Factors associated with skeletal muscle mass in patients with Behçet’s disease: An exploratory study

Abstract Objectives To investigate the prevalence of low skeletal muscle mass and factors associated with skeletal muscle mass index (SMI) in Japanese outpatients with Behçet's disease (BD), while assessing sarcopenia according to the Asian Working Group for Sarcopenia 2025 criteria. Methods This cross-sectional study included ambulatory outpatients with BD aged ≥40 years. SMI was measured using multifrequency bioelectrical impedance analysis. Sarcopenia was defined as low SMI with low handgrip strength. Clinical characteristics, physical functions, nutrition- and body composition-related measures, rectus femoris ultrasonography, and laboratory parameters were compared between the low- and normal-SMI groups. Associations with SMI were examined using age- and sex-adjusted and domain-specific multivariable linear regression models. Results Among 48 patients (mean age: 65.4±11.8 years; 45.8% women), 52.1% had Low SMI, and 10.6% of 47 participants with available SMI and handgrip strength data had sarcopenia. In multivariable analyses, higher SMI remained associated with higher body mass index, greater handgrip strength, larger calf circumference, higher phase angle, and greater rectus femoris muscle thickness. Conclusions Low skeletal muscle mass is common in BD ambulatory outpatients and is associated with muscle-, nutrition-, and body composition-related measures. However, clear associations with disease activity and current systemic glucocorticoid use were not observed.