Segmental Bioimpedance Phase Angles for Frailty Detection in Hospitalized Older Adults with Cardiovascular Disease: A Cross-Sectional Observational Study

Background/Objectives: Whole-body phase angle is associated with in-hospital morbidity and mortality, although cut-off points vary. Studies on the relationship between segmental phase angles and frailty in patients with cardiovascular disease are limited. Therefore, we aimed to assess the prognostic value of segmental phase angles in detecting frailty in older adults hospitalized with cardiovascular disease. Methods: A cross-sectional observational study was conducted on hospitalized patients aged ≥60 years with cardiovascular disease (sample size: 117–158 subjects). Frailty was identified using Fried’s five criteria. Biomarkers, body composition, and segmental phase angles were assessed using multifrequency bioimpedance. Associations with frailty were analyzed using logistic regression and Receiver Operating Characteristic (ROC) curves. Sensitivity, specificity, and positive likelihood ratio (LR+) were calculated (95% CI; p < 0.05). Results: A total of 157 patients (men: 64.24%; women: 33.76%) were included, with a mean age of 73.23 years (SD = 7.91). The prevalence of frailty was 28.66%. In men, the phase angles of the left hemisphere (5.15°) and left leg (4.25°) demonstrated moderate-accuracy capacity (AUC: 0.66–0.71; LR+: >2). In women, the segments with significance did not exceed an LR+ of 2. Frailty was associated with lower phase angle values in all segments and biomarkers such as hemoglobin < 12 g/dL (p = 0.011) and CRP > 5 mg/L (p = 0.030). Conclusions: Segmental phase angles demonstrated moderate discriminatory capacity for identifying frailty among hospitalized older men with cardiovascular disease, though predictive capacity in women was limited. This approach may support bedside frailty screening and inform individualized management.