(HealthDay News) – Exposure to pesticides or solvents is associated with an increased risk of Parkinson’s disease, according to a meta-analysis published in the May 28 issue of Neurology.

To examine the risk of Parkinson’s disease associated with exposure to pesticides and solvents, Gianni Pezzoli, MD, from the Istituti Clinici di Perfezionamento in Milan, and Emanuele Cereda, MD, PhD, from Fondazione IRCCS Policlinico San Matteo in Pavia – both in Italy, conducted a meta-analysis of data from 104 prospective cohort and case-control studies. All studies provided risk and precision estimates that linked Parkinson’s disease to pesticide or solvent exposure or to proxies of exposure.

The researchers found that study quality was not a source of heterogeneity in prospective studies. Parkinson’s disease was associated with farming, and there was a highly significant correlation with pesticides in studies with self-reported Parkinson’s disease diagnosis. In risk estimates for some exposures, study quality seemed to be a source of heterogeneity in case-control studies, with a reduction in heterogeneity frequently seen with higher study quality. In high-quality case-control studies, exposure to any-type pesticides, herbicides, and solvents correlated with increased Parkinson’s disease risk. Specifically, there was about a two-fold increase in risk with exposure to paraquat or maneb/mancozeb. Based on high-quality studies with >200 cases, heterogeneity was above 40% only for insecticides, organochlorines, organophosphates, and farming. There was also a significant risk associated with rural living.

“The literature supports the hypothesis that exposure to pesticides or solvents is a risk factor for Parkinson’s disease,” the authors write.

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