title: Body composition in the elderly: reference values and bioelectrical impedance spectroscopy to predict total body skeletal muscle mass.
abstract: OBJECTIVE
  To validate the bioelectrical impedance spectroscopy (BIS) model against dual-energy X-ray absorptiometry (DXA), to develop and compare BIS estimates of skeletal muscle mass (SMM) to other prediction equations, and to report BIS reference values of body composition in a population-based sample of 75-year-old Swedes.
  
  
  METHODS
  Body composition was measured by BIS in 574 subjects, and by DXA and BIS in a subset of 98 subjects. Data from the latter group was used to develop BIS prediction equations for total body skeletal muscle mass (TBSMM).
  
  
  RESULTS
  Average fat free mass (FFM) measured by DXA and BIS was comparable. FFM(BIS) for women and men was 40.6 kg and 55.8 kg, respectively. Average fat free mass index (FFMI) and body fat index (BFI) for women were 15.6 and 11.0. Average FFMI and BFI for men were 18.3 and 8.6. Existing bioelectrical impedance analysis equations to predict SMM were not valid in this cohort. A TBSMM prediction equation developed from this sample had an R(2)(pred) of 0.91, indicating that the equation would explain 91% of the variability in future observations.
  
  
  CONCLUSIONS
  BIS correctly estimated average FFM in healthy elderly Swedes. For prediction of TBSMM, a population specific equation was required.
authors.affiliation: Department of Clinical Nutrition, Sahlgrenska University Hospital, Sahlgrenska Academy at University of Gothenburg, Goteborg, Sweden.
authors.forename: Marja
authors.initials: M
authors.lastname: Tengvall
authors.forename: Lars
authors.initials: L
authors.lastname: Ellegård
authors.forename: Vibeke
authors.initials: V
authors.lastname: Malmros
authors.forename: Niklas
authors.initials: N
authors.lastname: Bosaeus
authors.forename: Lauren
authors.initials: L
authors.lastname: Lissner
authors.forename: Ingvar
authors.initials: I
authors.lastname: Bosaeus
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods / Q000592:standards; D000273:Adipose Tissue / Q000378:metabolism*; D000368:Aged; D000375:Aging; D000465:Algorithms; D001823:Body Composition / Q000502:physiology*; D001834:Body Water / Q000378:metabolism; D015331:Cohort Studies; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D011237:Predictive Value of Tests; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013548:Sweden