[Note: the organochlorine insecticides  that this study of farmers implicates particularly in Parkinson’s are very persistent in the environment and the body. DDT is one of them.]
Objective: We studied the relation between Parkinson's 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 (MSA, France) were matched to 557 controls free of PD affiliated to the same health insurance. Pesticide exposure was assessed using a two-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.
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• We found a positive association between PD and overall professional pesticide use (OR=1.8, 95% 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). [Note: an odds ratio of 1.0 would indicate no difference in odds of PD. An OR of 2.4 indicates the men who had used organochlorines were 140% more likely to develop Parkinson's on average.]
• 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 lend support to an association between PD and professional pesticide exposure and show that some pesticides (i.e., organochlorine insecticides) may be more particularly involved.
Source: Annals of Neurology, online Apr 13, 2009. DOI 10.1002/ana.21717, by Elbaz A, Clavel J, Rathouz PJ, Moisan F, Galanaud J, Delemotte B, Alperovitch A, Tzourio C. INSERM, Paris and Villejuif; UPMC University Paris, Paris and Villejuif; Mutualite Sociale Agricole, Bagnolet, France; Department of Health Studies, University of Chicago, Illinois, USA. [E-mail: firstname.lastname@example.org ]