title: Pediatric reference data for lean tissue properties: density and hydration from age 5 to 20 y.
abstract: BACKGROUND
  Hydrometry and densitometry are widely used to assess pediatric body composition due to their ease of application. The accuracy of these techniques depends on the validity of age- and sex-specific constant values for lean tissue hydration or density. Empirical data on these constants, and their variability between individuals, are lacking.
  
  
  OBJECTIVE
  The objectives were to measure lean tissue hydration and density in a large sample of children and adolescents and to derive prediction equations.
  
  
  METHODS
  Body composition was measured in 533 healthy individuals (91% white) aged 4-23 y by using the 4-component model. Age- and sex-specific median values for hydration and density were obtained by using the LMS (lambda, mu, sigma) method. Regression analysis was used to generate prediction equations on the basis of age, sex, and body mass index SD score (BMI SDS). Values were compared with those in previously published predictions.
  
  
  RESULTS
  Age-associated changes in density and hydration differed between the sexes. Compared with our empirical values, use of published values resulted in a mean bias of 2.1% fat (P < 0.0001). Age, sex, and BMI SDS were all significant predictors of lean tissue hydration and density. With adjustment for age and sex, hydration was higher, and density lower, in higher-BMI SDS individuals.
  
  
  CONCLUSIONS
  The chemical maturation of lean tissue is not a linear process and proceeds differently in males and females. Previously published reference values are inaccurate and induce clinically significant bias in percentage fat. New empirical reference values are provided for use in pediatric hydrometry and densitometry. Further research that extends to cover nonwhite ethnic groups is needed.
authors.affiliation: Institute of Child Health, London, UK. j.wells@ich.ucl.ac.uk
authors.forename: Jonathan C K
authors.initials: JC
authors.lastname: Wells
authors.forename: Jane E
authors.initials: JE
authors.lastname: Williams
authors.forename: Sirinuch
authors.initials: S
authors.lastname: Chomtho
authors.forename: Tegan
authors.initials: T
authors.lastname: Darch
authors.forename: Carlos
authors.initials: C
authors.lastname: Grijalva-Eternod
authors.forename: Kathy
authors.initials: K
authors.lastname: Kennedy
authors.forename: Dalia
authors.initials: D
authors.lastname: Haroun
authors.forename: Catherine
authors.initials: C
authors.lastname: Wilson
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Cole
authors.forename: Mary S
authors.initials: MS
authors.lastname: Fewtrell
mesh_terms: D000273:Adipose Tissue; D000293:Adolescent; D000367:Age Factors; D001823:Body Composition; D001825:Body Fluid Compartments / Q000502:physiology*; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003720:Densitometry / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D009765:Obesity / Q000473:pathology; D015995:Prevalence; D012016:Reference Values; D012737:Sex Factors; D014867:Water / Q000032:analysis*; D055815:Young Adult
chemical_list: D014867:Water