Author(s): SERAFINI, S., ORCAJADA, AM., VAQUERO-CRISTÓBAL R., ABRALDES JA., MARCOS-PARDO PJ., ESPARZA-ROS F., IZZICUPO P., Institution: UNIVERSITY , Country: ITALY, Abstract-ID: 1011

INTRODUCTION:
Aging is characterized by structural and functional decline, including reduced muscle quality, altered hydration, and impaired cellular integrity, increasing the risk of sarcopenia. Bioelectrical impedance vector analysis (BIVA) is a non-invasive approach for assessing tissue properties without predictive equations, while phase angle (PhA) is a derived bioelectrical parameter that may help identify older individuals at risk of frailty. The aim of this study was to investigate the relationship between functional parameters, sarcopenia categories, and BIVA patterns in older adults, and to establish sex- and age-specific reference values for BIVA and PhA.
METHODS:
This multicenter cross-sectional study included 449 Spanish older adults (322 females, F; 127 males, M; 74.1 ± 8.1 yrs). Body composition was assessed using phase-sensitive bioelectrical impedance (50 kHz), with resistance (R) and reactance (Xc) normalized for stature and plotted on the RXc graph according to the BIVA approach. Muscle function was evaluated by handgrip strength (HS), 5-times sit-to-stand (STS), and lower (LS) and upper (US) isometric strength. Participants were classified into five groups for age and sarcopenia categories according to the European Consensus [1]. Associations between PhA and functional parameters were examined using correlation analysis. Differences across age groups, functional tertiles, and sarcopenia categories were analyzed using univariate analyses, ANOVA, and multivariate vector comparisons, including Hotelling’s T² and Mahalanobis distance (D).
RESULTS:
Sex-specific BIVA tolerance ellipses (50%, 75%, 95%) and PhA percentiles by sex and age were generated. In both sexes, vectors shifted toward the lower-right quadrant with aging (F: D = 1.20–1.53 range, p < .001; M: D = 0.83–1.53 range, p ≤ .01). PhA decreased across age groups in both sexes (F: 5.66 ± 0.40° to 4.78 ± 0.65°, p < .001; M: 6.05 ± 0.82° to 5.05 ± 0.66°, p = .05) and showed significant correlations with HS, LS, and US (F: r = 0.28, r = 0.34; r = 0.25; M: r = 0.26, r = 0.44; r = 0.38, respectively; all p <.001). Significant differences in BIVA patterns were observed between the lowest and highest functional tertiles for HS, LS, and US (F: D = 0.53–1.14, D = 0.41–0.98, D = 0.46–1.13 ranges; M: D = 1.16–1.52, D = 0.71–1.78, D = 1.19–1.59 ranges, respectively; all p < .001). Significant differences were observed between non-sarcopenic and severe sarcopenia groups (F: D = 1.86–2.82 range; M: D = 2.70–3.00 range; all p < .001).
CONCLUSION:
BIVA and PhA effectively discriminate functional status and sarcopenia severity in older adults. Their association with muscle strength supports their role as indicators of tissue quality and functional impairment, providing clinically relevant reference values for early risk identification and targeted interventions. Reference: [1] Lopes NC, et al. (2025). doi: 10.1016/j.nut.2024.112654