Interactions Between Organic Solvent Exposure, Smoking, and MS Susceptibility

Exposure to organic solvents increases the risk of developing multiple sclerosis (MS) in individuals with a genetic susceptibility, especially if the individual is also exposed to smoking, according to a study published in Neurology.

This case-control population-based study used data from the Epidemiological Investigation of Multiple Sclerosis to assess the influence of organic solvent exposure on MS risk, as well as the interaction between organic solvent exposure, genetic susceptibility (as measured by human leukocyte antigen [HLA] alleles), and smoking habits. The study assessed 2042 patients with MS and 2947 controls matched by residential area, sex, and age.

Using logistic regression, investigators found a significant association between organic solvent exposure and elevated risk of developing MS (adjusted odds ratio [OR] 1.5; 95% CI, 1.2-1.8; P=.0004), with trends of increasing risk found with total hours of exposure (P=.001) and increasing duration of organic solvent exposure (P=.04). Study participants who carried the HLA-DRB1 15 allele (increasing MS risk), lacked the HLA-A 02 allele (protective against MS), and were exposed to both organic solvents and smoking showed a 30-fold increased risk for MS compared with participants without exposure or genetic risk factors for MS (OR 30.3; 95% CI, 11.7-78.3). This interaction was observed between these risk factors for smokers (total attributable proportion due to interaction [TotAP] 0.7, 95% CI, 0.4-1.0) and for participants who never smoked (TotAP 0.4; 95% CI, 0.07-0.7).

Study investigators conclude, “[we] demonstrate a significant interaction between the MS risk HLA genes and exposure to organic solvents regarding MS risk, similar to the previously reported gene-environment interaction involving the same MS risk HLA genes and smoke exposure. We hypothesize that different sources of lung irritation may contribute to induce an immune reaction against modified self-proteins induced by lung irritation or against potentially autoaggressive cells resident in the lungs, and promote MS development in people with a genetic susceptibility to the disease.”

Reference

Hedström AK, Hössjer O, Katsoulis M, Kockum I, Olsson T, Alfredsson L. Organic solvents and MS susceptibility: Interaction with MS risk HLA genes [published online July 3, 2018]. Neurology. doi: 10.1212/WNL.0000000000005906