Baseline phase angle is associated with morphofunctional status, length of stay, and hospitalization costs in severe anorexia nervosa: the EDIGRA study.

内容摘要

Phase angle (PhA), derived from bioelectrical impedance analysis, reflects bioelectrical properties related to cellular mass and fluid distribution and has been proposed as a marker of malnutrition severity. However, its exploratory association with morphofunctional status and hospitalization-related outcomes in severe anorexia nervosa (AN) remains insufficiently characterized. This study aimed to explore whether baseline PhA is associated with morphofunctional status, length of stay, and inpatient costs in a specialized eating disorders unit. In this prospective cohort study, 42 female inpatients with severe AN or other specified feeding and eating disorder were assessed at admission. Patients were stratified into tertiles according to PhA. Anthropometry, body composition by bioelectrical impedance vector analysis (BIVA), intracellular and extracellular water distribution, handgrip strength, muscle and abdominal ultrasound parameters, biochemical markers, and length of stay were recorded. Hospitalization costs were estimated using standardized diagnosis-related group daily expenditure. Mean PhA values were 4.0°, 4.7°, and 5.5° in the low, mid, and high tertiles, respectively. Importantly, total body weight did not differ significantly across tertiles. In contrast, body cell mass index increased progressively (5.2, 6.1, and 6.9 kg/m²). Higher PhA was associated with greater rectus femoris cross-sectional area (2.3 vs. 3.7 cm²) and higher handgrip strength (20.3 vs. 24.9 kg), consistent with more favorable muscle structure and function in unadjusted comparisons. Hydration profiles also differed: extracellular water proportion decreased (52.7% to 40.3%), while intracellular water increased (44.1% to 53.3%) across tertiles. Median length of stay declined from 58.4 to 41.3 days, with corresponding reductions in estimated hospitalization costs (€36,523 to €25,829), which should be interpreted descriptively because cost estimates were largely driven by hospitalization duration. ROC analysis showed modest discriminatory performance for prolonged hospitalization (AUC = 0.65; exploratory threshold: 4.5-4.6°). Baseline PhA was associated with differences in morphofunctional profiles and hospitalization trajectories despite similar body weight, suggesting that it may capture morphofunctional variability not reflected by anthropometry alone. Its associations with cellular mass, hydration distribution, muscle function, and length of stay suggest that PhA may provide complementary descriptive information within a broader clinical assessment. However, given the modest discriminative performance, sample size, and lack of multivariable adjustment, PhA should not be considered a standalone prognostic tool. Larger multicenter studies are needed to validate thresholds and formally test whether PhA provides incremental information beyond conventional anthropometric, clinical, psychological, and organizational factors. Approved by the Provincial Research Ethics Committee of Granada (SICEIA-2024-003069). People with severe anorexia nervosa often need hospital treatment to restore their physical health safely. Healthcare professionals usually monitor recovery using body weight and body mass index (BMI), but these measures do not always reflect how well the body’s tissues, muscles, and cells are functioning. This study examined whether a measurement called phase angle could provide additional and more detailed information about the physical condition of the body. Phase angle is obtained from a painless body composition test that uses a very small electrical current. It gives information about cell mass, muscle condition, and body fluid balance. In particular, it reflects differences between water inside the cells and water outside the cells, which may be altered in severe malnutrition. Higher phase angle values are generally associated with more favorable cellular and muscle health. We studied 42 women admitted to hospital with severe anorexia nervosa or other specified feeding and eating disorder. Although patients had similar body weight, those with higher phase angle values showed stronger muscles, more favorable tissue-related measurements, and better body fluid balance at admission. They also had shorter hospital stays and lower treatment costs, although these lower costs were largely explained by shorter hospital stays. In contrast, patients with lower phase angle values tended to require longer inpatient care. These findings suggest that phase angle may help healthcare teams better understand the physical condition of patients beyond weight alone. Including phase angle in routine assessment may provide complementary information for clinical monitoring, but it should be used alongside broader medical, psychological, and organizational assessment during hospital treatment for anorexia nervosa, rather than as a standalone tool for predicting recovery, hospital stay, or discharge timing.