Body mass index (BMI), body composition and mortality of nursing home elderly residents

The body mass index (BMI) is a key marker of nutritional status among older patients, but does not reflect changes in body composition, The aim of the present study was to investigate BMI levels and body composition in a sample of disabled nursing home residents, and to study possible interrelations between BMI, fat-free body mass (FFM), body fat mass (BFM), skeletal muscle mass (SMM) and 1-year mortality rates. FFM and SMM were assessed by 24-h urine creatinine excretion and BFM as the difference between BMI and FFM. We calculated relative risk (RR) and odds ratio (OR) of 1-year mortality, associated with different levels of BMI, FFM index (where index=value/height²), SMM index and BFM index in 82 disabled institutionalized elderly patients. One-year mortality rate was 29.3%. Adjusted relative risk of mortality of low BMI patients was 1.45 (95% CI=0.73-2.89; OR=1.73) and 0.63 (95% CI=0.33-1.60; OR=0.72) in high BMI. Risk of mortality was higher in those having low FMM index or SMM index (RR=2.42, 95% CI=0.36-16.18; OR=2.55 and RR=3.22, 95% CI=0.78-13.32; OR=3.67, respectively). It is concluded that low FFM and SMM indexes among disabled nursing home residents are far better predictors than BMI for 1-year mortality estimation.