Farming exposures and Alzheimer's disease: cross-sectional analysis within the French AGRICAN cohort

There is epidemiological evidence of an association between occupational pesticide exposure and cognitive impairment, but studies on the link with Alzheimer`s disease are scarce. We explored the association between agricultural exposures and Alzheimer`s disease in the AGRICAN cohort.

We analyzed the relationship between doctor-diagnosed Alzheimer`s disease and life-long exposures separately among men and women with the following exposures: work on a farm, pesticide use in any job, growing specific crops (N=13) or rearing animals (N=5), pesticide use on these crops/livestock, with adjustment for age, education, smoking, alcohol consumption and body mass index.

Among 109 287 participants in the analysis, 818 (267 men, 551 women) were classified as Alzheimer`s disease cases. Increased risks were seen for work on a farm [men: odds ratio (OR) 1.81, 95% confidence interval (CI) 0.92-3.57; women: OR 1.58, 95% CI 0.94-2.86] or pesticide use in any job (men: OR 1.14, 95% CI 0.85-1.53; women: OR 1.42, 95% CI 1.10-1.85). Risks for crops and livestock were close to unity when compared with non-farmers, except for pigs (OR 1.38, 95% CI 1.01-1.89) and rapeseed among men (OR 1.45, 95% CI 1.00-2.11) and sunflower among women (OR 1.55, 95% CI 0.90-2.66). Using pesticides increased the risk among men especially for sheep/goats (OR 1.98, 95% CI 1.18-3.34), pigs (OR 1.80, 95% CI 1.19-2.74), potatoes (OR 1.47, 95% CI 1.03-2.10) and meadows (OR 1.54, 95% CI 1.14-2.08). Among women, risks associated with pesticide use on crops were generally elevated, reaching a two-fold increase for corn, rapeseed, sunflower, field peas and fruit growing.

Our results suggest that agricultural exposures may play a role in Alzheimer's disease among both men and women, with the highest risks associated with pesticide use in certain livestock and crop activities.