Background Prior epidemiologic and animal studies indicate that occupational exposure to solvents, particularly trichloroethylene, may increase risk of Parkinson disease (PD).
Methods We constructed a population-based case-control study of incident PD in Finland using a medication database maintained by the Social Insurance Institution of Finland, along with the Population Information System, which includes census records for all Finnish residents. PD cases were diagnosed (first approved to receive PD medications) between 1995–2014. We randomly selected controls from the underlying population while matching on diagnosis year, birth year (1930–1950), and sex. Individual occupational census data from 1990, allowing for a minimum of five years of exposure lagging, were available for 11,757 PD cases and 23 236 controls. These data were linked to the Finnish Job Exposure Matrix (FINJEM) to identify potential for occupational exposure to four classes of solvents. We estimated PD-solvent odds ratios (ORs) and 95% confidence intervals (CIs) using unconditional logistic regression, while adjusting for matching variables and socioeconomic status as a proxy for tobacco smoking.
Results Cases and controls were age 45–89 years at diagnosis/reference and age 40–60 years at occupational exposure assessment. There was no evidence that PD was associated with occupational exposure to solvents overall (19% cases and 20% controls), or to aromatic hydrocarbon solvents in particular, with ORs very close to null. In contrast, there was a modestly higher PD risk in relation to exposure to chlorinated hydrocarbon solvents, most notably trichloroethylene (OR=1.11, 95% CI: 0.98 to 1.26). Occupation as a mechanic (OR=1.20, 95% CI: 0.97 to 1.49) or as an electronic or telecommunications worker (OR=1.65, 95% CI: 1.07 to 2.54) contributed to this association.
Conclusion Consistent with prior literature, occupational exposure to tricholoethylene may at least modestly increase risk of PD.
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