title: Body mass index at 11 years and bone mass at age 18: path analysis within the 1993 Pelotas (Brazil) birth cohort study.
abstract: BACKGROUND
  We investigated whether Body Mass Index (BMI) at 11 years old has a direct effect on bone mass at age 18 operating through alterations to bone growth and development, or whether the association is mediated by concurrent BMI, fat mass (FM), and fat free mass (FFM).
  
  
  METHODS
  Path analysis was used to explore the association between BMI at age 11 and whole-body bone mineral content (BMC) and bone mineral density (BMD) assessed by dual-energy x-ray absorptiometry (DXA) at age 18 in a prospective birth cohort study comprising 3,307 adolescents; we also evaluated the degree to which this association was mediated by BMI, FM (kg) and FFM (kg) assessed by plethysmography (BOD POD) at age 18.
  
  
  RESULTS
  We found a positive association between BMI at age 11 and BMC (males [β = 179.7 g, 95% CI 161.4; 198.0]; females [β = 179.9 g, 95% CI 165.3; 194.6]) and BMD (males [β = 0.030 g/cm2, 95% CI 0.024; 0.035]; females [β = 0.029 g/cm2, 95% CI 0.025; 0.033]) at age 18. This association was largely mediated by BMI and FFM at age 18 in both female and male adolescents. FM at age 18 was not an important mediator.
  
  
  CONCLUSIONS
  Concurrent BMI and FFM were the main mediators of the association between BMC/BMD in late adolescence and BMI in early adolescence.
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. ludmuniz@yahoo.com.br.
authors.forename: Ludmila Correa
authors.initials: LC
authors.lastname: Muniz
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. anamene@terra.com.br.
authors.forename: Ana Maria Baptista
authors.initials: AM
authors.lastname: Menezes
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. cecilia.epi@gmail.com.
authors.forename: Maria Cecília Formoso
authors.initials: MC
authors.lastname: Assunção
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. jeovanymm@yahoo.es.
authors.forename: Jeovany
authors.initials: J
authors.lastname: Martínez-Mesa
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. fcwehrmeister@yahoo.com.br.
authors.forename: Fernando Cesar
authors.initials: FC
authors.lastname: Wehrmeister
authors.affiliation: MRC Integrative Epidemiology Unit at the University of Bristol, School of Social and Community Medicine, University of Bristol, Bristol, UK. laura.howe@bristol.ac.uk.
authors.forename: Laura D
authors.initials: LD
authors.lastname: Howe
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. prchallal@gmail.com.
authors.forename: Pedro Curi
authors.initials: PC
authors.lastname: Hallal
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. hdgs.epi@gmail.com.
authors.forename: Helen
authors.initials: H
authors.lastname: Gonçalves
authors.affiliation: Post-Graduate Program in Epidemiology, Federal University of Pelotas, Rua: Marechal Deodoro 1160 (3° andar). CEP, Pelotas, Rio Grande do Sul, 96020-220, Brasil. fcbarros.epi@gmail.com.
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Barros
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000502:physiology*; D000293:Adolescent; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D001938:Brazil; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010991:Plethysmography; D011446:Prospective Studies; D012189:Retrospective Studies; D012737:Sex Factors