Exposure to pesticides and risk of amyotrophic lateral sclerosis: a population-based case-control study

Backgroud: A few epidemiologic studies suggested an association of agricultural work and pesticides exposure with a severe degenerative disease of the motor neurons, amyotrophic lateral sclerosis (ALS), though conflicting results have also been provided. Some laboratory investigations have also provided biological plausibility for this hypothesis, indicating that pesticides might adversely affect the motor neurons.Objective: We investigated through a population-based case-control study the possible relation between pesticides and ALS in the northern Italy municipality of Reggio Emilia. Methods: By administering a questionnaire, we investigated occupational history and leisure time habits of the 41 ALS patients diagnosed in the 1995-2006 period, and of 82 age- and sex-matched randomly sampled population controls, to ascertain the regular use of pesticides. All cases of ALS appeared to be of the sporadic form of the disease and were classified as ‘certain’ or ‘probable’ forms of the disease, according to the so-called ‘El Escorial criteria’.Results: More cases than controls were found to have been exposed to pesticides for at least six months (31.7% versus 13.4%, respectively), in all cases within the occupational environment. In a conditional logistic regression model, we found an excess ALS risk associated with exposure to pesticides, with an odds ratio of 3.6 and a 95% confidence interval of 1.2-10.5. Inclusion in the statistical analysis of potential confounders, such as electromagnetic fields exposure and drinking water chemical composition, did not modify such association and it even enhanced it.