Environmental factors in multiple sclerosis, focusing exposure to organic solvents

Abstract

Results obtained in previous studies on the relationship between exposure to organic solvents and risk of multiple sclerosis are not entirely consistent. The aim of this study was to investigate the relationship between exposure to organic solvents and risk of multiple sclerosis and possible interactions between exposure to solvents and smoking; exposure to solvents and infectious mononucleosis; exposure to solvents and D-vitamin. The case-control study on Evironmental Factors In Multiple Sclerosis (EnvIMS) was used. We examined two samples, the first one made up of 1.197 MS patients, and the second one, 2.361 healthy controls from Sweden and Norway; both group were matching in terms of their sex and age. We examined their exposure to organic solvents prior to the study; we also examined whether they had suffered from infectious mononucleosis, their outdoor activity (D-vitamin) and smoking status. The relationships between exposure to solvents and other risk factors were estimated as odds ratios (ORs) with 95 % confidence interval (95 % CI) using logistic regression. Exposure to organic solvents was found to be associated with an increased MS risk, OR 1.51 (95 % confidence interval (CI): 1.19–1.90; p = 0.001), adjusted OR was 1.36 (95 % CI: 1.05–1.75; p = 0.020). Adjusted ORs for different combinations including exposure to solvents and other risk factors such as smoking, infectious mononucleosis and D-vitamin showed an increased risk of MS. Among those who reported infectious mononucleosis there was no increased risk associated with exposure to solvents, OR 1.03 (95 % CI: 0.48–2.19). The increased risk seems to be present only in individuals with unfavorable smoking status and low D-vitamin status.

Keywords

• multiple sclerosis
• risk factors
• organic solvent
• smoking
• infectious mononucleosis
• d-vitamin