title: Associations between body composition and bone density and structure in men and women across the adult age spectrum.
abstract: OBJECTIVE
  The objective of this study was to identify independent associations between body composition and bone outcomes, including cortical structure and cortical and trabecular volumetric bone mineral density (vBMD) across the adult age spectrum.
  
  
  METHODS
  This cross-sectional study evaluated over 400 healthy adults (48% male, 44% black race), ages 21-78years. Multivariable linear regression models evaluated associations between whole-body DXA measures of lean body mass index (LBMI) and fat mass index (FMI) and tibia peripheral quantitative CT (pQCT) measures of cortical section modulus, cortical and trabecular vBMD and muscle density (as a measure of intramuscular fat), adjusted for age, sex, and race. All associations reported below were statistically significant (p<0.05).
  
  
  RESULTS
  Older age and female sex were associated with lower LBMI and muscle strength. Black race was associated with greater LBMI but lower muscle density. Greater FMI was associated with lower muscle density. Cortical section modulus was positively associated with LBMI and muscle strength and negatively associated with FMI. Adjustment for body composition eliminated the greater section modulus observed in black participants and attenuated the lower section modulus in females. Greater LBMI was associated with lower cortical BMD and greater trabecular BMD. FMI was not associated with either BMD outcome. Greater muscle density was associated with greater trabecular and cortical BMD. Associations between body composition and bone outcomes did not vary by sex (no significant tests for interaction).
  
  
  CONCLUSIONS
  These data highlight age-, sex- and race-specific differences in body composition, muscle strength and muscle density, and demonstrate discrete associations with bone density and structure. These data also show that age-, sex- and race-related patterns of bone density and strength are independent of differences in body composition. Longitudinal studies are needed to examine the temporal relations between changes in bone and body composition.
authors.affiliation: Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. bakerjo@uphs.upenn.edu
authors.forename: Joshua F
authors.initials: JF
authors.lastname: Baker
authors.forename: Matthew
authors.initials: M
authors.lastname: Davis
authors.forename: Ruben
authors.initials: R
authors.lastname: Alexander
authors.forename: Babette S
authors.initials: BS
authors.lastname: Zemel
authors.forename: Sogol
authors.initials: S
authors.lastname: Mostoufi-Moab
authors.forename: Justine
authors.initials: J
authors.lastname: Shults
authors.forename: Michael
authors.initials: M
authors.lastname: Sulik
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Schiferl
authors.forename: Mary B
authors.initials: MB
authors.lastname: Leonard
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001823:Body Composition; D015992:Body Mass Index; D015519:Bone Density; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D014057:Tomography, X-Ray Computed; D055815:Young Adult