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Multiple sclerosis (MS) occurs at the same rate in Black populations as it does in white populations, a large retrospective cohort study found.

In Southern California, age- and sex-standardized prevalence of MS per 100,000 population was similarly high among Black and white persons (226 and 238 per 100,000, respectively) and significantly lower among Hispanic and Asian persons (70 and 23 per 100,000, respectively), researchers reported online in .

"MS has long been believed to be a disease of white people, but the prevalence of MS in Black people has been understudied and therefore underrecognized," said study author Annette Langer-Gould, MD, PhD, of Kaiser Permanente Southern California in Los Angeles in a statement. "The findings of our study and other recent indicate that MS has affected Black and white adults at similar rates for decades."

In an , Roy Hamilton, MD, of the University of Pennsylvania in Philadelphia, and Olga Ciccarelli, MD, of University College London Queen Square Institute of Neurology, echoed the observation that "prior misconceptions about racial disparities in MS may have arisen, in part, from systematic biases in the employed to address the issue...[such as] data obtained in the 1950s, [when it was] significantly harder for Black veterans to become service connected and included in such investigations."

"The notion that Black persons are inherently to diseases goes beyond neurological diseases and MS, and has a long, enduring, and pernicious history," they wrote.

That "a substantial proportion of medical trainees and professionals continue [to] believe [these] medical myths," Hamilton and Ciccarelli chalked up to "a systemic failure to look for or treat that disorder in those marginalized populations, with tragic consequences."

Pointing out that calculation of disease prevalence is based on both incidence and longevity, and that Black persons in the US have a relatively shorter life expectancy than white individuals, Langer-Gould and coauthors called their findings of a similar MS prevalence among older Black and white persons "rather remarkable" and confirmation that "MS is not a new disease among US Black individuals."

Of more than 2.6 million adults from the multi-ethnic, community-dwelling members of Kaiser Permanente Southern California, researchers identified 3,863 individuals with at least one ICD-9 code for MS between Jan. 1, 2008, and Dec. 31, 2010. Mean age was 52, and there was a preponderance of women (77% overall), especially among Black (81.2%) and Asian/Pacific Islander (83.6%) subgroups, and to a lesser extent among white (76.3%) or Hispanic (74.5%) individuals with MS.

"MS prevalence was highest between the ages of 35 and 64 years and declined after 65, across all racial and ethnic groups," authors wrote. While the crude disease prevalence was low among those ages 18-24, it was higher in young Black and Hispanic adults than in white individuals, and was lowest in young Asian/Pacific Islander individuals (48.5, 25.0, 18.0 and 7.1/100,000, respectively).

Although susceptibility and prevalence of MS among Hispanic or Asian individuals from different backgrounds has yet to be determined, the comparatively higher prevalence of MS among young Hispanic adults versus young white adults and significantly lower rates in older Hispanic adults compared with white adults "is consistent with emerging disease hypotheses," researchers noted. In any case, this "rapidly growing racial and ethnic group ... is projected to account for 28% of the US population by 2060," and thus will likely bear an increasing burden of disease.

The reported incidence of MS among Asian adults was significantly lower than that of white adults in this study, as well as one in Canada, the group noted:

"Intriguingly, the reported a doubling in the incidence of MS among Asian females from 0.71/100,000 in 2005 to 2.08/100,000 in 2006-2010 but no change in males," a finding that reflects the high female-to-male ratio (4.0) seen in the current study, and which deserves investigation.

Referencing their that MS incidence was highest in Black women and significantly lower in Hispanic and Asian individuals residing in Southern California, Langer-Gould and colleagues said "understanding whether similar differences exist in MS prevalence in the US has important policy and resource allocation implications, as an increasing proportion of inhabitants identify as non-white."

"A main limitation of this [type of] study is that the terms Hispanic, Asian, Black and white are socially constructed labels that influence social standing and opportunities for advancement in the US, not uniform biological or even cultural differences," Langer-Gould said. "It's crucial that new research addresses systemic bias in medical research."

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