title: Dual energy X-ray absorptiometry body composition and aging in a population-based older cohort.
abstract: OBJECTIVE
  The aims of this cross-sectional study were (1) to examine the effect of age on body composition in older adults using dual-energy X-ray absorptiometry (DXA) and (2) to evaluate the agreement of DXA with standard indirect anthropometric measures (body mass index (BMI), waist circumference and waist-to-hip ratio (WHR)).
  
  
  METHODS
  A population-based sample of 731 adults aged between 50 and 79 years underwent measurement of BMI, waist circumference, WHR, DXA total body fat mass, DXA % total body fat, DXA % trunk fat and DXA lean body mass. Linear regression was used to test for trend in measures of body composition between age categories in men and women. Partial correlations and Bland-Altman analysis were used to examine the agreement of DXA measures with indirect measures.
  
  
  RESULTS
  DXA lean body mass decreased significantly with increasing age in both sexes (P<0.05). In males, BMI (P=0.01) and body weight (P<0.01) decreased with age, and in females, WHR (P=0.05), DXA % total fat (P=0.02) and DXA % trunk fat (P=0.05) increased with age. There was good agreement between DXA measures of fatness and indirect anthropometric measures, except for WHR, which showed greater variability in its comparisons with DXA.
  
  
  CONCLUSIONS
  Using the highly sensitive and direct DXA method of measuring body composition, a decline in lean body mass and an increase in adiposity was observed with aging. Except for WHR, indirect anthropometric measures generally showed high levels of agreement with DXA fat measures in this older cohort.
authors.affiliation: Menzies Research Institute, University of Tasmania, Hobart, Tasmania, Australia. kelly.shaw@dhhs.tas.gov.au
authors.forename: K A
authors.initials: KA
authors.lastname: Shaw
authors.forename: V K
authors.initials: VK
authors.lastname: Srikanth
authors.forename: J L
authors.initials: JL
authors.lastname: Fryer
authors.forename: L
authors.initials: L
authors.lastname: Blizzard
authors.forename: T
authors.initials: T
authors.lastname: Dwyer
authors.forename: A J
authors.initials: AJ
authors.lastname: Venn
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000502:physiology; D000368:Aged; D000375:Aging / Q000502:physiology*; D000886:Anthropometry / Q000379:methods; D001823:Body Composition / Q000502:physiology*; D001824:Body Constitution / Q000502:physiology; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results