Ethnic variation in the incidence of ALS - A systematic review

Background: The findings of recent genetic polymorphism studies in ALS suggest that the influence of genetic risk factors for the disease may vary by ethnicity. It is now widely accepted that the incidence of ALS is uniform across Caucasian populations, but whether racial variation across other ethnicities exists remains unknown. Method: Systematic review of the known literature on the incidence, prevalence, and mortality of ALS across all ethnicities. To facilitate comparison, studies were grouped according to the type of data presented and examined for sources of case ascertainment and inclusion criteria. Results: The literature search identified 61 publications. Lower standardized incidence rates were observed in Asian than Caucasian populations. Within the United States, several incidence and mortality studies have identified lower ALS frequency among African American and Hispanic populations than among non-Hispanic Caucasians. These observations are supported by the other data sources. Conclusions: The incidence of ALS may be lower among African, Asian, and Hispanic ethnicities than among whites. We conclude with proposals for a prospective epidemiologic study concentrating on non-Caucasian populations.