Occupational exposure in parkinsonian disorders: a 43-year prospective cohort study in men

Background: Several occupations and occupational exposures have been investigated for associations with Parkinson's disease. Common findings are increased risk associated with pesticide exposure and no association between Parkinson's disease and welding.

Methods: We explored the association between a broad range of possible occupational risk factors and Parkinson's disease as well as Parkinson's disease plus other forms of Parkinsonism (referred to as Parkinsonian disorders), using prospectively collected data in the population-based Swedish Twin Registry. A cohort of 14,169 Swedish men was followed for up to 43 years. We identified 234 Parkinsonian disorder cases including 204 Parkinson's disease cases with complete data. We assessed exposure to 14 chemical and biological compounds through a job exposure matrix. Hazard ratios (HR) with 95% confidence intervals (CI) adjusted for age, smoking, and education were used to estimate the relative risk of disease associated with exposure.

Results: Exposure to inorganic dust was associated with increased risk of Parkinson's disease and Parkinsonian disorders, HR 1.6 (95% CI 1.1-2.4) and 1.5 (1.0-2.2) respectively. There was no association between Parkinson's disease or Parkinsonian disorders and occupational exposure to pesticides, welding smoke, metal dust, wood dust, animal handling, stone and concrete dust, chrome and nickel dust, quartz dust, organic dust, oil, asbestos, organic solvents and irritating gas.

Conclusions: Inorganic dust should be explored further as a potential risk factor for Parkinson's disease. Occupational exposure to pesticides and twelve other compounds explored in this study may not be associated with risk of Parkinson's disease in Swedish men.