title: Phase angle from bioelectrical impedance analysis: population reference values by age, sex, and body mass index.
abstract: BACKGROUND
  The use of bioelectrical impedance phase angle has been recommended as a prognostic tool in the clinical setting, but published reference data bases are discrepant and incomplete (eg, they do not consider body mass index [BMI], and data are lacking for children).
  
  
  METHODS
  Phase angle reference values stratified by age, sex, and BMI were generated in a large German data base of 15,605 children and adolescents and 214,732 adults, and the determinants of phase angle values were assessed. The reference values were applied to 3 groups of patients and compared with previously published reference values from the United States and Switzerland.
  
  
  RESULTS
  Gender and age were the main determinants of phase angle in adults, with men and younger subjects having higher phase angles. In children and adolescents, age and BMI were the main determinants of phase angle. In normal and overweight adults, phase angle increased with increasing BMI, but there was an inverse association at a BMI >40 kg/m2. In cirrhosis, the prevalence of a low phase angle increased with the state of disease, whereas it was not different between patients with the metabolic syndrome and controls. There are considerable differences between phase angle reference values from different populations. These differences are not explained by age or BMI and may be due to differences between impedance analyzers.
  
  
  CONCLUSIONS
  The determinants of phase angle differ between adults and children. In adults, the influence of BMI on phase angle depended on the BMI range. The prognostic value of phase angle may differ in different clinical settings. The use of population-specific and probably impedance-analyzer-specific reference values for phase angle is recommended.
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts-University Kiel, Kiel, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Bosy-Westphal
authors.forename: Sandra
authors.initials: S
authors.lastname: Danielzik
authors.forename: Ralf-Peter
authors.initials: RP
authors.lastname: Dörhöfer
authors.forename: Wiebke
authors.initials: W
authors.lastname: Later
authors.forename: Sonja
authors.initials: S
authors.lastname: Wiese
authors.forename: Manfred J
authors.initials: MJ
authors.lastname: Müller
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D002648:Child; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status; D011237:Predictive Value of Tests; D012016:Reference Values; D012737:Sex Factors