Multiple sclerosis in Indigenous Peoples of the Americas: A systematic review of incidence, prevalence, and outcomes.

Introduction: The incidence, prevalence and outcomes of multiple sclerosis (MS) are unclear in Indigenous Peoples (IP) who are more likely to be underrepresented in research. We completed a systematic review of MS in IP of the Americas.

Methods: A systematic review was conducted using PubMed, Web of Science, and Cochrane databases as well as references of retrieved papers. Inclusion criteria were: peer-reviewed publications (January 1990- December 2021), incidence, prevalence, or clinical outcome measures of MS in self-identified IP in the Americas. Incidence, prevalence, morbidity and mortality data were summarized and stratified by location and year of publication. Study quality was evaluated by risk of bias or confounding.

Results: Out of 416 titles, thirteen studies met inclusion criteria. Four studies evaluated incidence, seven prevalence, three clinical outcomes and one mortality. Most studies were completed in Canada or the United States (US). Incidence rates per 100,000 ranged from 0.48 (in US Indian Health Service records) to 8.15 (First Nations Manitoban Canadians). Prevalence ranged from 0 (Lacandonian Mexicans and Panamanians) to 188.5 (First Nations Manitoban Canadians). Incidence and prevalence are consistently lower in IP than comparator White populations. IP with MS were reported to have higher disability and faster disability progression than non-Indigenous comparators. MS-related mortality is low compared to White people.

Conclusion: There is an absence of high-quality studies evaluating MS in IP. Available evidence indicates low, but increasing incidence and prevalence of MS in IP of the Americas. IP with MS may have worse disability than non-Indigenous comparators. Future studies should evaluate the factors influencing the increases in incidence and prevalence as well as better characterize possible disparities in MS care among IP.