Role of Ultrasonography in Estimating Muscle Mass in Sarcopenic Obesity

Abstract

Background: Sarcopenic obesity (SO) is the coexistence of sarcopenia and obesity in an individual. The present study is designed to define the usefulness of skeletal muscle ultrasonography (US) in the definition of SO. Methods: Eighty-nine participants aged ≥65 whose body mass index (BMI, kg/m2) was ≥30 were consecutively enrolled in an outpatient clinic of geriatric medicine. All underwent comprehensive geriatric assessment. US measurements were obtained in 6 different muscles consisting of core and limb muscles. We defined SO as the presence of low muscle function (defined by a handgrip strength < 27 kg in males and <16 kg in females) and high BMI (≥30). Results: The median age of the participants was 72 (65–85) years; 81% were female, and 35% (n = 31) had SO. Anthropometric parameters that estimate muscle mass were lower in the sarcopenic group, but estimations of muscle mass with bioelectrical impedance analysis (BIA) did not differ between groups. All US estimations of muscle mass were lower in sarcopenic obese participants, albeit not all significantly. RF muscle cross-sectional area (RF CSA) and abdominal subcutaneous fat thickness were most strongly correlated with grip strength (r = 0.477 and r = −508, respectively). Receiver operating characteristic analysis suggested that the optimum cutoff point of RF CSA for SO was ≤5.22 cm2, with 95.8% sensitivity and 46.7% specificity (area under the curve: 0.686). Conclusions: US evaluation of muscle mass may be more accurate than BIA-derived skeletal muscle index assessment for the diagnosis of SO.