Background: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathy characterized by aquaporin-4 antibodies, whose prognosis is influenced by onset age, race, environmental exposures and immunosuppression. Distinguishing the contribution of environment from genetics is challenging. We aimed to compare neuromyelitis optica spectrum disorder (NMOSD) patient outcomes according to self-identified racial group and place of residence. Methods: This retrospective analysis of prospectively collected data included non-white anti-aquaporin-4 antibody positive NMOSD patients under follow-up from 15 centers [United Kingdom, France, Germany, Denmark, Martinique, United States of America, Japan, South Korea, Singapore, Thailand, China (including Hong Kong) and India]. Racial groups were designated: African/Caribbean; South Asian; East Asian (including Southeast Asia). Patients from these racial groups residing outside Africa/Caribbean or Asia were compared with those living in the Caribbean or the Asian areas. Kaplan-Meier survival curves and Cox models were generated using time to sustained Expanded Disability Status Scale≥6.0 or death; time to sustained Kurtzke Visual Function Score≥3.0 or a composite endpoint of all three. Results: Among 821 patients, African/Caribbean patients (n = 206) had the shortest time to immunosuppression and higher visual disability at onset. South Asian patients (n = 65) were younger, had lower visual disability at onset and higher mortality rate. East Asians (n = 550) had the lowest relapse rate and lowest accrued motor disability. Survival analysis of African/Caribbean outside Africa/Caribbean vs those in the Caribbean showed a significant difference in the composite endpoint (p = 0.024,log-rank test), not apparently related to treatment differences. No significant differences between native and those residing outside Asia were found for other racial groups. Conclusion: This NMOSD study reports the effects of place of residence on the outcomes in different races. Place of residence may not be a significant driver of disability among Asian patients, while it may influence African/Caribbean patient outcomes. Validating these findings could help distinguish between genetic causes and potentially modifiable environmental factors.
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