Phase angle is related with inflammatory and oxidative stress biomarkers in older women

Background: The aim of this study was to examine the relation between phase angle (PhA) and inflammatory and oxidative stress biomarkers in older women. Methods: One hundred and fifty-five physically independent older women participated in this study (67.7 +/- 5.7 years, 27.0 +/- 4.4 kg/m(2)). Inflammatory markers included interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and acute phase reactive protein (CRP). Oxidative stress biomarkers comprised superoxide dismutase (SOD), catalase (CAT), advanced oxidation protein products (AOPP), and total radical-trapping antioxidant potential (TRAP). A spectral bioelectrical impedance device was used to estimate resistance (R) and reactance (Xc) at frequency 50 kHz, and subsequently PhA was calculated as arc-tangent (Xc / R) x 180 degrees / pi. The covariates appendicular lean soft-tissue (ALST), trunk fat mass, and total body fat were determined by whole-body dual-energy X-ray absorptiometry. Linear regression analysis was conducted to further test if PhA is related with the dependent variables, after adjusting for potential covariates. Results: After controlling for the potential covariates (age, trunk fat mass, ALST, and number of diseases) PhA exhibited a significant inverse relation with IL-6 (beta = -0.97; P < 0.01), TNF-alpha (beta = -0.84; P < 0.01), and CRP (beta = -0.58; P < 0.01). Conversely, PhA was significantly related to CAT (beta = 7.27; P < 0.01), SOD (beta = 10.55; P < 0.01) and TRAP (beta = 73.08; P < 0.01). The AOPP did not demonstrate a significant correlation with PhA (P > 0.05). Conclusion: Our findings show that PhA is a simple and relevant explanatory variable which is related inflammatory and stress oxidative markers in physically independent older women, regardless of age, number of diseases, and body composition.