Does low socioeconomic status in early life protect against multiple sclerosis? A multinational, case-control study

Background and purpose: The findings from existing research on the association between socioeconomic status (SES) and multiple sclerosis (MS) are inconsistent. Most previous studies are limited to one country and do not adequately adjust for other risk factors for the disease. Methods: The association between SES and MS was examined using data from the multinational Environmental Risk Factors in Multiple Sclerosis (EnvIMS) case-control study, comprising 2144 cases and 3859 controls from Norway, Canada and Italy. Multiple logistic regression was used to estimate the odds ratios and 95% confidence intervals for the association between early life SES, measured by parental educational level, and MS. Analyses were adjusted for age, sex, sunlight exposure, history of infectious mononucleosis, smoking, obesity and family size. Results: Relative to those whose parents had primary school education or below, the adjusted odds ratio (95% confidence interval) for MS amongst individuals with university-educated parents, and the P value for trend across education levels, were 1.45 (1.03-2.05) in Canada (P for trend 0.030), 1.09 (0.85-1.39) in Norway (P for trend 0.395) and 0.65 (0.39-1.07) in Italy (P for trend 0.158). Conclusion: There is no consistent association between parental SES and MS risk in Norway, Canada and Italy, with a protective effect of low SES only found in Canada