While the causes of Parkinson's disease are not fully known, many studies have suggested that factors other than inherited genes play a large role. Data suggests that chronic exposure to pesticides, even in low doses, could be a risk factor. To examine this association, researchers led by Alberto Ascherio, M.D., Dr.PH of the Harvard School of Public Health conducted a prospective study of Parkinson's disease among a large cohort of Americans.
They included male and female participants of the Cancer Prevention Study II Nutrition Cohort who, beginning in 1982, completed extensive lifestyle questionnaires that included questions about occupation and exposure to pesticides and other potentially harmful materials. The researchers focused their study on 143,325 individuals who completed a follow-up survey in 2001, responded to a question about lifetime occurrence of Parkinson's disease, and had no symptoms at baseline.
The researchers requested the medical records of all study participants who reported a new diagnosis of Parkinson's disease after 1992 that is 10 or more years after the reported exposure to pesticides -- to independently confirm the diagnosis. 413 cases were included in this study, and statistical analyses were performed to determine the association between pesticide exposure and Parkinson's disease.