Abstract
BACKGROUND: Frailty is a multidimensional phenotype that describes declining physical function and a vulnerability to adverse outcomes in the setting of physical stress such as illness or hospitalization. Phase angle is a composite measure of tissue resistance and reactance measured via bioelectrical impedance analysis (BIA). Whether phase angle is associated with frailty and mortality in the general population is unknown. OBJECTIVE: To evaluate associations among phase angle, frailty and mortality. DESIGN: Population-based survey. SETTING: Third National Health and Nutritional Examination Survey (1988-1994). PARTICIPANTS: In all, 4,667 persons aged 60 and older. MEASUREMENTS: Frailty was defined according to a set of criteria derived from a definition previously described and validated. RESULTS: Narrow phase angle (the lowest quintile) was associated with a four-fold higher odds of frailty among women and a three-fold higher odds of frailty among men, adjusted for age, sex, race-ethnicity and comorbidity. Over a 12-year follow-up period, the adjusted relative hazard for mortality associated with narrow phase angle was 2.4 (95 % confidence interval [95 % CI] 1.8 to 3.1) in women and 2.2 (95 % CI 1.7 to 2.9) in men. Narrow phase angle was significantly associated with mortality even among participants with little or no comorbidity. LIMITATIONS: Analyses of BIA and frailty were cross-sectional; BIA was not measured serially and incident frailty during follow-up was not assessed. Participants examined at home were excluded from analysis because they did not undergo BIA. CONCLUSIONS: Narrow phase angle is associated with frailty and mortality independent of age and comorbidity.