Bioimpedance-Derived Phase Angle Was Associated with Faster Blood Pressure Stabilisation Following Orthostatic Challenge in Older Adults.

Phase Angle (PA), derived from bioelectrical impedance analysis, reflects cellular health and may indicate physiological resilience in ageing. We examined the relationship between PA and blood pressure (BP) recovery following an orthostatic challenge in 107 older adults attending a specialist falls clinic. Participants underwent active stand testing with continuous, beat-to-beat BP monitoring over 180 seconds. PA was categorised into tertiles (low, medium, high), and changes in systolic (SBP) and diastolic BP (DBP) were analysed using linear mixed-effects models, adjusted for age, sex, diabetes, hypertension, and cardiovascular and psychotropic medication use. Compared to the low PA tertile, individuals in the medium and high PA tertiles demonstrated faster recovery in both SBP and DBP during the 10-20 second post-stand period (all p < 0.001). No significant differences were observed in recovery between the 20-30 and 30-40 second intervals. Furthermore, participants in the high PA tertile showed, in contrast to the low PA tertile, full mean BP recovery at 40 seconds, with no further upward trend thereafter (p = 0.001 for SBP, p = 0.005 for DBP). PA could be a simple, non-invasive biomarker of dynamic physiological resilience, potentially identifying older adults at increased risk of early orthostatic haemodynamic instability.