title: Ethnic and sex differences in skeletal maturation among the Birth to Twenty cohort in South Africa.
abstract: OBJECTIVE
  To examine ethnic and sex differences in the pattern of skeletal maturity from adolescence to adulthood using a novel longitudinal analysis technique (SuperImposition by Translation And Rotation (SITAR)).
  
  
  METHODS
  Johannesburg, South Africa.
  
  
  METHODS
  607 boys and girls of black as well as white ethnicity from the Birth to Twenty bone health study, assessed annually from 9 to 20 years of age.
  
  
  METHODS
  Bone maturity scores (Tanner-Whitehouse III radius, ulna, and short bones (TW3 RUS)) assessed longitudinally from hand-wrist radiographs were used to produce individual and mean growth curves of bone maturity and analysed by the SITAR method.
  
  
  RESULTS
  The longitudinal analysis showed that black boys matured later by 7.0 SE 1.6 months (p<0.0001) but at the same rate as white boys, whereas black girls matured at the same age but at a faster rate than white girls (by 8.7% SE 2.6%, p=0.0007). The mean curves for bone maturity score consistently showed a midpubertal double kink, contrasting with the quadratic shape of the commonly used reference centile curves for bone maturity (TW3).
  
  
  CONCLUSIONS
  Skeletal maturity was reached 1.9 years earlier in girls than boys, and the pattern of maturation differed between the sexes. Within girls, there were no ethnic differences in the pattern or timing of skeletal maturity. Within boys, however, skeletal maturity was delayed by 7 months in black compared with white ethnicity. Skeletal maturation, therefore, varies differentially by sex and ethnicity. The delayed maturity of black boys, but not black girls, supports the hypothesis that boys have greater sensitivity to environmental constraints than girls.
authors.affiliation: Population Policy and Practice Programme, UCL Institute of Child Health, London, UK.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Cole
authors.affiliation: Centre for Global Health and Human Development, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: Emily K
authors.initials: EK
authors.lastname: Rousham
authors.affiliation: Department of Chronic Disease Epidemiology, School of Public Health, Yale University, New Haven, Connecticut, USA MRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Nicola L
authors.initials: NL
authors.lastname: Hawley
authors.affiliation: Centre for Global Health and Human Development, School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK MRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Noel
authors.initials: N
authors.lastname: Cameron
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Shane A
authors.initials: SA
authors.lastname: Norris
authors.affiliation: MRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: John M
authors.initials: JM
authors.lastname: Pettifor
mesh_terms: D000293:Adolescent; D000328:Adult; D001846:Bone Development / Q000502:physiology*; D002648:Child; D005006:Ethnicity; D005260:Female; D057238:Growth Charts; D050276:Hand Bones / Q000000981:diagnostic imaging / Q000254:growth & development*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D011859:Radiography; D012737:Sex Factors; D013019:South Africa; D014953:Wrist / Q000000981:diagnostic imaging / Q000254:growth & development*; D055815:Young Adult
keywords: Adolescent Health; Growth