New study gives snapshot of MS in US by race, age, sex, location

Highest MS prevalence found in Black, white people in North

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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An updated snapshot of multiple sclerosis (MS) in the U.S. — provided by new population estimates from a study of insurance data — shows a greater prevalence of MS among white and Black people compared with other racial and ethnic groups.

But overall, the neurodegenerative disorder has become more common — and affects a much wider range of people — than ever before.

“In the United States, MS has become more prevalent and demographically diverse,” the researchers wrote, adding, “These data are important for clinicians, researchers, and policy makers.”

The analysis also found that the disease particularly affects people in the 45-64 age range, and that there are more people with MS living in northern regions of the U.S. compared with southern areas of the country.

The study, “Population-Based Estimates for the Prevalence of Multiple Sclerosis in the United States by Race, Ethnicity, Age, Sex, and Geographic Region,” was published in JAMA Neurology. The work was funded by the National Multiple Sclerosis Society.

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Study on MS prevalence in US only included insured patients

MS can affect people of any background, but the disease is more common in some racial groups compared with others. Recent studies suggest that the incidence of MS — that is, the number of people newly diagnosed with the disease — is higher among Black people compared with those of other racial backgrounds.

However, the prevalence of MS in the U.S., meaning the number of people currently living with the disorder, has not been estimated.

With the aim of filling this knowledge gap, the National MS Society formed a workgroup with researchers from several U.S. universities, the U.S. Department of Veterans Affairs, and medical practices, among others.

“Prevalence reflects the burden of disease in a population and is critical for clinical care, resource allocation, and policy decisions,” the team wrote.

For their estimation, the researchers collected administrative data from several large insurance companies as well as government-funded insurance programs.

The dataset was selected “to represent US private and government-sponsored insurance programs, reasoning that nearly all persons with MS (except uninsured people, Native American individuals exclusively using the Indian Health Service, and incarcerated people) would receive health services through 1 of these programs,” the team wrote.

From the data, the scientists identified 744,781 adults living with MS in the U.S. from 2008 to 2010. About three-quarters (76%) of these individuals were female, which is in line with other research showing MS is generally more common in women.

Most patients were white (77%), while 10% were Black, 7% were Hispanic, and 4% were another race. The researchers noted that, while being Hispanic is considered an ethnicity and not a racial group, it was included as a racial category in many of the insurance datasets, and therefore also for this analysis.

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Black populations found to have 2nd highest MS prevalence in US

With these numbers in hand, the researchers calculated prevalence estimates based on the makeup of the total U.S. population. Results showed the highest prevalence of MS was seen in white populations, where it was estimated that 374.8 of every 100,000 people was living with the disease. The second-highest prevalence was in Black populations, at 298.4 of every 100,000 people.

The estimated prevalence among Hispanic populations was the lowest, at 161.2 of every 100,000 people, while the estimated prevalence in the “other” category was 197.7 of 100,000 individuals.

“This study found that white individuals had the highest MS prevalence followed by Black individuals, individuals from other non-Hispanic racial and ethnic groups, and Hispanic individuals,” the researchers concluded.

Prevalence rates also varied according to age, though overall, nearly half of the MS patients in this analysis were between the ages of 45 and 64.

Among female patients of all racial backgrounds, the prevalence was highest among patients ages 45 to 54. However, the highest prevalence for male patients tended to be seen at older ages, peaking around ages 55 to 64 for most groups.

Analyses accounting for sex, age, and race showed notable differences in MS prevalence based on geographic location. Generally, the prevalence tended to be lowest in the southern parts of the U.S. and highest in the northern regions. This is in line with prior data showing that MS risk tends to increase among people who live further from the equator.

Latitude in fact played an important role in the geographic distribution of MS, with disease prevalence increasing by 16.3 cases per 100,000 with each one-degree increase in latitude. However, this increase was not uniform across all latitudes, suggesting other factors may play a role.

“Northern regions of the United States continue to have a higher prevalence of MS across racial and ethnic groups,” the scientists wrote, noting that “additional analyses are needed to examine climatological, demographic, infectious, and other factors that may contribute to this geographic variation.”

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Researchers call for better care of ‘historically underrecognized populations’

In an editorial published alongside the study, a team of scientists in the U.S. and Canada said the new data on MS prevalence will be key for ensuring better overall care for patients.

“The findings have major implications for allocation of resources to ensure research, prevention, and treatment, specifically in … historically underrecognized populations,” they wrote.

The results especially highlight the importance of recognizing the diversity of MS, they said, noting it has long been mischaracterized as a disease that mainly affects white women.

“There is a critical need for greater awareness of the prevalence and clinical burden of MS across all racial groups among the public, policy makers, and payers, in addition to physicians,” the researchers wrote.

“The stereotypical impression of MS as a disease primarily affecting women of European ancestry needs to be replaced with one that encompasses the complete spectrum of MS prevalence across racial and ethnic domains,” they wrote.

While the new study is a step forward, the researchers noted it also carriers some notable limitations — in addition to issues with conflating racial and ethnic classifications, the team highlighted a lack of data on people from other racial groups. Specifically, there was a dearth of information on MS among Asian, Pacific Islander, Middle Eastern or North African, and Indigenous populations.

The stereotypical impression of MS as a disease primarily affecting women of European ancestry needs to be replaced with one that encompasses the complete spectrum of MS prevalence across racial and ethnic domains.

The researchers also noted that the reliance on insurance data may lead to underrepresentation of groups that face more barriers to accessing medical care.

Overall, they stressed that further work is needed to understand racial and ethnic variations in MS, to enable the best care possible for patients.

“Further research and reliable epidemiological data in underrepresented groups are needed to disentangle the effects of race, genetics, environment, prescribing patterns, social determinants of health, and racism on clinical outcomes in MS and to work toward effective interventions,” they wrote.

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