BACKGROUND: Previous studies showed that lifestyle behaviors (cigarette smoking, alcohol, coffee) are inversely associated with Parkinson's disease (PD). The prodromal phase of PD raises the possibility that these associations may be explained by reverse causation. OBJECTIVE: To examine associations of lifestyle behaviors with PD using two-sample Mendelian randomisation (MR) and the potential for survival and incidence-prevalence biases. METHODS: We used summary statistics from publicly available studies to estimate the association of genetic polymorphisms with lifestyle behaviors, and from Courage-PD (7,369 cases, 7,018 controls; European ancestry) to estimate the association of these variants with PD. We used the inverse-variance weighted method to compute odds ratios (ORIVW) of PD and 95%confidence intervals (CI). Significance was determined using a Bonferroni-corrected significance threshold (p = 0.017). RESULTS: We found a significant inverse association between smoking initiation and PD (ORIVW per 1-SD increase in the prevalence of ever smoking = 0.74, 95%CI = 0.60-0.93, p = 0.009) without significant directional pleiotropy. Associations in participants ≤67 years old and cases with disease duration ≤7 years were of a similar size. No significant associations were observed for alcohol and coffee drinking. In reverse MR, genetic liability toward PD was not associated with smoking or coffee drinking but was positively associated with alcohol drinking. CONCLUSION: Our findings are in favor of an inverse association between smoking and PD that is not explained by reverse causation, confounding, and survival or incidence-prevalence biases. Genetic liability toward PD was positively associated with alcohol drinking. Conclusions on the association of alcohol and coffee drinking with PD are hampered by insufficient statistical power.
FörderungenUK Medical Research Council (CEC, KEM) NRF-DST Centre of Excellence for Biomedical Tuberculosis Research Stellenbosch University, South Africa South African Medical Research Council (Self-Initiated Research Grant) National Research Foundation of South Africa Italian Ministry of Health (Ricerca Corrente 2021) Estonian Research Council MSWA Canadian Consortium on Neurodegeneration in Aging Department of Health and Human Services Intramural Research Program of the National Institute on Aging Michael J Fox Foundation (USA Genetic Diversity in PD Program: GAP-India) MSA Coalition German Research Council South African Medical Research Council Centre for Tuberculosis Research Division of Molecular Biology and Human Genetics Faculty of Medicine and Health Sciences Parkinson's UK. PG GEN sample collection - MRC Karolinska Institutet Research Funds Karolinska Institutet Research Fund Swedish Brain Foundation Marta Lundkvist Foundation National Institutes of Health Swedish Research Council Spanish Ministry of Science and Innovation Cape Town Stellenbosch University EU Joint Program for Neurodegenerative Disease research (JPND)