Body mass index and mortality among community-dwelling elderly of Southern Brazil

This study aims to measure the association between body mass index (BMI), comparing two different classifications, and mortality among community-dwelling elderly considering myopenia in Pelotas, Brazil. This is a longitudinal study started in 2014, we followed 1451 elderly people (≥ 60 years) enrolled in the “COMO VAI?” study. BMI was classified according to the World Health Organization (WHO) and the classification with specific cutoff points for older adults. Myopenia was measured by calf circumference (≤33 cm for women and ≤34 cm for men). Cox proportional-hazards models were used to test associations controlling for sociodemographic and behavioral characteristics and number of morbidities. Nearly 10% (N = 145) of the elderly died during almost three years of follow-up. We observed a L-shaped relation between BMI and mortality. Elderly with underweight had a higher mortality risk compared to those with adequate BMI in both classifications. According to the WHO classification, overweight elderly presented protection for mortality (HR: 0.58; 95% CI 0.38–0.87) when compared to those with adequate BMI. Among elderly with myopenia, overweight by WHO continued to protect against mortality, although not significantly, while those with the specific classification underweight presented a higher risk of death compared to those with normal weight (HR: 2.09; 95% CI 1.06–4.14). In conclusion the underweight increased the risk of death in community-dwelling elderly people during a follow-up of three years. The specific classification seemed to be more adequate to indicate risk of mortality in this population. Higher BMI protect against mortality when muscle mass was not considered. •Among elderly people with myopenia, presented higher risk of death than those without myopenia.•We could identify a L-shaped pattern between BMI and mortality observed in nearly three years of follow-up.•Elderly with BMI below 22 kg/m2 presented higher mortality risk than the observed among individuals with higher BMI values.•The protection of the BMI for mortality risk progressively increases until around 30 kg/m2.