Multiple Sclerosis and Occupational Exposures: A Case-Control Study

OBJECTIVE: To assess possible relationships between occupational exposures and risk of multiple sclerosis (MS). BACKGROUND: MS is recognized as a multi-factorial disease, in which genetic and environmental factors could act together. The exposure to substances spreading in work environment and potentially neurotoxic could be one of the co-factors involved in MS etiology, but there are very few studies about the association between occupational status and MS. DESIGN/METHODS: We carried out a case-control study, where cases were patients included in the MS Register of the Province of Pavia, Northern Italy, and controls, 1:2 matched by sex and age, were randomly selected from the National Health Service population files. The occupational histories were obtained from the Italian Institute for Social Providence (INPS) archives by automatic linkage using Italian Occupational Cancer Monitoring (OCCAM) method, that estimate the risk of specific occupational diseases, by geographic area and industrial sector. RESULTS: We included 660 MS patients (411 F, 249 M; mean age 49.1 years; mean disease duration 16.7 years) and 1320 controls. The risk of MS turned out to be higher in workers of mechanic industry (OR 17.4, 90% CI 5-60.6, p < 0.001), leather industry (OR 11.5, 90% CI 4.9-26.9, p < 0.001), and agriculture (OR 19.1, 90% CI 4.2-87.6, p < 0.001). CONCLUSIONS: The case-control study design with OCCAM approach appears to be a useful and low-cost method, not only for occupational cancer surveillance, but also for the study of diseases, like MS, whose etiology is not well defined yet. Our findings indicate that solvent exposures could be related to the risk of MS, as both shoe/leather workers and mechanic industry workers are exposed to organic solvents. A major risk of MS was also found among workers engaged in agriculture, suggesting a role of pesticides, whose neurotoxic effect is well known.