Muscle Density, Not Size, Is Inversely Associated With All-cause Mortality: The Multi-Ethnic Study Of Atherosclerosis

Abstract

PURPOSE: Little is known about associations between lean muscle and mortality in healthy adults. The purpose of this study was to evaluate associations between abdominal muscle quantity (area) and quality (density) with risk of all-cause mortality in a diverse cohort. METHODS: Abdominal muscle area and density were measured in men (n=946) and women (n=955) from the Multi-Ethnic Study of Atherosclerosis using computed tomography scans at the L2-L4 spinal column, with muscle density scored as attenuation in Hounsfield units. Sex-stratified cox proportional hazard models were used to assess risk of all-cause mortality across sex-specific quartiles of muscle area and density adjusting for confounders, with area and density entered simultaneously. RESULTS: Mean age for men and women at baseline was 64.2 and 65.1 and median follow-up time was 10.6 and 10.9 years, respectively. The mortality rate for men was higher than for women (19.9% vs. 12.5%). Hazard ratios of all-cause mortality by quartiles of muscle area and density are shown in Table 1. For muscle density there was an inverse dose response with mortality, such that men and women in the highest quartiles of muscle density had 73% and 57% lower risk of mortality, respectively, in fully adjusted models compared to those in the lowest quartiles. There was no association between muscle area and mortality. CONCLUSIONS: In a large, diverse cohort of men and women, greater abdominal muscle density, but not muscle size, was associated with a markedly lower risk of all-cause mortality with over a decade of follow up. These results highlight muscle quality as a powerful predictor of mortality in relatively healthy community dwelling adults. Future studies are needed to investigate biological mechanisms linking skeletal muscle fat infiltration with mortality.