Association of bioimpedance‐derived 50‐kHz phase angle as marker of body composition with electrical parameters regarding the Cole‐Cole model

Our aim is to clarify the association of the bioelectrical impedance‐derived 50‐kHz phase angle (φ 50 ) with electrical parameters regarding the Cole‐Cole model and clinical parameters. A total of 440 sets of bioelectrical impedance data from pre‐ and post‐hemodialysis from 157 patients were used. Resistance at infinite frequency ( R inf ), resistance at 0 frequency ( R 0 ), capacitance of the cell membrane (Cm), and a parameter for the distribution of the time constant ( α ) were examined as electrical parameters. Normally hydrated lean tissue mass as a percentage of the dry weight ( P NHLT ), excess fluid mass as a percentage of the dry weight ( P ExF ), body mass index (BMI), age, and sex (N sex , 0 for male, 1 for female) were examined as clinical parameters. φ 50 increased with the decrease in R inf / R 0 and α and also with the increase in Cm (multiple regression coefficients [ β ]: pre/post, −0.886/−0.936, −0.175/−0.212, and 0.167/0.141), which determined the ratio of intra‐ to extracellular fluid volume (ICV/ECV), tissue homogeneity, and total cell mass. φ 50 increased with an increase in P NHLT and BMI and decrease in P ExF , N sex , and age (β: pre/post, 0.654/0.581, 0.466/0.412, −0.483/−0.473, −0.216/−0.154, and −0.145/−0.127). The concordance correlation coefficient between φ 50 for pre‐ and post‐hemodialysis ( ρ = 0.772) may be improved ( ρ = 0.950) by adding a multiplication of 0.2 and P ExF to φ 50 for correction. φ 50 may be used to estimate body composition through the association with ICV/ECV, tissue homogeneity, and total cell mass. The correction for excess fluid is essential in order to use φ 50 as a marker of body composition related to nutrition.