Living near waterbodies as a proxy of cyanobacteria exposure and risk of amyotrophic lateral sclerosis: a population based case-control study

Background: Epidemiological studies highlighted the possibility that exposure to cyanotoxins leads to the development of the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Methods: We devised a population-based case-control study in two Italian populations. We used residential proximity of the residence to water bodies as a measure of possible exposure to cyanotoxins. Results: Based on 703 newly-diagnosed ALS cases and 2737 controls, we calculated an ALS odds ratio (OR) of 1.41 (95% CI: 0.72-2.74) for current residence in the vicinity of water bodies, and a slightly lower estimate for historical residence (OR: 1.31; 95% CI: 0.57-2.99). Younger subjects had a slighter higher OR compared with subjects > 65 years (OR: 1.56; 95% CI: 0.59-4.17). The Northern Italy province of Modena showed the highest OR, especially when historical residence was considered. Conclusions: Though we used an indirect index of exposure, susceptible to misclassification, our results offer some support for the hypothesis that cyanotoxin exposure increases ALS risk.