Association Between Phase Angle and AWGS 2025-Defined Sarcopenia in Community-Dwelling Older Adults

Background/Objectives: Phase angle (PhA), derived from bioelectrical impedance analysis (BIA), has been proposed as an indicator of cellular health, nutritional status, and physical function. This study aimed to investigate the association between PhA, physical function, and sarcopenia defined according to the Asian Working Group for Sarcopenia (AWGS) 2025 criteria in community-dwelling older adults. In addition, we explored a preliminary PhA cutoff for discriminating women with prevalent sarcopenia. Methods: This cross-sectional study included 317 participants (81 men, 236 women) aged ≥65 years who participated in functional assessments conducted in three locations of Fukushima Prefecture, Japan, in 2024. PhA at 50 kHz was measured using BIA. Assessments included body composition, grip strength, knee extension strength, maximum walking speed, Timed Up and Go (TUG), the Montreal Cognitive Assessment, Japanese version (MoCA-J), and the Kihon Checklist (KCL). Sarcopenia was defined according to the AWGS 2025 criteria. Group differences were examined using the Mann–Whitney U test, and associations were assessed using Spearman’s rank correlation coefficients. Age-adjusted logistic regression analysis was performed in women to examine the association between PhA and sarcopenia. Receiver operating characteristic (ROC) analysis was performed in women to explore a preliminary PhA cutoff because the limited number of men with sarcopenia precluded a stable sex-specific analysis. Results: Sex-specific Spearman’s rank correlation analyses showed that lower PhA values were associated with lower muscle strength (grip strength and knee extension strength) and poorer physical function (maximum walking speed and Timed Up and Go [TUG] performance) in both men and women. Lower PhA values were independently associated with prevalent sarcopenia in women after adjustment for age (odds ratio, 0.26; 95% CI, 0.09–0.80). ROC analysis identified an exploratory PhA cutoff of 4.48° for discriminating women with prevalent sarcopenia (AUC = 0.67; sensitivity = 0.65; specificity = 0.71), indicating modest discriminative performance. Conclusions: Lower PhA values were cross-sectionally associated with poorer physical function and prevalent sarcopenia among community-dwelling older women. An exploratory PhA cutoff of 4.48° was identified to discriminate prevalent sarcopenia in women. However, this cutoff should be considered hypothesis-generating rather than an established clinical threshold and requires validation in larger, independent cohorts and prospective longitudinal studies before clinical application.