Abstract 027: Skeletal Muscle Adipose Tissue Infiltration is Associated with Mortality in Older Men
Background: Emerging evidence suggests that myosteatosis (adipose tissue (AT) infiltration within skeletal muscle (intra-muscular AT) and within the fascia surrounding skeletal muscle (inter-muscular, visible AT), increases with aging, and is positively associated with cardiovascular disease (CVD) risk factors independent of overall adiposity. Studies examining this important fat depot and mortality are lacking.
Methods: We evaluated the association of mortality (all-cause, CVD, and non-CVD) with BMI, peripheral quantitative computed tomography (QCT) measured components of lower leg skeletal muscle adiposity (total, subcutaneous, and intermuscular AT, and muscle attenuation), and dual-energy X-ray absorptiometry (DXA) measured total body and trunk fat in 1155 community-dwelling older men (mean age 77.2 ± 5.1 years). Date and cause of death from death certificates were reviewed by a central physician adjudicator, with cause of death classified by ICD9 codes. Cox proportional hazards models were used to estimate the risk of mortality. Stepwise regression was used to select significant covariates for multivariable models. We tested the following covariates: age, race, study site, lifestyle risk factors, DXA total body fat, skeletal muscle area, height, diabetes, hypertension, stroke, myocardial infarction, renal disease, cancer, lipids, and medications that may influence metabolism.
Results: During a mean follow-up of 5.9 years (2005-2012), 246 participants died. Among these, 74 participants died from CVD, and 159 died from non-CVD causes (cancer and other causes). After adjustment for significant covariates, lower intra-muscular AT infiltration, as reflected by greater skeletal muscle attenuation, was associated with decreased all-cause mortality, decreased CVD mortality, and decreased non-CVD mortality (Hazard ratio [95% CI] per SD increase in skeletal muscle attenuation: 0.77 [0.67, 0.90], 0.72 [0.55, 0.94], and 0.81 [0.67, 0.97], respectively; all P-values <0.02). No other measures of peripheral QCT and DXA measured adiposity or generalized obesity (BMI) were associated with mortality, regardless of the degree of adjustment.
Conclusion: Our study revealed a previously unreported, independent association between myosteatosis and mortality among older men. Further studies are needed to establish if the association of myosteatosis with mortality is independent of inflammation, insulin resistance, visceral and other ectopic fat depots, and to identify possible biological mechanisms underlying this relationship.
- © 2013 by American Heart Association, Inc.