Intermuscular adipose tissue or intramuscular adipose tissue content, which affects skeletal muscle density more? -a study based on abdominal opportunistic CT

Abstract To explore intermuscular adipose tissue (IMAT) and intramuscular adipose tissue content (IMAC) which affect skeletal muscle density (SMD) more and elucidate its underlying causes. 292 inpatients without definite musculoskeletal system disease were recruited. All the patients performed abdominal CT. Muscle parameters which included skeletal muscle area (SMA), skeletal muscle index (SMI), SMD, IMAC and IMAT, and fat parameters which included area of subcutaneous fat tissue in abdominal wall were measured by two musculoskeletal radiologists with Image J software at the level of L3 vertebrae. Multiple regression analysis was used to identify the factors which affected SMD, and compared the extent of influence. SMD was highly correlated with IMAT and IMAC (p < 0.05), moderately correlated with gender, age and area of subcutaneous fat tissue in abdominal wall (p < 0.05), and slightly correlated with BMI (p < 0.05). Multiple linear regression analysis showed that IMAC, IMAT and age are influencing factors of SMD (p < 0.05). The order of influence degree is IMAT(Stbβ=-0.616), IMAC(Stbβ=-0.429), and age (Stbβ=-0.098). Area of subcutaneous fat tissue in abdominal wall and gender were not influence factors of SMD (p > 0.05). Age, IMAT, and IMAC exert an influence on SMD. Notably, the impact of IMAT on SMD is much more significant.