Clinical Significance of Phase Angle for Assessing Quality of Life and Prognosis in Hemodialysis Patients

<b>Background/Objectives:</b> The phase angle (PA), derived from bioelectrical impedance analysis (BIA), reflects cellular integrity and nutritional status. Previous studies have reported associations between PA, QOL, and prognosis in hemodialysis patients; however, evidence in Japanese populations remains limited. This multicenter study aimed to confirm and extend these associations by examining the relationships of PA with QOL domains and survival outcomes in maintenance HD patients. <b>Methods:</b> In this multicenter cross-sectional study, 319 HD patients were stratified into sex-specific PA quartiles, and baseline characteristics, laboratory data, and body composition measures were compared across groups. Health-related QOL was assessed using the SF-36 and KDQOL-SF™. Associations between PA and QOL were tested with multivariable linear regression models. Survival was evaluated using Kaplan-Meier analysis with Bonferroni-adjusted pairwise comparisons. <b>Results:</b> Higher PA was significantly associated with favorable nutritional and laboratory parameters, including higher hemoglobin, albumin, creatinine, and GNRI, and lower NT-proBNP. PA also correlated positively with muscle mass and intracellular water, and inversely with the ECW/ICW ratio. Multivariable analyses showed that PA remained independently associated with several physical QOL domains, including physical functioning, role-physical, and general health, even after adjustment for dialysis adequacy (Kt/V) and inflammation (CRP). Kaplan-Meier analysis demonstrated lower survival in the lowest PA quartile, and ROC analysis identified sex-specific cutoff values for predicting mortality (4.0° for females, 4.8° for males). <b>Conclusions:</b> This multicenter confirmatory study showed that PA is independently associated with nutritional status, physical QOL, and mortality in maintenance hemodialysis patients. PA may serve as a practical, noninvasive biomarker for nutritional and functional assessment in clinical practice.