title: Dual-energy x-ray absorptiometry-measured lean soft tissue mass: differing relation to body cell mass across the adult life span.
abstract: Lean soft tissue (LST) measured by dual-energy X-ray absorptiometry (DEXA) is used as a metabolic measure in aging research despite evidence of extracellular fluid expansion and a corresponding reduction in body cell mass (BCM) in older participants. We investigated the hypothesis that the fraction of LST as BCM is smaller with greater age. Men and women (n = 2043) had DEXA and 40K-counting for body potassium and BCM measured on the same day. Both BCM and LST were lower with greater age but the relative lowering was larger for BCM. A multiple linear regression model was fitted with BCM/LST as the dependent variable, and age, sex, and interaction terms as independent variables. Men had a mean BCM/LST greater (p < .001) than women; quadratic and cubic age terms were also significant or approached significance. Thus, the fraction of LST as BCM is smaller in older adults, a finding that has implications for the interpretation of DEXA results.
authors.affiliation: St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, New York, NY, USA.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: St-Onge
authors.forename: Jack
authors.initials: J
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.forename: ZiMian
authors.initials: Z
authors.lastname: Wang
authors.forename: David B
authors.initials: DB
authors.lastname: Allison
authors.forename: Stanley
authors.initials: S
authors.lastname: Heshka
authors.forename: Richard N
authors.initials: RN
authors.lastname: Pierson
authors.forename: Steven B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged