Objective: To investigate the associations between use of Swedish moist smokeless tobacco (snus) and risk of Parkinson’s disease (PD).

Background: Cigarette smoking is associated with lower risk of PD. Use of snus leads to similar nicotine concentration in blood compared to cigarette smoking, but without combustion and yields of toxicants in tobacco smoke. Snus use can serve as a model to disentangle what constituent of tobacco smoke may cause the reduced PD risk.

Methods: We undertook pooled analyses of individual participant data from seven Swedish prospective studies, including 348,601 men. Outcome was first-ever PD diagnosis in national health registers. To assess study-specific relative risk of PD, we estimated hazard ratios (HRs) with 95% confidence intervals (CIs) using Cox proportional hazard regression models. The main analyses were restricted to never-smokers to eliminate the potential confounding effect of tobacco smoking on the association between snus use and PD risk.

Results: During a mean follow-up time of 16.1 years, 1,199 incident PD cases were identified. Among men who never smoked, ever-snus users had about 60 % lower PD risk compared to never-snus users (pooled HR 0.41, 95 % CI 0.28-0.61). The inverse association between snus use and risk of PD was more pronounced in current, heavy and long-term snus users. There was no evidence of heterogeneity between the studies.

Conclusions: Results from this large pooling project strongly support an inverse dose-response relationship between use of snus and subsequent risk of PD. Our results hence suggest a protective effect of nicotine on PD risk. Further research of the role of nicotine as a possible preventive agent in PD is warranted.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/moist-smokeless-tobacco-snus-use-and-risk-of-parkinsons-disease-meta-analysis-of-individual-participant-data-from-seven-prospective-observational-studies/