Work-related exposure to organic solvents and the risk for multiple sclerosis—a systematic review

PURPOSE: Multiple sclerosis (MS) is a chronic progressive neurological disorder. Several environmental factors have been discussed as possible causing agents, e.g. organic solvents, whose impact on the disease is analysed in this review. METHODS: Systematic search strategies were used to identify high-quality studies of workers exposed to organic solvents, published up to September 30, 2019, in databases, such as PubMed, Cochrane library and Scopus. The exposure was in most studies obtained by questionnaires, supplemented with telephone interviews. The diagnosis MS was mainly detemined following a thorough neurological examination. Finally, fourteen case–control studies and two cohort studies met the inclusion criteria and were included in the meta-analysis. Random effects models were used to pool the results of the studies. RESULTS: The odds ratios from the 14 case–control studies included in the meta-analysis ranged from 0.12–4.0. Five case–control studies and one cohort study showed a significant association between the development of multiple sclerosis and exposure to organic solvents. The results from the other nine case–control studies and from one of the two cohort studies did not reach statistical significance. The pooled data from the 14 case–control studies gave an OR of 1.44 (95% CI 1.03–1.99), which shows a moderately increased risk of developing MS after exposure to organic solvents. CONCLUSIONS: The final interpretation of the result is that organic solvents may be slightly associated with an increased risk to develop MS. In addition, other factors, e.g. genetic markers and smoking, may contribute to the development of the disease.