Decreased muscle mass and increased central adiposity are independently related to mortality in older men

Abstract

Background: Aging is associated with significant changes in body composition. Body mass index (BMI; in kg/m2) is not an accurate indicator of overweight and obesity in the elderly. Objective: We examined the relation between other anthropometric indexes of body composition (both muscle mass and body fat) and all-cause mortality in men aged 60-79 y. Design: The study was a prospective study of 4107 men aged 60-79 y with no diagnosis of heart failure and who were followed for a mean period of 6 y, during which time there were 713 deaths. Results: Underweight men (BMI < 18.5) had exceptionally high mortality rates. After the exclusion of these men, increased adiposity [BMI, waist circumference (WC), and waist-to-hip ratio] showed little relation with mortality after adjustment for lifestyle characteristics. Muscle mass [indicated by midarm muscle circumference (MAMC)]was significantly and inversely associated with mortality. After adjustment for MAMC, obesity markers, particularly high WC (>102 cm) and waist-to-hip ratio (top quartile), were associated with increased mortality. A composite measure of MAMC and WC most effectively predicted mortality. Men with low WC (≤102 cm) and above-median muscle mass showed the lowest mortality risk. Men with WC > 102 cm and above-median muscle mass showed significantly increased mortality [age-adjusted relative risk: 1.36; 95% CI: 1.07, 1.74), and this increased to 1.55 (95% CI: 1.01, 2.39) in those with WC > 102 and low MAMC. Conclusion: The findings suggest that the combined use of both WC and MAMC provides simple measures of body composition to assess mortality risk in older men. © 2007 American Society for Nutrition.