Índice de massa corporal e mortalidade entre idosos comunitários do sul do Brasil

Abstract

This study is part of the “COMO VAI” a cohort study. The aim of this study was to evaluate the association between body mass index (BMI) and mortality among community-dwelling older adults in a period of up to 3 years of follow-up, observing the differences between cut-off points proposed by the World Health Organization (WHO) - low weight: BMI <18.5 kg / m2; normal weight: BMI ≥ 18.5 and < 25.0 kg / m2; overweight: BMI ≥ 25.0 kg / m2; and by Lipschitz – low weight: BMI < 22.0 kg / 222 m ; normal weight: BMI ≥ 22.0 and ≤ 27.0 kg / m ; overweight: BMI > 27.0 kg / m . The collection of socioeconomic, demographic and health characteristics, in addition to the anthropometric measurements, was carried out in 2004 at the individuals’ households. Weight was measured using a digital scale and standing height was estimated from the knee height. A total of 1,451 older individuals were interviewed (1,364 provided BMI). Follow-up occurred in 2016-7 based on phone calls or home interviews, with verification of deaths from household contact and also from Epidemiological Surveillance Service of the municipality. Crude and adjusted analyses were run using Cox Regression (proportional hazards regression), and the hazard ratios (HR) of mortality and their respective 95% confidence intervals were established (CI95%). Age, sex, schooling, skin color, economic status, marital status, alcohol consumption, physical activity, smoking and number of morbidities were considered as possible confounders. The low amount of muscle mass (miopenia) was evaluated from the calf circumference. Around 10% of elderly died in approximately three years of follow-up. Those older individuals classified as underweight according to the WHO classification had about twice higher risk of mortality compared to the eutrophic group (HR: 2.18; CI95% 1.02-4.70), a similar result was observed when using the cut-off points recommended by Lipschitz (HR: 1.80; CI95% 1.03-3.17). Individuals classified with overweight according to the WHO classification had lower risk of mortality (HR: 0.58; CI95% 0.38-0.87) when compared to the eutrophic ones. There was no statistically significant difference in mortality risk among overweight elderly individuals by the Lipschitz classification in relation to normal weight. Results were not statistically significant after stratification for the presence low muscle mass (assessed by calf circumference). From these results it was possible to conclude that underweight increased the risk of mortality observed in up to three years of follow-up among community-dwelling older adults, while overweight to a certain extent was a protective factor to mortality. Nutritional evaluation of the elderly should not only consider BMI, but also muscle mass; even it is obtained using simple measurements. This volume includes: the research project, followed by the field work report, changes performed at the research project, the original article and the rules of Public Health Nutrition - the article from this dissertation will be submitted to this journal.