Phase angle is related to physical function in high-risk Dutch older adults: implications for sarcopenia screening.

Introduction: Sarcopenia, a progressive age-related loss of skeletal muscle mass and function, poses significant health risks in older adults. Phase angle (PhA), derived from bioimpedance analysis, has been proposed as an indicator of muscle quality and physical functioning. This study investigates the association between PhA and physical function, and its potential utility in case-finding phase of sarcopenia assessment based on EWGSOP2 functional cut-offs.

Methods: This cross-sectional observational study used baseline data from two clinical trials involving Dutch older adults (≥65 years, n=228) at risk of malnutrition or frailty. PhA was measured using multi-frequency bioimpedance vector analysis. Physical functioning was assessed through handgrip strength, knee extension strength, chair rise test, and gait speed (4m and 400-m/6-min walk tests). Associations were evaluated using linear mixed models adjusted for age, gender, height, and lean body mass. Receiver-operating characteristic (ROC) analyses identified PhA thresholds for low performance based on EWGSOP2 cut-offs.

Results: PhA was significantly associated with all performance outcomes in crude models. After adjustment, each unit increase in PhA was associated with a 43.5 ± 8.4 N increase in knee extension strength (P < 0.0001), a 1.5 ± 0.4 s reduction in chair rise time (P = 0.0004), and a 0.14 ± 0.02 m/s increase in gait speed (P < 0.0001). Associations with handgrip strength became non-significant after full adjustment. A PhA threshold of 5.4° showed high sensitivity (0.96) for detecting low physical performance via the chair rise test. However, misclassification rates exceeded 25 %.

Conclusions: PhA is associated with physical function, particularly lower-body performance measures, but without muscle mass assessment, it cannot support a complete diagnosis of sarcopenia. It may be valuable as a case-finding tool in older adults at risk.