Body Mass Index, Body Cell Mass, and 4‐Year All‐Cause Mortality Risk in Older Nursing Home Residents

Abstract

Objectives: To investigate the relationship between body composition (assessed using body mass index (BMI) and body cell mass (BCM)) and all-cause mortality in a sample of older nursing home residents. Design: Prospective study with a median follow-up period of 3.5 years. Setting: Istituto di Riposo per Anziani, Padua, Italy. Participants: A total of 344 participants (79.1% women) aged 65 and older at baseline. Measurements: Anthropometric, nutritional, and metabolic parameters were measured at baseline. BCM was measured using tetrapolar bioelectric impedance analysis. Up to 4 years of follow-up data for vital status were available. Survival analysis was conducted using Kaplan-Meier curves and multivariate Cox proportional hazards models. Results: During the follow-up period, there were 179 deaths. After adjustment for age and sex, subjects with low BMI and low BCM (lowest sex-specific tertiles) had significantly higher mortality than those with higher BMI or BCM levels. In a fully adjusted regression model, there was no association between BMI levels and risk of mortality, with subjects in the top tertile having the same likelihood of mortality as subjects in the lowest tertile (relative risk (RR)=0.94, 95% confidence interval (CI)=0.61–1.43). Conversely, there was a strong and significant inverse association between BCM levels and mortality (RR for tertile III=0.55, 95% CI=0.35–0.87; P<.01). Furthermore, participants who had high BCM had comparable survival rates in all BMI tertiles. Conclusion: In this sample of older nursing home residents, BCM was a strong and independent risk factor for mortality. BCM assessment might provide more useful prognostic information for clinicians than BMI.