Phase angle as an estimator of daily step count in older adults: A cross-sectional study
Keisuke Nakamura, Yuya Nagasawa, Tomohiro Sasaki, Masayuki ShimizuABSTRACT
Background:
Daily step count is a simple and informative physical activity (PA) measure in older adults; however, it is often unavailable in clinical settings. Phase angle (PhA), derived from bioelectrical impedance analysis (BIA), could serve as a surrogate muscle quality and habitual activity marker.
Objectives:
We aimed to examine whether PhA could estimate step count and identify individuals meeting clinically relevant PA thresholds.
Methods:
In this cross-sectional study, we involved 150 community-dwelling adults (age: ≥60 years) from a frailty outpatient clinic, recording their daily step count over 7 days using a pedometer and measuring their PhA via multi-frequency BIA. Using multiple linear regression, we tested the association between PhA and step count, adjusting for age. Our receiver operating characteristic (ROC) analyses evaluated the potential of PhA to discriminate step thresholds (i.e., ≥2000, 4000, 6000, and 8000 steps/day), stratified by sex and age (i.e., <80 vs. ≥80 years).
Results:
PhA was significantly associated with step count (β = 2071.6,
Conclusion:
PhA was significantly associated with daily step count and effectively identified older adults with higher activity levels, particularly males and those aged ≥80 years. PhA might thus serve as a practical proxy for PA when direct measurement is not feasible.