Prevalence of disease for NMOSD estimated at 22,000 US patients

New study of 2022 data suggests rare disease is most common in Black women

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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A new study of disease prevalence estimates that about 22,000 people in the U.S. were living with neuromyelitis optica spectrum disorder (NMOSD) in 2022.

The findings also suggest that the progressive autoimmune disease is most common in Black women, as compared with other U.S. demographics. For Asian American women, the likelihood of having NMOSD was nearly two times greater than among white women.

“The prevalence of NMOSD disproportionately affects Black and Asian Americans compared to white Americans, particularly females between ages 35 and 64 years,” the researchers wrote.

The study, “Prevalence of neuromyelitis optica spectrum disorder in the United States,” was published in Multiple Sclerosis Journal.

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Physician: Making NMOSD care more equitable is achievable

Lowest prevalence of NMOSD in US found for white males

NMOSD is known to be a rare disease, but there is limited data on how common it is and on its distribution globally.

According to the Centers for Disease Control and Prevention, prevalence is defined as “the number of cases of a disease, number of infected people, or number of people with some other attribute present during a particular interval of time.”

To estimate the number of NMOSD cases in the U.S. in 2022 — meaning the disease’s 2022 prevalence — two scientists from the University of Miami School of Medicine analyzed electronic health record data from 25.7 million people who had healthcare visits that year. The data came from a large database by the company TriNetX that involves 55 healthcare organizations spanning all U.S. states.

The results showed that 1,772 people had a diagnosis of NMOSD in 2022. Mathematically, that works out to a prevalence rate of slightly less than 7 of every 100,000 people, which is higher than previous estimates, the researchers noted.

Whether this is because NMOSD is becoming more common, or just because more patients are getting accurate diagnoses remains unclear, they stressed.

Importantly, NMOSD prevalence was found to vary across racial groups: It was most common in Black Americans, affecting nearly 13 per 100,000 people. That compared with 9 per 100,000 Asian American people, and 5 per 100,000 white Americans.

The prevalence of the disease also varied by sex. Like most autoimmune diseases, NMOSD disproportionately affects women and girls, with about 9 of 100,000 females having the disease compared with about three per 100,000 males.

While prevalence did not differ significantly by race among males, Black or Asian females were about two times more likely to have NMOSD than were white females. Being a Black person again was linked to the highest likelihood of the disease.

Among white Americans, females were about twice as likely to have NMOSD as males. But for Black or Asian Americans, females were more than four times as likely to have NMOSD compared with males of the same race.

These estimates may inform various clinical and observational study designs and defines the number of individuals who may benefit from available and developing NMOSD therapies.

Putting these factors together in statistical models, the researchers estimated that Black females are more than five times more likely to have NMOSD compared with white males, while Asian females are about four times as likely to have NMOSD than white males.

Reasons for these racial differences by sex aren’t clear, the researchers said, stressing a need for further studies.

People ages 35-65 showed the highest NMOSD prevalence, affecting about 12 per 100,000 females and about 9 per 100,000 males in that age range.

“White males had the lowest prevalence of NMOSD (3–5 per 100,000) across age intervals,” the researchers wrote.

Based on all these data, the age- and sex-adjusted 2022 NMOSD prevalence in the U.S. was 21,646 people — 15,413 females and 6,233 males).

“These estimates may inform various clinical and observational study designs and defines the number of individuals who may benefit from available and developing NMOSD therapies,” the researchers wrote.

“The findings may also advance dialogue on the cost of care, particularly, those related to Food and Drug Administration (FDA)-approved medications,” the team noted.