Common Social and Health Disparities Contribute to Racial Differences in Ambulatory Impairment in Multiple Sclerosis

Abstract

BACKGROUND: We previously reported more rapid accrual of ambulatory impairments in Black compared to White individuals with relapsing remitting multiple sclerosis (RRMS) and higher body mass index (BMI). Hypertension and lower neighborhood socioeconomic status (SES) were associated with greater impairment, irrespective of race. We hypothesize that these common social and health inequities may explain a substantial portion of the racial differences in ambulation in American individuals with RRMS. METHODS: Causal mediation analyses investigated baseline and change-over-time mediators of ambulatory impairment differences between 1795 Black and White individuals with RRMS using a retrospective cohort study comprised of electronic health record data from 8491 clinical encounters between 2008 and 2015 where Timed 25-Foot Walk (T25FW) speeds without assistive devices were recorded. The hypothesis was that BMI, neighborhood SES, and hypertension were possible mediators. RESULTS: At baseline, Black individuals with RRMS (n = 175) had significantly slower T25FW speeds (5.78 vs 5.27 ft/s), higher BMI, a higher prevalence of hypertension, and they were more likely to live in lower-income neighborhoods than White individuals (n = 1,620). At baseline, a significant proportion (33.7%; 95% CI, 18.9%-59.4%) of the T25FW difference between Black and White individuals was indirectly due to a higher BMI (12.5%), hypertension burden (9.5%), and living in lower-income neighborhoods (11.2%). Once baseline mediation relationships were accounted for, there were no significant longitudinal mediation relationships. CONCLUSIONS: The findings implicate social and health disparities as prominent drivers of ambulatory differences between Black and White individuals with RRMS, suggesting that wellness and health promotion are essential components of MS care, particularly for Black individuals.