Muscle area and density and risk of all-cause mortality: The Multi-Ethnic Study of Atherosclerosis.

Background: Lean muscle plays critical roles in physical functioning and metabolism. However, little is known regarding associations between muscle and mortality in adults.

Objective: The purpose was to evaluate associations between abdominal muscle quantity (area) and quality (density) with risk of all-cause mortality in a diverse cohort free of cardiovascular disease.

Design: Data were taken from the Abdominal Body Composition, Inflammation, and Cardiovascular Disease ancillary study of the Multi-Ethnic Study of Atherosclerosis prospective cohort study. Participants were adults (45-85 years) free of extant cardiovascular disease, and of Hispanic, African American, Chinese, or Caucasian descent. Of the original 6814 MESA participants, a random, representative sample (n = 1974) participated in the ancillary body composition study. Abdominal muscle area and density were measured from computed tomography scans spanning L2-L4. Muscle density was measured as attenuation in Hounsfield units, and area was quantified as cm. Gender-stratified cox proportional hazard models assessed the risk of all-cause mortality across gender-specific quartiles of muscle area and density adjusting for confounders, with area and density entered simultaneously.

Results: At baseline, the mean age for men (n = 946) and women (n = 955) was 61.5 and 62.5 years and median follow-up time was 10.6 and 10.9 years, respectively. Muscle density was inversely associated with mortality, with the highest quartile of density showing a 73% reduction in risk for men (HR = 0.27, 95% CI = 0.14-0.51; p-trend<0.001) and 57% reduction for women (HR = 0.43, 95% CI = 0.18-1.01; p-trend = 0.04) compared to the lowest quartile when adjusting for mortality risk factors, lifestyle, BMI and visceral fat. There was no association between muscle area and all-cause mortality for men (p-trend = 0.58) or women (p-trend = 0.47).

Conclusions: Greater abdominal muscle density, but not muscle area, is associated with markedly lower risk of all-cause mortality across a decade of follow up. Muscle quality may be a powerful predictor of mortality in community dwelling adults.