Dual-energy x-ray absorptiometry-measured lean soft tissue mass: differing relation to body cell mass across the adult life span.
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.
St-Onge
Marie-Pierre
MP
St. Luke's-Roosevelt Hospital, Columbia University College of Physicians and Surgeons, New York, NY, USA.
Wang
Jack
J
Shen
Wei
W
Wang
ZiMian
Z
Allison
David B
DB
Heshka
Stanley
S
Pierson
Richard N
RN
Heymsfield
Steven B
SB
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