Intrinsic race differences in ALS survival in a US clinic population independent of ventilation

Amyotrophic lateral sclerosis (ALS) incidence is lower in African Americans (AAs) and Hispanics than in Caucasians (CAUs). Initially, this observation was ascribed to reduced case-finding or underreferral of minorities to ALS clinics. However, this observation has been confirmed in population-based studies^1,2; in the First Gulf War veterans study,³ where case finding was proactive and access to care universal; and in the National Mortality Study.⁴ A second observation has been that AAs with ALS survive longer. Data from New Jersey² showed an AA ALS age-adjusted incidence of 0.88 per 100,000 per year compared to 1.80 for CAUs (50% lower), and an AA ALS age-adjusted point prevalence of 2.93 compared to 4.62 for CAUs (35% lower), with no overlap of the 95% confidence intervals. This implied an approximately 25% longer mean duration of disease from onset. A follow-up study⁵ in the incident cohort showed that median survival from diagnosis of AA patients was 41 months compared to 20 months for CAU patients. A multivariate analysis showed that age accounted for some of the difference; after adjusting for age, the protective effect of AA ethnicity on mortality was evident in the point estimate of the hazard ratio for dying (0.69), but the 95% confidence interval spanned unity (0.41–1.17). In contrast, a study from Arkansas in a clinic referral population⁶ showed lower incidence of ALS in AAs compared to CAUs, based on a clinic referral population and death certificate data, younger age at onset, and similar survival from onset.