What leads to racial differences in MS progression and severity?


Over the last several years, multiple sclerosis researchers have further delved into the idea that race and ethnicity can play a role in disease severity and how MS progresses through the body. Though these investigations raise new questions as often as they provide concrete answers; they also reinforce the need to understand why MS affects races differently and the underlying health disparities that may contribute to those differences.

A narrative review recently published in JAMA Neurology sought to show how social determinants of health impact health outcomes in Black, Hispanic, and Latinx patients with MS and related disorders. To begin their analysis of articles published between Jan. 1, 2014, to March 1, 2021, the researchers – led by Lilyana Amezcua, MD, of the University of Southern California, Los Angeles – acknowledged the once-held belief that Black people have a lower risk of developing MS and then cited a 2013 population-based study, published in Neurology, that estimated MS to be more prevalent among Black Americans than White Americans.

The authors also referenced several studies that indicate “greater disease severity and more rapid disease progression” in Black, Hispanic, and Latinx patients with MS, compared with White patients, as measured by mean Patient-Derived Multiple Sclerosis Severity Score. One of the relevant limitations they highlighted – referral center bias, “owing to Black patients with MS seeking care at a later stage, compared with White patients” – may itself be an indicator of inequity.

Dr. Lilyana Amezcua
Image credit: Doug Brunk/MDedge News
Top image credit: kali9/E+/Getty Images

Other findings include Black patients with MS being less likely than White patients to use case management (odds ratio, 0.36; 95% confidence interval, 0.21-0.62); equipment, technology, and modification (OR, 0.69; 95% CI, 0.49-0.97); or nursing services (OR, 0.52; 95% CI, 0.28-0.98). Black, Hispanic, and Latinx patients with neurologic illnesses are also less likely to seek outpatient care (OR, 0.72; 95% CI, 0.64-0.81) and more likely to seek care in an ED (OR, 0.61; 95% CI, 0.54-0.69).

“The differential utilization pattern of services found between Black individuals and White individuals and Black individuals’ greater utilization of the ED over specialty care could lead to underutilization of magnetic resonance imaging and therefore delay in diagnosis,” the authors wrote.

A coauthor on the JAMA Neurology study – Victor Rivera, MD, of the Baylor College of Medicine, Houston – previously presented a study at the 2021 annual meeting of the American Academy of Neurology that found Blacks and Hispanics with MS experienced more severe disease and were less likely than White patients to start on disease-modifying therapies (DMTs).

Though 73% of their 695 patients had mild MS, 21% of the Black/African American patients had substantial MS-related disability, compared with 10% of the White patients. In turn, 64% of the White patients were treated with DMTs, compared with 39% of the Black non-Hispanic patients and 26% of the Black Hispanic patients.

“It’s very complex,” Dr. Rivera responded when asked why DMTs were not being used in certain populations. “I think it’s a combination of factors, because there’s no question that socioeconomic and cultural factors play a very important role in access to therapies in these particular groups.”

Dr. Victor Rivera

Systemic disparities may contribute to MS severity

Another recent cross-sectional study, published in Neurology, examined possible associations between disease severity, race, and socioeconomic status in Americans with MS. Of the study’s 7,530 White Americans and 1,214 Black Americans – who were as a group younger, had lower levels of education, and were less likely to be employed than their counterparts – the Black patients had worse odds of severe disability (OR, 1.47; 95% CI, 1.18-1.86), an average of approximately five fewer correct responses during cognitive processing speed tests (95% CI, –5.72 to –4.41), more brain MRI lesions, and lower overall and gray-matter brain volumes.

“Across the board, [Black American] patients with MS appear to have greater burden of inflammatory and neurodegenerative measures of MS, along with worse neurological performance,” lead author Karla Gray-Roncal, MD, of Johns Hopkins University, Baltimore, and coauthors wrote.

After multivariate analysis, the study found that lower median household income was associated with slower cognitive processing and walking speeds in the White patients. Lower area deprivation index (ADI) scores were also associated with slower processing and manual dexterity speeds. In Black patients, lower household income was only associated with slower manual dexterity; lower ADI scores were not meaningfully associated with negative outcomes.

“It is likely that there may still be unmeasured confounders related to systematic racism and health outcomes that explain the findings herein,” the authors wrote, with Lana Zhovtis Ryerson, MD, of New York University Langone Health adding in an accompanying press release that “future studies should consider the role of unmeasured factors like systemic racism to see if they may play a role in greater disability among Black people with MS.”

Additional research from earlier in 2021 found that race may be a relevant factor when assessing responses to a common MS treatment. In a single-center study of 168 participants with either MS or neuromyelitis optica spectrum disorder who underwent anti-CD20 infusion therapy – 36% of which identified as White and 36% of which identified as Black – it was discovered that B cells repopulated more quickly in Black patients.

Dr. Lana Zhovtis Ryerson

Dr. Ilya Kister

Dr. Gregg J. Silverman

“Our findings raise the question of whether the same therapy dose may be equally effective for all people,” said coauthor Ilya Kister, MD, of NYU Langone Health.

The researchers emphasized that more studies are needed to determine the reason behind the differing responses, noting that body mass index has been previously identified as a characteristic to consider when possibly modifying dosing frequency.

“As we say in science: It gives us an answer but it raises even more questions,” added coauthor Gregg J. Silverman, MD, of NYU Langone Health, “which may well be important for helping us understand how the agent works and how the disease affects different people.”