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RELATIONSHIP BETWEEN SEGMENTAL AND WHOLE-BODY BIOELECTRICAL IMPEDANCE VARIABLES IN COMMUNITY-DWELLING OLDER ADULTS

Abstract

BACKGROUND: Previous research from the 20th century has shown reliability between the summation of segmental impedance (Z) compared to whole-body Z, particularly when electrodes are placed on the body’s right wrist, shoulder, hip, and ankle. However, modern BIA devices typically place electrodes on both hands and feet and forgo electrodes at the shoulder and hip. It is unknown if the evolution of BIA devices has affected relationships between segmental and whole-body Z, reactance (Xc), resistance (R), and phase angle (PhA). The purpose of this study was to compare both whole-body and segmental device-generated phase angle (PhADG) to phase angle calculated from left- and right-sided BIA values (PhACalc). We also compared BIA values between sides of the body. METHODS: We assessed PhA in 103 community-dwelling older women (n=87) and men (n=16) above 60 years of age with an InBody s10 BIA device at 50kHz. Participants sat with touch-type electrodes on their ankles, middle fingers, and thumbs. One male participant, an outlier with PhADG more than three standard deviations from the mean, was excluded from analysis. Left-sided Xc and PhACalc were nonnormal, thus nonparametric tests were used in comparisons for those values. Both right- and left-sided PhACalc were assessed for agreement with PhADG using a linear regression and Bland-Altman analysis. Segmental PhADG and PhACalc relationships were determined via Pearson’s or Kendall’s coefficients. Summed right- and left-sided BIA values were compared with a paired t-test or Wilcoxon rank. Data is presented as mean ± standard deviation, and alpha was set to p<0.05. RESULTS: PhADG (5.38±0.80°) demonstrated stronger agreement with right-sided PhACalc (bias=-0.04±0.05°, p=0.135, d=-0.149) compared to left-sided PhACalc (bias=0.137±0.15°, p=0.011, rrb=-0.290). Segmental BIA values (Z, R, PhA) differed between the left and right arms (p<0.05) but not between the legs. CONCLUSIONS: PhADG demonstrates strong agreement with right-sided PhACalc measurements in older adults. However, agreement was weaker between PhADG and left-sided PhACalc, suggesting greater variability in left-sided BIA variables that requires further investigation. Overall, the results align with previous research showing stronger relationships between whole-body and right-sided segmental impedance measures compared to the left side.

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