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Bioelectrical impedance analysis: population reference values for phase angle by age and sex
Maria Cristina G Barbosa-Silva1, Aluísio J D Barros, Jack Wang
1Programa de Pós-graduação em Epidemiologia, Universidade Federal de Pelotas, Brasil. cristinagbs@hotmail.com
The American Journal of Clinical Nutrition
|July 9, 2005
Summary
Phase angle, a bioelectrical impedance analysis indicator, varies significantly with sex, age, and body composition. These findings establish crucial reference values for clinical phase angle assessments.
Area of Science:
- Bioelectrical impedance analysis (BIA)
- Body composition assessment
- Physiological indicators
Background:
- Phase angle, derived from reactance and resistance via BIA, is a prognostic indicator with unclear biological significance.
- Establishing population-based reference values for phase angle is essential for its clinical application.
Purpose of the Study:
- To determine population average and standard deviation values for phase angle.
- To provide reference values for phase angle interpretation in clinical settings.
Main Methods:
- Conducted bioelectrical impedance analysis (BIA) and other body composition methods (hydrodensitometry, total body water) on 1967 healthy adults (18-94 years).
- Calculated phase angle directly from body resistance and reactance.
- Estimated fat mass (FM) using the Siri equation and compared phase angle across sex, age, BMI, and %FM categories.
Main Results:
- Phase angle was significantly lower in women than men (P < 0.001) and decreased with age (P < 0.001).
- Phase angle increased with higher BMI and was inversely associated with %FM in men.
- Sex, age, BMI, and %FM were significant predictors of phase angle in regression models.
Conclusions:
- Phase angle demonstrates significant variations based on sex, age, BMI, and body fat percentage.
- The derived reference values support the clinical utility of phase angle evaluations.