Impact of ethnicity on multiple sclerosis progression: a Brazilian cohort
TL;DR
While univariate analysis indicated differences in disability scores between ethnoracial groups, ethnicity did not remain an independent predictor of MS progression after multivariate adjustment, Baseline EDSS was the only significant determinant of long-term functional evolution.
Abstract
Background: Multiple Sclerosis (MS) presents significant phenotypic variations among different ethnoracial groups, with literature reporting an often more severe clinical course and rapid progression to functional disability in populations of African descent. Given Brazil's high genetic admixture, it is imperative to characterize disease progression in this subpopulation. Objective: The objective of this study was to evaluate the impact of ethnicity on the progression of functional disability in a Brazilian cohort. Methods: A prospective cohort study, conducted from July 2023 to March 2026, evaluating patients diagnosed with MS (2017 McDonald criteria). Individuals with at least one year of follow-up, records of admission Expanded Disability Status Scale (EDSS) scores, and the ethnicity variable were included. The primary outcome analyzed was EDSS at the last follow-up. Univariate analysis using the Mann-Whitney U test and multivariate analysis using ordinal regression were performed to evaluate predictors of worse functional outcomes, controlling for age, sex, time to diagnosis, number of relapses, admission EDSS, and maintenance therapy at admission. Results: A total of 339 patients were included, with a median age of 43.6 years (IQR 34.4-51.6) and a female predominance (72.2%). The relapsing-remitting form was the most prevalent (87.6%). Regarding ethnicity, the sample comprised 28.3% White patients and 71.3% Black and Mixed-race patients. The median admission EDSS was higher in the Black and Mixed-race group (2.0; IQR 1.0-4.5) compared to White patients (1.5; IQR 0.0-3.5), as was the last evaluated EDSS (2.5 vs. 1.8, respectively). Univariate analysis indicated a statistical difference in the degree of disability between the groups (p = 0.017). However, in the multivariate ordinal regression, ethnicity was not sustained as an independent factor for functional progression (OR 1.24; 95% CI 0.77-2.02; p = 0.385). The only independent and highly significant predictor for disability was the admission EDSS (OR 2.88; 95% CI 2.48-3.36; p < 0.001). Remaining variables from the model did not reach statistical significance (p>0.05). Conclusion: While univariate analysis indicated differences in disability scores between ethnoracial groups, ethnicity did not remain an independent predictor of MS progression after multivariate adjustment. Baseline EDSS was the only significant determinant of long-term functional evolution.