confidence interval [CI] 0.713-0.858; current smoker, OR 0.556, 95% CI 0.488-0.632). Alcohol consumption and regular physical activity were related to reduced PD development in both sexes; however, alcohol consumption in men (≤3 per week, OR 0.717, 95% CI 0.658-0.780; ≥4 per week, OR 0.745, 95% CI 0.644-0.861) and physical activity in women (moderate, OR 0.792, 95% CI 0.748-0.840; vigorous, OR 0.830, 95% CI 0.756-0.911) had more consistent associations with PD development compared to those of the other sex. Participants with regular health screening showed a consistent relationship between lifestyle factors and PD development, whereas lifestyle factors in those without regular health screening had a decreased relationship with PD, even smoking habit. CONCLUSIONS: Analysis using repeatedly measured lifestyle factors showed an association between lifestyle factors and PD development. Characteristics of lifestyle data including repeated measurements, timing, or regularity might influence results, and future studies with appropriate lifestyle factors could increase PD risk prediction. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that smoking, alcohol use, and physical activity are associated with reduced risk of PD in a Korean population.