Chagas disease and mortality in old age as an emerging issue: 10 year follow-up of the Bambuí population-based cohort study (Brazil)

Earlier studies of the natural history of Chagas disease (ChD), which is caused by the protozoan Trypanosoma cruzi, had suggested that the consequences of the disease in the elderly are negligible. The objective of this study was to estimate long-term mortality in ChD in old age using data from a large population-based cohort study. The study was conducted in Bambui City (~15,000 inhabitants), Brazil. Participants were 1479 residents aged 60 years and over (84.9% from total), who were followed from 1997 to 2007. During a mean follow-up of 8.72 years, 567 participants died, resulting in a total of 12,896 person-years observation. The baseline prevalence of T. cruzi infection was 38.1%. T. cruzi infection was a strong predictor of mortality among cohort members, and this association remained largely significant after adjustments for age, sex, and conventional cardiovascular risk factors (hazard ratio [HR] = 1.56; 95% CI 1.32-1.85). Increased risks for mortality associated with T. cruzi infection were consistently observed in those aged 60-69 (HR= 1.79; 95%CI 1.37-1.85), 70-79 (HR=1.35; 95% CI 1.04-1.76) and 80 years and over (HR= 1.59; 95% CI 1.09-2.33). Overall, population attributable risk for mortality due to T. cruzi infection was 13.2% (95% CI 9.8-16.4). Our results indicate that ChD is a relevant individual and population health issue in old age, supporting the need for measures to reduce the burden of ChD in this growing segment of the population.