The bioimpedance phase angle may be associated with frailty in rheumatoid arthritis patients: Results from a prospective, cohort study

Objectives This study investigated whether the phase angle (PhA) on bioelectrical impedance analysis is related to frailty in rheumatoid arthritis (RA) patients. Methods Data from a prospective cohort study of RA patients were analysed. The PhA was assessed by the bioelectrical impedance analysis method, and frailty was assessed by the Kihon Check List (KCL) annually. The cut-off value of the PhA for frailty was calculated by receiver-operating characteristic analysis. The relationships between the PhA and frailty were evaluated by logistic regression analysis. The relationships between the change in PhA and frailty status and the KCL score were evaluated by analysis of covariance and multiple regression analysis. Results A total of 170 patients (81.2% female, 66.2 +/- 13.1 years) were included in the analysis. A PhA of less than the cut-off for frailty was significantly associated with frailty (odds ratio: 4.75, 95% confidence interval: 1.86, 12.17). The change in the PhA was significantly associated with the change in the KCL score (beta = -0.15). In robust patients, there was a significant difference in the rate of change of the PhA between the group that became pre-frail in the next year and the group that remained robust. Conclusions The PhA may be associated with frailty in RA patients.