Premorbid Sociodemographic Status and Multiple Sclerosis Outcomes in a Universal Health Care Context

IMPORTANCE: Multiple sclerosis (MS) severity may be informed by premorbid sociodemographic factors. OBJECTIVE: To determine whether premorbid education, income, and marital status are associated with future MS disability and symptom severity, independent of treatment, in a universal health care context. DESIGN, SETTING, AND PARTICIPANTS: This nationwide observational cohort study examined data from the Swedish MS Registry linked to national population registries from 2000 to 2020. Participants included people with MS onset from 2005 to 2015 and of working age (aged 23 to 59 years) 1 year and 5 years preceding disease onset. EXPOSURES: Income quartile, educational attainment, and marital status measured at 1 and 5 years preceding disease onset. MAIN OUTCOME AND MEASURES: Repeated measures of Expanded Disability Status Scale (EDSS) scores and patient-reported Multiple Sclerosis Impact Scale (MSIS-29) scores. Models were adjusted for age, sex, relapses, disease duration, and treatment exposure. Secondary analyses further adjusted for comorbidity. All analyses were stratified by disease course (relapse onset and progressive onset). RESULTS: There were 4557 patients (mean [SD] age, 37.5 [9.3] years; 3136 [68.8%] female, 4195 [92.1%] relapse-onset MS) with sociodemographic data from 1-year preonset of MS. In relapse-onset MS, higher premorbid income and education correlated with lower disability (EDSS, −0.16 [95% CI, −0.12 to −0.20] points) per income quartile; EDSS, −0.47 [95% CI, −0.59 to −0.35] points if tertiary educated), physical symptoms (MSIS-29 physical subscore, −14% [95% CI, −11% to −18%] per income quartile; MSIS-29 physical subscore, −43% [95% CI, −35% to −50%] if tertiary educated), and psychological symptoms (MSIS-29 psychological subscore, −12% [95% CI, −9% to −16%] per income quartile; MSIS-29 psychological subscore, −25% [95% CI, −17% to −33%] if tertiary educated). Marital separation was associated with adverse outcomes (EDSS, 0.34 [95% CI, 0.18 to 0.51]; MSIS-29 physical subscore, 35% [95% CI, 12% to 62%]; MSIS-29 psychological subscore, 25% [95% CI, 8% to 46%]). In progressive-onset MS, higher income correlated with lower EDSS (−0.30 [95% CI, −0.48 to −0.11] points per income quartile) whereas education correlated with lower physical (−34% [95% CI, −53% to −7%]) and psychological symptoms (−33% [95% CI, −54% to −1%]). Estimates for 5-years preonset were comparable with 1-year preonset, as were the comorbidity-adjusted findings. CONCLUSIONS AND RELEVANCE: In this cohort study of working-age adults with MS, premorbid income, education, and marital status correlated with disability and symptom severity in relapse-onset and progressive-onset MS, independent of treatment. These findings suggest that socioeconomic status may reflect both structural and individual determinants of health in MS.