Section 49
Chapter 48,837

Dual-energy x-ray absorptiometry-measured lean soft tissue mass: differing relation to body cell mass across the adult life span

St-Onge, M.-P.; Wang, J.; Shen, W.; Wang, Z.; Allison, D.B.; Heshka, S.; Pierson, R.N.; Heymsfield, S.B.

Journals of Gerontology. Series a Biological Sciences and Medical Sciences 59(8): 796-800


ISSN/ISBN: 1079-5006
PMID: 15345728
DOI: 10.1093/gerona/59.8.b796
Accession: 048836370

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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.

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