Parkinson's disease among gardeners exposed to pesticides - a Danish cohort study

Abstract

Objective Several studies have found positive associations between exposure to pesticides and Parkinson's disease. As Danish gardeners have had frequent, intensive exposure to pesticides, the aim of this study was to investigate their risk for Parkinson's disease. Methods The cohort was comprised of 3124 male members of the Danish Union of Gardeners on 1 April 1975. Hospital register data were used to follow them for a primary diagnosis of Parkinson's disease during 1977-2008 and to calculate standardized hospitalization rate ratios (SHR) for this disease among gardeners and the general Danish population for comparison. Data from the Danish Cancer Registry were used to calculate standardized incidence rate ratios (SIR) for smoking-related cancers among gardeners and the general population. Results The SHR for Parkinson's disease among gardeners was close to that of the general population [1.14, 95% confidence interval (95% CI) 0.76-1.65]. In a birth cohort analysis, a downward trend was observed, with the highest risk among gardeners born before 1915 (SHR 1.55, 95% CI 0.77-2.77). The SIR for smoking-related cancers did not differ from that of the general population. Conclusion The results indicate a weak but dose-related association between exposure to pesticides and risk for Parkinson's disease; however, the results were based on 28 cases and the possibility of no association cannot be ruled out.