Examining Device-Generated And Calculated Bioelectrical Impedance Analysis Variables In Community-Dwelling Older Adults

PURPOSE: Previous research has shown a strong agreement between the sum of segmental impedance (Z) and total body Z, particularly when electrodes are placed on the right wrist, shoulder, hip, and ankle of the body. However, modern bioelectrical impedance analysis (BIA) devices typically forgo shoulder and hip electrodes, which may affect whole-body measurements. With BIA emerging as a clinical tool for assessing older adults, it remains necessary to determine the relationship between the whole body and segmental Z, reactance (Xc), resistance (R), and phase angle (PhA) using modern BIA devices that place electrodes on both sides of the body. The purpose of this investigation was to compare both whole-body and segmental device-generated phase angle (PhADG) with the phase angle calculated from the left, right, and combined sides of the body (PhACalc), and to compare bioelectric variables between sides of the body. METHODS: A sample of 103 community-dwelling older adults were assessed using a 50 kHz direct segmental multifrequency BIA device. Whole-body PhACalc values were assessed for agreement with PhADG using 2.5th and 97.5th quantile limits of agreement and Kendall’s tau. Bioelectrical values between sides of the body were also compared using Wilcoxon rank and Kendall’s tau. RESULTS: A smaller mean difference was observed between PhADG and right PhACalc (-0.004°, p = 0.256) than between PhACalc on the left (0.107°, p = 0.01) and on the combined sides (0.107°, p < 0.001). The sum of Z, R and PhACalc was significantly different (p < 0.01) between the left (559.66 ± 99.55Ω, 556.80 ± 99.52Ω, 5.51 ± 1.5°, respectively) and the right sides (554.60 ± 94.52Ω, 552.02 ± 94.23Ω, 5.41 ± 0.8°, respectively). CONCLUSIONS: Bilateral BIA values are not interchangeable when determining whole-body measurements. Present data suggests that the right side would be the most appropriate choice for measuring whole-body bioelectrical variables. This study was supported by National Institutes of Health Grants #R01MD018025 and #R03AG06799.