title: Peak bone mineral density, lean body mass and fractures.
abstract: BACKGROUND
  During childhood and adolescence, bone mass and lean body mass (LBM) increase till a plateau is reached. In this longitudinal and cross-sectional study, the age of reaching the plateau was evaluated for lumbar spine and total body bone mass measurements and lean body mass. The association between fractures and bone mineral density (BMD) was studied.
  
  
  METHODS
  We included 501 healthy participants, 141 males and 360 females, aged 13-29 years. Of these 90 had participated in a previous longitudinal study of 444 participants, aged 4-20 years (for the first measurement) and 198 participants, aged 8-25 years (for a second measurement). BMD and body composition were measured with dual energy X-ray absorptiometry (DXA). Volumetric BMD (bone mineral apparent density, BMAD) was calculated. All the data were used to determine the age of reaching the plateau.
  
  
  RESULTS
  The plateau for lumbar spine BMD, BMAD, total body BMD, bone mineral content and LBM was reached between 18 and 20 years of age in females and between 18 and 23 years in males. The prevalence of fractures was 37% in males and 28% in females. Total body BMD Z-score was significantly lower in all participants who had had a fracture (p<0.05), whereas lumbar spine BMD and BMAD was only significantly lower in females who had had fractures (p=0.007 and p<0.001, respectively). Mean lumbar spine BMAD Z-score at the previous measurement was significantly lower in the participants who had a first fracture between the last two measurements (p=0.04).
  
  
  CONCLUSIONS
  Peak BMD and peak LBM were attained between 18 and 20 years in females and between 18 and 23 years in males in this study using longitudinal and cross sectional data in the age range of 4 to 30 years. A significantly lower total body BMD was seen in participants who had had a fracture and a lower lumbar spine BMD and BMAD in females who had had a fracture. Lumbar spine BMAD Z-score seems to be a good predictor for future fractures.
authors.affiliation: Department of Pediatrics, Division of Endocrinology, University Medical Center Groningen, Beatrix Children's Hospital, Groningen, The Netherlands. a.m.boot@bkk.umcg.nl
authors.forename: Annemieke M
authors.initials: AM
authors.lastname: Boot
authors.forename: Maria A J
authors.initials: MA
authors.lastname: de Ridder
authors.forename: Inge M
authors.initials: IM
authors.lastname: van der Sluis
authors.forename: Ingrid
authors.initials: I
authors.lastname: van Slobbe
authors.forename: Eric P
authors.initials: EP
authors.lastname: Krenning
authors.forename: Sabine M P F de Muinck
authors.initials: SM
authors.lastname: Keizer-Schrama
mesh_terms: D000293:Adolescent; D000328:Adult; D001835:Body Weight / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D050723:Fractures, Bone / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D013851:Thinness / Q000503:physiopathology*; D055815:Young Adult