title: Moist smokeless tobacco (Snus) use and risk of Parkinson's disease.
abstract: Cigarette smoking is associated with a lower risk of Parkinson's disease. It is unclear what constituent of tobacco smoke may lower the risk. Use of Swedish moist smokeless tobacco (snus) can serve as a model to disentangle what constituent of tobacco smoke may lower the risk. The aim of this study was to determine whether snus use was associated with a lower risk of Parkinson's disease.
  
  
  
  Individual participant data were collected from seven prospective cohort studies, including 348 601 men. We used survival analysis with multivariable Cox regression to estimate study-specific relative risk of Parkinson's disease due to snus use, and random-effects models to pool estimates in a meta-analysis. The primary analyses were restricted to never-smokers to eliminate the potential confounding effect of tobacco smoking.
  
  
  
  During a mean follow-up time of 16.1 years, 1199 incident Parkinson's disease cases were identified. Among men who never smoked, ever-snus users had about 60% lower Parkinson's disease risk compared with never-snus users [pooled hazard ratio (HR) 0.41, 95% confidence interval (CI) 0.28-0.61]. The inverse association between snus use and Parkinson's disease risk was more pronounced in current (pooled HR 0.38, 95% CI 0.23-0.63), moderate-heavy amount (pooled HR 0.41, 95% CI 0.19-0.90) and long-term snus users (pooled HR 0.44, 95% CI 0.24-0.83).
  
  
  
  Non-smoking men who used snus had a substantially lower risk of Parkinson's disease. Results also indicated an inverse dose-response relationship between snus use and Parkinson's disease risk. Our findings suggest that nicotine or other components of tobacco leaves may influence the development of Parkinson's disease.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Fei
authors.initials: F
authors.lastname: Yang
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.|Department of Psychology, University of Southern California, Los Angeles, CA, USA.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Pedersen
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Weimin
authors.initials: W
authors.lastname: Ye
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Epidemiology and Global Health, Department of Public Health and Clinical Medicine.
authors.forename: Margareta
authors.initials: M
authors.lastname: Norberg
authors.affiliation: Department of Pharmacology and Clinical Neuroscience, Umeå University, Umeå, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Forsgren
authors.affiliation: Department of Medicine, Clinical Epidemiology Unit.|Department of Endocrinology, Metabolism and Diabetes, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Ylva
authors.initials: Y
authors.lastname: Trolle Lagerros
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.|Department of Statistics and Quantitative Methods, University of Milano-Bicocca, Milan, Italy.
authors.forename: Rino
authors.initials: R
authors.lastname: Bellocco
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
authors.affiliation: Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Knutsson
authors.affiliation: Department of Public Health and Clinical Medicine, Skellefteå Research Unit.
authors.forename: Jan-Håkan
authors.initials: JH
authors.lastname: Jansson
authors.affiliation: Department of Public Health and Clinical Medicine, Family Medicine, Umeå University, Umeå, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Wennberg
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.|Centre for Epidemiology and Community Medicine, Stockholm County Council, Stockholm, Sweden.
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Galanti
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.|Centre for Epidemiology and Community Medicine, Stockholm County Council, Stockholm, Sweden.
authors.forename: Anton C J
authors.initials: ACJ
authors.lastname: Lager
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Marzieh
authors.initials: M
authors.lastname: Araghi
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Lundberg
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.|Centre for Epidemiology and Community Medicine, Stockholm County Council, Stockholm, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Magnusson
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.|Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Wirdefeldt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010300:Parkinson Disease / Q000453:epidemiology*; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D057566:Self Report; D013548:Sweden / Q000453:epidemiology; D064424:Tobacco Use / Q000453:epidemiology*; D014030:Tobacco, Smokeless
keywords: Parkinson’s disease; epidemiology; individual participant data; nicotine; risk factors