Bioelectrical impedance analysis: population reference values for phase angle by age and sex.
BACKGROUND
Phase angle is an indicator based on reactance and resistance obtained from bioelectrical impedance analysis (BIA). Although its biological meaning is still not clear, phase angle appears to have an important prognostic role.


OBJECTIVE
The aim of this study was to estimate population averages and SDs of phase angle that can be used as reference values.


METHODS
BIA and other methods used to evaluate body composition, including hydrodensitometry and total body water, were completed in 1967 healthy adults aged 18-94 y. Phase angle was calculated directly from body resistance and reactance, and fat mass (FM) was estimated from the combination of weight, hydrodensitometry, and total body water by using the 3-compartment Siri equation. Phase angle values were compared across categories of sex, age, body mass index (BMI), and percentage FM.


RESULTS
Phase angle was significantly (P < 0.001) smaller in women than in men and was lower with greater age (P < 0.001). Phase angle increased with an increase in BMI and was significantly inversely associated with percentage fat in men. Phase angle was significantly predicted from sex, age, BMI, and percentage FM in multiple regression models.


CONCLUSIONS
Phase angle differs across categories of sex, age, BMI, and percentage fat. These reference values can serve as a basis for phase angle evaluations in the clinical setting.
Programa de Pós-graduação em Epidemiologia, Universidade Federal de Pelotas, Brasil. cristinagbs@hotmail.com
Maria Cristina G
MC
Barbosa-Silva
Aluísio J D
AJ
Barros
Jack
J
Wang
Steven B
SB
Heymsfield
Richard N
RN
Pierson
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001823:Body Composition; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status; D012016:Reference Values; D012737:Sex Factors