title: A longitudinal analysis of sex differences in bone mineral accrual in healthy 8-19-year-old boys and girls.
abstract: BACKGROUND
  Although early in life there is little discernible difference in bone mass between boys and girls, at puberty sex differences are observed. It is uncertain if these differences represent differences in bone mass or just differences in anthropometric dimensions.
  
  
  OBJECTIVE
  The study aimed to identify whether sex independently affects bone mineral content (BMC) accrual in growing boys and girls. Three sites are investigated: total body (TB), femoral neck (FN) and lumbar spine (LS).
  
  
  METHODS
  85 boys and 67 girls were assessed annually for seven consecutive years. BMC was assessed by dual energy X-ray absorptiometry (DXA). Biological age was defined as years from age at peak height velocity (PHV). Data were analysed using a hierarchical (random effects) modelling approach.
  
  
  RESULTS
  When biological age, body size and body composition were controlled, boys had statistically significantly higher TB and FN BMC at all maturity levels (p < 0.05). No independent sex differences were found at the LS (p > 0.05).
  
  
  CONCLUSIONS
  Although a statistical significant sex effect is observed, it is less than the error of the measurement, and thus sex difference are debatable. In general, sex difference are explained by anthropometric difference.
authors.affiliation: College of Kinesiology, University of Saskatchewan, Saskatoon, Canada. baxter.jones@usask.ca
authors.forename: A D G
authors.initials: AD
authors.lastname: Baxter-Jones
authors.forename: R L
authors.initials: RL
authors.lastname: Mirwald
authors.forename: H A
authors.initials: HA
authors.lastname: McKay
authors.forename: D A
authors.initials: DA
authors.lastname: Bailey
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D001823:Body Composition / Q000502:physiology*; D001824:Body Constitution / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging; D002648:Child; D015331:Cohort Studies; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D012727:Sex Characteristics