Environmental and occupational risk factors of amyotrophic lateral sclerosis: a population-based case control study

Background and aims Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of the motor neuron. Its etiology is still largely unknown, except for some rare forms of genetic origin, but environmental factors may have an important role. Methods We performed a population case-control study in three Italian provinces (Modena, Reggio Emilia and Catania) in order to assess the possible etiologic role of some environmental factors. We administered 877 questionnaires by mail or by person in a neurological office to collect information about personal, clinical and professional history to ALS cases newly diagnosed in the 2008-2011 period and age- and sex-matched population controls. Results Analysis of the returned questionnaires (18,5%, 61 cases and 101 controls) showed an increased risk when examining clinical information for reported trauma (OR 1.20, 95%CI 0.63-2.30), head (OR 3.04, 1.23-7.55) and chest trauma (OR 2.65, 95%CI 0.72-9.78). History of previous fractures has an OR of 1.10 (95%CI 0.58-2.11), but for head fracture OR raised to 5.17 (95%CI 0.53-50.88). With reference to occupational history an excess of risk was found for employment in agriculture (OR 2.44, 95%CI 1.03-5.79) and for welding (OR 1.25, 95%CI 0.27-5.80). Occupational exposure to lead (OR 1.27, 95%CI 0.74-2.17), thinners (OR 1.12, 95%CI 0.66-1.91) and solvents (toluene/xylene) (OR 1.24, 95%CI 0.72-2.13) provide some excess risk. Considering 'extra-working' activities, we found an excess disease risk for hunting (OR 1.69, 95%CI 0.33-8.65), painting (OR 1.46, 95%CI 0.47-4.58), modelling with glue (OR 1.72, 95%CI 0.57-5.17), gardening (OR 1.15, 95%CI 0.64-2.08), football (OR 1.04, 95%CI 0.44-2.47) and pesticides (OR 1.98, 95%CI 0.76-5.12) and herbicides use (OR 2.27, 95%CI 0.72-7.19). Conclusions Thoughthese results must be assessed with caution for the risk of selection and information bias, they suggest potential etiologic clues to ALS etiology which are worthy of further study.