Multiple sclerosis among first- and second-generation immigrant groups in Sweden

Objectives: Risk of multiple sclerosis (MS) is low among first-generation immigrants in Sweden. We aimed to study incident MS in first- and second-generation immigrant groups. Materials & Methods: We included adults aged 18 years and older in Sweden in first-generation (n = 6 042 891) and second-generation (n = 4 860 469) sub-studies. MS was defined via two diagnoses in the Swedish National Patient Register. MS risk was estimated by Cox regression, with hazard ratios (HRs) and 95% confidence intervals (CI), in different immigrant groups, using Swedish-born as referents in first-generation sub-study, and individuals with Swedish-born parents in the second-generation. Full models were adjusted for age, geographic residence in Sweden, educational level, marital status, neighborhood socioeconomic status, and co-morbidity. Results: MS was diagnosed among 10 746 individuals in the first-generation sub-study, (men 3055 and women 7691), and 11 737 in the second-generation sub-study (men 3549 and women 8188) in the period 1998-2015. The annual incidence rate was higher in Swedish-born compared to foreign-born, 11.5 vs 6.3 per 100 000 person-years (age-standardized to the European standard population). Fully adjusted HRs were lower in first-generation immigrant men (HR 0.72, 0.64-0.82) and women (HR 0.67, 0.62-0.73), and in second-generation immigrant men (HR 0.88, 0.79-0.97) and women (HR 0.79; 0.73-0.84). Among first-generation immigrants, lower HRs were found in most groups. Significance: The MS risk was lower in first- and second-generation immigrants compared to Swedish-born or individuals with Swedish-born parents.