SEATTLE – These populations often have more severe disease, likely driven by socioeconomic factors and health care access, according to a new study that examined neighborhood-level data and disease severity in the United States.
“It has previously been thought that MS is less common among non-European Caucasian White populations, driven partly by the well-known association of incidence with latitude. It is abundantly clear at this point that this idea is not true,” said Christopher Orlando, MD, during a presentation at the 2022 annual meeting of the American Academy of Neurology.
He noted that several U.S. studies with large sample sizes have shown greater disease severity and a higher disability burden among Hispanic and Black patients. “Black patients in particular appear to have a higher incidence of disease and a greater proportion of progressive disease phenotypes,” said Dr. Orlando.
Race and ethnicity are unlikely explanations for this disparity, according to 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].”
Instead, evidence suggests that interrelated social causes include access to resources, environmental exposures, and psychosocial stress. “These affect health via a number of pathways including direct physical injury, allostatic load, and access to health care,” said Dr. Orlando.
Probing racial and ethnic disparities
Previous studies that corrected for social determinants of health such as socioeconomic and insurance status reduce the association between MS disability and race, but they do not completely explain it.
To get a better understanding of the impacts of these factors, researchers have used neighborhood-level data combined with information on socioeconomic status and social deprivation to identify associations with MS severity.
At the conference, Dr. Orlando presented a new study that is the first to use this methodology in the United States, and it is the first to apply it to the study of racial and ethnic disparities in MS.
The study confirmed more severe disability in Hispanic and Black patients than in White patients. Clinical factors associated with more severe disease were similar across the three groups, with some small differences among individual traits. “More stark differences appeared when we compared social determinants of health. 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%],” said Dr. Orlando.
The researchers found that Black and Hispanic patients tend to live in more vulnerable neighborhoods than White patients. The researchers found no significant association between social vulnerability index (SVI) values and MS severity, though there was an association in a separate analysis that only included White patients. The SVI uses 15 measures taken from the U.S. Census to identify communities that might require additional support during natural disasters.
“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,” said Dr. Orlando.