Incidence and prevalence of neuromyelitis optica spectrum disorder in a contemporary, multi-ethnic cohort

Background: Ecological comparisons suggest that neuromyelitis optic spectrum disorder (NMOSD) is more common in African Caribbean and Asian compared to White people. Objective: The aim is to rigorously assess susceptibility across multiple racial and ethnic groups from the same cohort. Methods: We conducted a retrospective cohort study of > 39 million person-years of observation from members of Kaiser Permanente Southern California. The electronic health records of individuals with at least one International Classification of Diseases (ICD) code for NMOSD were reviewed to identify persons who met 2015 diagnostic criteria for NMOSD. Results: We identified 153 NMOSD cases, 105 incident and 105 prevalent. The age- and sex-standardized incidence (2013–2022) and prevalence (2019) according to the 2020 US Census per 100,000 person-years was significantly higher in Black persons (incidence = 0.90, 95% confidence interval (CI) = 0.59–1.21; prevalence = 8.44, 95% CI = 5.52–11.36) compared to all other racial and ethnic groups. The incidence was similar among Asian/Pacific Islander (0.32, 95% CI = 0.16–0.48) compared to Hispanic people (0.19, 95% CI = 0.13–0.25) and lowest in White people (incidence = 0.13, 95% CI = 0.07–0.19). Discussion: NMOSD susceptibility is highest in Black people, followed by Asian/Pacific Islands, then Hispanic people, and lowest in White people. Studies in diverse groups of minoritized people are needed to determine whether this increased susceptibility is due to shared genetic ancestry, the ill-health consequences of racism, or both.