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Objective We studied the relation between Parkinson disease (PD) and professional exposure to pesticides in a community-based case-control study conducted in a population characterized by a high prevalence of exposure. Our objective was to investigate the role of specific pesticide families and to perform dose-effect analyses. Methods PD cases (n = 224) from the Mutualite Sociale Agricole (France) were matched to 557 controls free of PD affiliated with the same health insurance. Pesticide exposure was assessed using a 2-phase procedure, including a case-by-case expert evaluation. Analyses of the relation between PD and professional exposure to pesticides were first performed overall and by broad category (insecticides, fungicides, herbicides). Analyses of 29 pesticide families defined based on a chemical classification were restricted to men. Multiple imputation was used to impute missing values of pesticide families. Data were analyzed using conditional logistic regression, both using a complete-case and an imputed dataset. Results We found a positive association between PD and overall professional pesticide use (odds ratio [OR] = 1.8, 95% confidence interval [CI] = 1.1–3.1), with a dose-effect relation for the number of years of use (p = 0.01). In men, insecticides were associated with PD (OR = 2.2, 95% CI = 1.1–4.3), in particular organochlorine insecticides (OR = 2.4, 95% CI = 1.2–5.0). These associations were stronger in men with older onset PD than in those with younger onset PD, and were characterized by a dose-effect relation in the former group. Interpretation Our results support an association between PD and professional pesticide exposure, and show that some pesticides (ie, organochlorine insecticides) may be more particularly involved. Ann Neurol 2009;66:494–504

We studied the relation between Parkinson disease (PD) and professional exposure to pesticides in a community-based case-control study conducted in a population characterized by a high prevalence of exposure. Our objective was to investigate the role of specific pesticide families and to perform dose-effect analyses.PD cases (n = 224) from the Mutualité Sociale Agricole (France) were matched to 557 controls free of PD affiliated with the same health insurance. Pesticide exposure was assessed using a 2-phase procedure, including a case-by-case expert evaluation. Analyses of the relation between PD and professional exposure to pesticides were first performed overall and by broad category (insecticides, fungicides, herbicides). Analyses of 29 pesticide families defined based on a chemical classification were restricted to men. Multiple imputation was used to impute missing values of pesticide families. Data were analyzed using conditional logistic regression, both using a complete-case and an imputed dataset.We found a positive association between PD and overall professional pesticide use (odds ratio [OR] = 1.8, 95% confidence interval [CI] = 1.1-3.1), with a dose-effect relation for the number of years of use (p = 0.01). In men, insecticides were associated with PD (OR = 2.2, 95% CI = 1.1-4.3), in particular organochlorine insecticides (OR = 2.4, 95% CI = 1.2-5.0). These associations were stronger in men with older onset PD than in those with younger onset PD, and were characterized by a dose-effect relation in the former group.Our results support an association between PD and professional pesticide exposure, and show that some pesticides (ie, organochlorine insecticides) may be more particularly involved.