Healthcare is a reflection of how a society cares for its most vulnerable individuals. It is a well-known fact that the U.S. spends more money on healthcare than any other country. Yet among wealthy nations, they have the lowest life expectancy. This illustrates the fact that delivery of medical care is only a minor element in the well-being of a society. Services like maternity leave, housing, education, cancer screening programs, good food, drug-abuse or mental-health counseling are what matters in the – preferable sweet – end. Also in MS, mere access to specialist care and disease-modifying treatments is only one side of care medal. Especially, if you are a Black American (BA).
In seven U.S. MS centres, researchers assessed whether 1,214 BA people with MS (pwMS) did differently in terms disease outcomes compared to 7,530 White Americans (WA). To correct for socio-economic status, they included employment, education level and insurance status as covariates in the analysis. Even when taking these factors into account, BA pwMS did worse on almost all neuroperformance outcomes compared to WA with similar disease characteristics. BA had a 50 % higher odds of severe versus moderate MS, and they performed less well in terms of dexterity, walking speed and cognition. Most worrisome were the MRI data. BA pwMS have consistently lower levels of cortical grey matter. The latter is meaningful as grey matter volume is one of the most important factors involved in faster disease progression.
The biggest trap when interpreting the results presented in this article is ‘reverse causation’. This term refers to the the situation in which the outcome (= being BA) precedes and causes the exposure (= worse MS disease) instead of the other way around. Let me give you a more ‘local’ example that will clarify the concept. Fampridine is a drug that improves walking speed in about 35% of pwMS. Imagine we would assess the association between walking speed in the South of Enland (e.g. less than half of the NHS commissioning groups provide fampridine) vs. the North of England (e.g. more than half provide fampridine). The results would show an association between geographical location and walking speed. Do people in the Southern England have a biologically different disease which has a more pronounced effect on lower limb function? No. They just have less access to fampridine.
The assumption that insurance status (which is a maze of thorns in the U.S.), education level (measured by years of eduction raising quality vs. quantity issues) and employment status would accurately reflect socio-economic differences between BA and WA is optimistic. To date, we know that BA pwMS do worse in terms of neurological outcomes without having a plausible biological explanation. Obviously, the problem is that skin colour is a tag for genetic, environmental, cultural and socio-economic differences. Many remain unaddressed in this study, and are inherently difficult to measure – even when using longitudinal study designs. BA with neurologic conditions are less likely to see an outpatient neurologist, are more likely to be cared for in emergency departments, and are less likely to have access to specialist MS care. This translates into less knowledge of the disease, less recognition of MS symptoms and less initiation/adherence to treatment. It is indeed true that BA pwMS have a different genetic background in which the frequency of some important immunological MS risk genes such as the HLA gene differ. Although genetic factors may play a role when it comes to explaining differences of disease presentation/severity, they do not account for the majority of MS risk.
Overall, this article highlights the need to investigate how MS outcomes are modified by comorbid conditions, environmental and social determinants of health: inclusive research. The recent data on COVID-19 outcomes in BAME groups in the UK suggest this problem extends way beyond MS, neurology and the U.S. For now (and tomorrow), it would be already a big step forward if we as physicians start openly acknowledging the specific morbidity/mortality risks and barriers facing non-White people with MS.
Disclaimer: Please note that the opinions expressed here are those of dr. Ide Smets and do not necessarily reflect the position of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust.
Association of Disease Severity and Socioeconomic Status in Black and White Americans With Multiple Sclerosis
Karla Gray-Roncal 1, Kathryn Fitzgerald 2, Lana Zhovtis Ryerson 3, Leigh Charvet 3, Sandra D Cassard 2, Robert Naismith 4, Daniel Ontaneda 5, Kedar Mahajan 5, Wanda Castro-Borrero 6, Ellen Mowry 2
- PMID: 34193590
- DOI: 10.1212/WNL.0000000000012362
Objective: To compare clinical and imaging features of multiple sclerosis (MS) severity between Black Americans (BA) and White Americans (WA) and evaluate the role of socioeconomic status. Methods: We compared BA and WA participants in the Multiple Sclerosis Partners Advancing Technology Health Solutions (MS PATHS) cohort with respect to MS characteristics including self-reported disability, objective neurologic function assessments, and quantitative brain MRI measurements, after covariate adjustment (including education level, employment, or insurance as socioeconomic indicators). In a subgroup, we evaluated within-race, neighborhood-level indicators of socioeconomic status (SES) using 9-digit ZIP codes. Results: Of 1,214 BAs and 7,530 WAs with MS, BAs were younger, had lower education level, and were more likely to have Medicaid insurance or be disabled or unemployed than WAs. BAs had worse self-reported disability (1.47-fold greater odds of severe vs. mild disability, 95% CI 1.18, 1.86) and worse performances on tests of cognitive processing speed (-5.06 fewer correct, CI -5.72, -4.41), walking (0.66 seconds slower, 95% CI 0.36, 0.96) and manual dexterity (2.11 seconds slower, 95% CI 1.69, 2.54). BAs had more brain MRI lesions and lower overall and gray matter brain volumes, including reduced thalamic (-0.77 mL, 95% CI -0.91, -0.64), cortical (-30.63 mL, 95% CI -35.93, -25.33), and deep (-1.58 mL, 95% CI -1.92, -1.23) gray matter volumes. While lower SES correlated with worse neuroperformance scores in WAs, this association was less clear in BA. Conclusion: We observed a greater burden of disease in BAs with MS relative to WAs with MS, despite adjustment for SES indicators. Beyond SES, future longitudinal studies should also consider roles of other societal constructs (e.g., systemic racism). Such studies will be important for identifying prognostic factors and optimal treatment strategies among BAs with MS is warranted.