Environmental pesticide exposure as a risk factor for Alzheimer's disease: a case-control study.

The aim of this study was to evaluate the influence of pesticide exposure on the development of Alzheimer's disease (AD), taking into account the potentially confounding factors (genetic, occupational exposure, and sociodemographic). The 1924 study participants (>70 years old) were randomly selected in the Saguenay-Lac Saint-Jean region (Quebec, Canada). The AD diagnosis was established in three steps according to recognized criteria. Sixty-eight cases were paired with a nondemented control for age (+/-2 years) and sex. Structured questionnaires addressed to subjects and proxy respondents allowed a description of the sociodemographic characteristics, lifestyle characteristics, and residential, occupational, familial, and medical histories. Assessment of environmental exposure to pesticides was based on residential histories and the agriculture census histories of Statistics Canada (1971-1991) for herbicide and insecticide spraying in the area. Statistical analyses were performed with a logistic regression, adjusting for potential confounding factors. The results failed to show a significant risk of AD with an exposure to herbicides, insecticides, and pesticides. However, future investigations are needed to establish more precisely the identification, measurement, mobility, and bioavailability of neurotoxic pesticide residues in relation to AD.