Solvent exposed occupations and risk of Parkinson disease in Finland

• Published in: Clinical parkinsonism & related disorders Vol. 4; p. 100092
• Main Authors: Nielsen, Susan Searles, Warden, Mark N., Sallmén, Markku, Sainio, Markku, Uuksulainen, Sanni, Checkoway, Harvey, Hublin, Christer, Racette, Brad A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2021; Elsevier
• Subjects: 1,1,1-trichloroethane; Methylene chloride; Original; Parkinson disease; Solvents; Trichloroethylene; Parkinson disease; Trichloroethylene; Solvents; 1,1,1-trichloroethane; Methylene chloride
• ISSN: 2590-1125; 2590-1125
• DOI: 10.1016/j.prdoa.2021.100092

•Finnish register-based case-control Parkinson disease (PD) studies are feasible.•Some occupations with potential for exposure to solvents are associated with PD.•Chlorinated hydrocarbon solvents in particular might increase PD risk modestly.•Some occupational co-exposures might enhance PD-solvent associations in PD studies.•Studies without smoking/education data will underestimate PD-solvent associations. Epidemiologic and toxicology studies suggest that exposure to various solvents, especially chlorinated hydrocarbon solvents, might increase Parkinson disease (PD) risk. In a population-based case-control study in Finland, we examined whether occupations with potential for solvent exposures were associated with PD. We identified newly diagnosed cases age 45–84 from a nationwide medication reimbursement register in 1995–2014. From the population register, we randomly selected non-PD controls matched on sex, along with birth and diagnosis years (age). We included 11,757 cases and 23,236 controls with an occupation in the 1990 census, corresponding to age 40–60. We focused on 28 occupations with ≥ 5% probability of solvent exposure according to the Finnish Job Exposure Matrix. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) by logistic regression modeling, adjusting for age, sex, socioeconomic status, and smoking probability. Similar proportions of cases (5.5%) and controls (5.6%) had an occupation with potential exposure to any solvents. However, all occupations with a point estimate above one, and all significantly or marginally significantly associated with PD (electronic/telecommunications worker [OR = 1.63, 95% CI 1.05–2.50], laboratory assistant [OR = 1.40, 95% CI 0.98–1.99], and machine/engine mechanic [OR = 1.23, 95% CI 0.99–1.52]) entailed potential for exposure to chlorinated hydrocarbon solvents, specifically. Secondary analyses indicated exposure to polycyclic aromatic hydrocarbons and some metals might contribute to the association for mechanics. PD risk might be slightly increased in occupations with potential exposure to chlorinated hydrocarbon solvents. Confirmation is required in additional studies that adjust for other occupational exposures and smoking.