Reduced frequency of ALS in an ethnically mixed population: a population-based mortality study.

OBJECTIVE: To describe ALS mortality rates in the well-characterized ethnically mixed Cuban population over a 6-year period.
BACKGROUND: There have been few population-based epidemiologic studies of ALS in non-Europeans. Preliminary data from the United States suggest a lower frequency of ALS in Hispanic and African groups compared with those of European descent. The Cuban population of 11 million comprises three main ancestral groups classified by skin color as white (65%), mixed (24%), and (black 10%). Medical care is of a high standard and is free. Cuba is ideally placed to establish the frequency of ALS in an admixed population of diverse ethnic origin.
METHODS: Multiple-cause mortality files from the Central Statistics office in Cuba for the years 2001 through to 2006 were searched for codes corresponding to ALS. Age-adjusted mortality rates were calculated by sex, race/ethnicity, age, and geographic region at time of death.
RESULTS: Four hundred thirty-two patients with a diagnosis of ALS were identified. The mean age at death was 63.7 years. There was a slight male predominance (1.1:1). The adjusted death rate from ALS for the total population older than 15 years was 0.83 per 100,000. The adjusted mortality rate per 100,000 was considerably lower in the mixed population (0.55; confidence interval [CI] 0.4-0.72) than in whites (0.93; CI 0.83-1.03) and blacks (0.87; CI 0.62-1.17). There was no correlation between the number of neurologists in each region and the mortality rate from ALS (r = 0.268, p = 0.335).
CONCLUSIONS: The overall mortality rate from ALS in Cuba is similar to that described in Hispanic populations in the United States and is lower than in Northern European populations. Mortality from ALS is lowest in a population of mixed ancestry. Ancestral origin is likely to play a role in ALS susceptibility.