“It has previously been thought that [multiple sclerosis (MS)] is less common among non-European Caucasian White populations, driven partly by the well-known association of incidence with latitude,” said Christopher Orlando, MD, during a presentation at AAN 2022, before adding, “It is abundantly clear at this point that this idea is not true.”
Using Neighborhood-Level Data
Data indicate that, when compared with White patients with MS, Black and Hispanic patients experience greater disability despite similar rates of progression and adequate treatment. “Black patients in particular appear to have a higher incidence of disease and a greater proportion of progressive disease phenotypes,” added Dr. Orlando. “While much remains to be discovered of the genetic underpinnings of MS, what we do know does not support the idea that minorities would have a predilection to more severe disease. For example, the well-known high-risk allele HLA DRB1*1501 appears to have a lower frequency in African populations, compared with European [populations].” With prior research that corrected for social determinants of health showing a reduced association between race and MS disability, but not completely explaining it, the study team sought to determine if relative socioeconomic deprivation may predict racial and ethnic disparities in MS disability.
In a first-of-its-kind study, the researchers applied neighborhood-level data combined with socioeconomic status and social deprivation data to the study of racial and ethnic disparities in patients with MS. They reviewed the electronic medical records of 300 age- and sex-matched White, Black, and Hispanic patients, abstracted data reflecting clinical characteristics, calculated baseline and follow-up Expanded Disability Status Scale (EDSS) scores and modeled them using linear regression, matched geocoded home addresses with census tract-level CDC Social Vulnerability Index (SVI) scores, and compared groups using Kruskall-Wallis H, ANOVA, and chi-square tests.
Stark Differences With Social Determinants of Health
Dr. Orlando and colleagues found that both baseline and follow-up EDSS scores were higher in Hispanic and Black patients than in White patients (P<0.001). They observed no significant differences with potential confounders, which included diagnostic lag, age at onset, and follow-up length. However, they did find significant differences in overall SVI (P=0.0001) and sub-scores (socioeconomic, household composition, minority/language, housing/transportation), with White patients residing in the least vulnerable neighborhoods and Black patients residing in the most vulnerable. Indeed, while SVI was not significant in the initial model used (P=0.151), it was deemed significant in a model that excluded race/ethnicity variables (P=0.032).
“More stark differences appeared when we compared social determinants of health,” noted Dr. Orlando. “Hispanic patients were less likely to speak English as a primary language or to complete 12 years of education. Black patients were less likely to live in a rural county and more likely to be unemployed. One particularly stark difference was in the number of unemployed specifically due to their MS, with only 1 White patient [1.1%], 7 Hispanic patients [7.8%] and 27 Black patients [31.0%].” In multivariate regression models, diagnostic lag, progressive disease phenotype, Hispanic ethnicity, Black race, and private insurance were significant.
A Caution From Dr. Orlando
“It would appear that the sheer complexity both in variety and magnitude of the social determinants of health are such that by far the stronger association is with race and ethnicity, which are surrogates for any number of social determinants and societal inequities,” Dr. Orlando explained, before cautioning that these study results do not indicate a biologically intrinsic factor. “I want to warn against that kind of thinking in the strongest possible terms,” he added. “It is implausible on several levels. It’s not biologically plausible based on our understanding that race and ethnicity are not genetic constructs. And it’s also not numerically plausible based on these data.”
With many drivers of the inequities uncovered in this and other studies not fully explained, Dr. Orlando added that “as long as this is the case, our ability to fulfill our roles as physicians will be limited in several important ways. Our ability to assess our patients’ individual risk will be missing key information, which will limit the efficacy of shared decision-making, which of course is the cornerstone of MS treatment. In addition, we will continue to struggle to include minority patients in our research studies, and the very design and results of those studies may be misguided, as we will either fail to include these populations, or we will fail to adjust for important confounders.”
