Increased Phase Angle Reflects Improvement in Activities of Daily Living and Muscle Health in Post-stroke Rehabilitation

BACKGROUND: Phase angle (PhA) reflects cellular integrity and muscle quality. However, evidence is limited regarding whether an increase in PhA is associated with improvements in activities of daily living (ADL) and skeletal muscle mass. This study aimed to investigate the association between change in PhA and prognosis in terms of ADL and skeletal muscle mass in post-stroke patients undergoing rehabilitation. METHODS: This retrospective cohort study was conducted at a convalescent rehabilitation hospital in Japan. Patients with a PhA at admission below the cutoff values (4.76° for male and 4.11° for female) were included. Patients were categorized into a PhA-increase group (>0) and a non-increase group (≤0). Outcomes included the Functional Independence Measure (FIM)-motor score and skeletal muscle mass index (SMI) at discharge. Multivariate regression was used to assess associations. RESULTS: A total of 253 patients were included (mean age 78.0±10.9 years; 51% females). The median PhA at admission was 3.70° (interquartile range [IQR], 3.20-4.10), and the median change during hospitalization was 0.00° (IQR, -0.20- 0.30). Of these, 119 patients had increased PhA and 134 did not. Change in PhA was independently associated with higher FIM-motor scores (β=0.078, p=0.040) and greater SMI (β=0.454, p<0.001) at discharge. CONCLUSIONS: In post-stroke patients, an increase in PhA during hospitalization was associated with better functional and muscular outcomes. PhA may therefore serve as a valuable biomarker for assessing the efficacy of rehabilitation.