Mortality risk among older adults of indigenous ancestry with asymptomatic intracranial atherosclerotic stenosis. A population-based, longitudinal prospective study in rural Ecuador

Background: Intracranial atherosclerotic stenosis (ICAS)-related mortality may vary according to race/ethnicity, but information about this association in diverse populations is limited. We aimed to assess mortality according to ICAS severity in stroke-free older adults of indigenous ancestry living in Ecuador. Methods: We invited stroke-free individuals ≥60 years old enrolled in the population-based Atahualpa Project cohort to undergo time-of-flight brain MRA. Participants were followed to ascertain mortality (as the primary outcome) during the observation period. Luminal stenosis in 11 large intracranial arteries was calculated to reflect the stenosis score. We categorized prevalent ICAS as a stenosis score ≥3 points or as the presence of moderate-to-severe stenosis (≥50 %). Cox proportional hazards models were fitted to estimate mortality risk according to ICAS severity. Results: Analysis included 358 participants (mean age: 67.5 ± 6.9 years; 57 % women) followed on average for 10.1 ± 2.9 years. Seventy-four (21 %) participants had a stenosis score ≥3 points, and 37 (10 %) had moderate-to-severe stenosis. In adjusted analysis, mortality risk was higher in participants with a ICAS score ≥3 points (HR: 2.38; 95 % C.I.: 1.49–3.80; p < 0.001) and among those with moderate-to-severe stenosis (HR: 1.96; 95 % C.I.: 1.12–3.43; p = 0.018). Thirty-five (10 %) participants had incident strokes. Overall, 97 (27 %) participants died during the follow-up, including 11/35 who developed an incident stroke and 86/323 who did not (31 % versus 27 %; p = 0.544). Discussion: The burden of asymptomatic ICAS is high in older adults of indigenous Ecuadorian ancestry and is significantly associated with mortality. Incident strokes do not influence mortality in this population.