Body mass index, waist circumference, and waist-to-hip ratio as predictors of mortality in nonagenarians: the Vitality 90+ Study.

BACKGROUND: The associations of body mass index (BMI) and abdominal obesity with mortality among very old people are poorly known. The purpose of this study was to investigate the association of BMI, waist circumference (WC), and waist-to-hip ratio with mortality in nonagenarians.

METHODS: This study is part of a prospective population-based study, Vitality 90+, including both community-dwelling and institutionalized persons from Tampere, Finland. Altogether 192 women and 65 men aged 90 years were subjected to anthropometric measurements, a baseline interview, and a 4-year mortality follow-up. Cox proportional hazards models were used in the statistical analyses.

RESULTS: In men, normal weight indicated a three times higher mortality risk (hazard ratio [HR] 3.09, 95% confidence interval [CI] 1.35-7.06) compared with overweight, and WC was inversely associated with mortality (HR 0.96, 95% CI 0.93-1.00) after adjustment for covariates. In women, the univariate waist-to-hip ratio (HR 1.43, 95% CI 1.06-1.92) and BMI-adjusted waist-to-hip ratio (HR 1.45, 95% CI 1.07-1.97) were positively associated with mortality. Also, overweight women whose WC was <86 cm had lower mortality than normal weight women with similar WC (HR 0.34, 95% CI 0.12-0.97).

CONCLUSIONS: In nonagenarian men, low BMI and low WC predict increased mortality. In nonagenarian women, waist-to-hip ratio alone and adjusted for BMI is positively associated with mortality. The potential positive effects of overweight combined with WC warrant more detailed analyses in larger data. In all, future studies are needed to better understand the health and functional consequences of body composition among the oldest old.