Ascherio A et al. (2006) Pesticide exposure and risk for Parkinson's disease. Ann Neurol [doi: 10.1002/ana.20904]

Evidence suggests that exposure to pesticides might be a risk factor for the development of Parkinson's disease (PD). When administered at high doses, certain pesticide compounds can cause degeneration of dopaminergic cells in the substantia nigra. Ascherio et al. tested the association between pesticide exposure and PD in a prospective investigation. The study population comprised 143,325 participants from the Cancer Prevention Study II Nutrition Cohort who did not have a diagnosis or symptoms of PD on enrollment in 1992.

Analyses adjusted for age, sex and smoking status showed that the 5.7% of participants who reported exposure to pesticides before 1982 had a 70% higher incidence of PD 10–20 years after pesticide exposure than those who had not been exposed. The mean age of PD onset was unaffected by pesticide exposure, being approximately 70 years in both exposed and unexposed participants. The exposed population had a slightly lower educational level than the nonexposed population, but other aspects of lifestyle were similar. Data were insufficient to determine how duration of exposure might affect the risk of PD. No significant association was found between incidence of PD and exposure to any of the other environmental pollutants examined.

On the basis of these results, the authors conclude that pesticide exposure does increase the risk of PD. They suggest that future studies should seek to identify the specific compounds associated with this risk.