Incidence of amyotrophic lateral sclerosis among American Indians and Alaska natives.

ABSTRACT

IMPORTANCE More thorough evaluation of amyotrophic lateral sclerosis (ALS) and motor neuron disease in unique populations could provide clues to etiologies for these idiopathic conditions, and educational programs for American Indian and Alaska Native (AI/AN) people and health care professionals on reservations could improve awareness, understanding, diagnosis, and treatment. In the ongoing search for susceptibility genes, studying particular racial groups, such as AI/ANs,might facilitate the identification of new mutations. OBJECTIVE: To provide better understanding of ALS and secondarily of motor neuron disease among AI/AN people by estimating the incidence and prevalence among AI/ANs served by the Indian Health Service health care system. DESIGN AND SETTING: Analysis of electronic records for AI/ANs with ALS and with motor neuron disease separately for the calendar years 2002-2009 using inpatient and outpatient visit data from the Indian Health Service, which provides health care to eligible AI/ANs nationwide. PARTICIPANTS: Cases were defined by at least 2 inpatient or outpatient visits with the diagnosis. MAIN OUTCOME MEASURES: Crude and age-adjusted incidence and prevalence rates were calculated. RESULTS: Seventy-one AI/ANs were diagnosed with ALS, yielding an average annual crude incidence rate of 0.63 cases per 100 000 and an age-adjusted incidence of 0.92. The median age at onset was 56.0 years and was higher among women than men (62.0 vs 55.0 years; P=.06). Age-specific incidence increased to 70 to 74 years. The crude and age-adjusted point prevalence rates were 2.00 and 4.12, respectively. The crude and age-adjusted incidence rates for motor neuron disease were 1.08 and 1.50, respectively. The annual rates were unchanged across the study period. CONCLUSIONS AND RELEVANCE The incidence of ALS among AI/ANs appears to be lower than that reported for white populations, a finding congruent with reports of other minority populations. Community-based studies are important to confirm these findings and to examine reasons for the low rate of ALS among AI/ANs.