Introduction: Aging related alterations in body composition are associated with higher all-cause mortality risk.
Objective: 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.
Methods: 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.
Results: 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.
Conclusion: 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.
Keywords: Aging; body composition; community-dwelling; mortality.