Association of phase angle with malnutrition and sarcopenia in interstitial lung disease: a cross-sectional analysis of body composition and functional decline

Interstitial Lung Disease (ILD) patients frequently develop malnutrition and sarcopenia. Phase angle (PA), a nutritional biomarker, may predict these conditions, though its clinical utility in ILD remains undetermined. This study evaluated the association of phase angle with malnutrition and sarcopenia in patients with ILD. A total of 105 hospitalized patients with ILD were prospectively and consecutively enrolled and analyzed in this observational study. Each participant underwent a comprehensive assessment including detailed anthropometric measurements and body composition analysis. Nutritional status was evaluated according to the GLIM criteria to diagnose malnutrition, and sarcopenia was identified based on the AWGS 2019 consensus. Participants were then dichotomized into a low phase angle group (< 5.0°for males; <4.6°for females) and a normal phase angle group (≥ 5.0°for males; ≥4.6°for females) using established cut-off values. Body composition and functional parameters were compared between the two groups. Finally, multivariate logistic regression analysis was performed to identify factors independently associated with phase angle. The prevalence of malnutrition and sarcopenia was 39.0% and 30.4%, respectively. The low PA group demonstrated significantly poorer outcomes across all measured parameters (P < 0.05), including: (1) Body composition: reduced intracellular water, protein, skeletal muscle mass, BMI, and SMI; (2) Physical function: decreased handgrip strength, mid-upper arm circumference, knee extension strength, 6-minute walk distance, 6-meter gait speed, and SPPB scores. Gender-specific analyses revealed consistent patterns. PA strongly correlated with key nutritional and functional markers. PA was significantly negatively correlated with malnutrition (unadjusted OR = 0.307, 95% CI: 0.178–0.531; adjusted OR range: 0.408–0.414, all P < 0.05) and sarcopenia (unadjusted OR = 0.388, 95% CI: 0.230–0.652; adjusted OR range: 0.414–0.543, all P < 0.05). In patients with ILD, Low PA is independently associated with malnutrition and sarcopenia, and shows significant correlations with adverse body composition and functional decline.