Body Composition Changes and 10-Year Mortality Risk in Older Brazilian Adults: Analysis of Prospective Data from the SABE Study.

Abstract

Aging related alterations in body composition are associated with higher all-cause mortality risk. To examine the associations between 10-year mortality risk with both BMI and body composition, as well as to establish whether these relationships are modified by age and gender, using data from community-dwelling older Brazilian adults. We used data from two waves i.e., 2000 and 2010 of the SABE (Health, Well-being, and Aging) study conducted in São Paulo, Brazil, involving a probabilistic sample of community-dwelling older adults aged 60 years and older. The variables of the study were: mortality (in 10-year follow-up period), body mass index (BMI), body composition (waist circumference, waist hip ratio, triceps skinfold thickness, mid-upper arm circumference, calf circumference, and arm muscle area) and covariables (sociodemographic characteristics, life style, self-reported health conditions, number of chronic diseases, Mini mental state exam, and Geriatric depression scale). Poisson regression estimates with STATA statistical software were used for statistical analyses, considering all p-values < 0.05. Over the 10-year follow-up period, there were 769 deaths (40.2%). The mortality rate was 61.0 for men and 111.8 for the ≥80 age group. In the fully adjusted model, statistically significant hazard ratios were found for low muscle mass (IRR: 1.33), underweight (IRR: 1.29), and low fat mass (IRR: 1.31) with mortality. Men in extreme BMI categories (underweight - IRR: 1.47; obesity I - IRR: 1.66; and obesity II - IRR: 1.91) and women with low muscle and low fat mass were significantly associated with mortality risk. In the ≥80 age group it was observed that low muscle mass (IRR: 168.7), inadequate body reserves (IRR: 1.63), low fat mass (IRR: 140.7), and underweight (IRR: 142.9) were associated with mortality risk. Waist circumference demonstrated protection for mortality in the high-risk categorization for the ≥80 age group. Our results showed that underweight, low fat mass, and low muscle mass were associated with mortality risk, presenting different roles considering gender and age in older Brazilian adults over a 10-year follow-up period.