Secular trends in skeletal maturity in South Africa: 1962–2001

BACKGROUND: Secular trends are usually monitored through changes in size and earlier maturation. Skeletal maturity has rarely been used as a biological indicator of secular trend. AIM: To observe secular changes in the skeletal maturity of urban South African adolescents between 1962 and 2001. SUBJECTS AND METHODS: Data from the Pretoria National Nutrition Survey were compared with a cross-sectional survey of children from the Johannesburg-Soweto based Birth to Twenty birth cohort study. Adolescents aged 9-11 years from each survey were included in the analysis. Skeletal maturity was assessed using the Greulich-Pyle technique. Height, weight, triceps and subscapular skinfolds were also measured. RESULTS: The skeletal maturity of white males and females in 2001 was in advance of the 1962 cohort by an average of 3.4 months and 2.0 months, respectively. Black males and females in 2001 were significantly in advance of the 1962 cohort by an average of 9.7 months and 15.8 months, respectively (p<0.01). CONCLUSION: Significant secular increases in the skeletal maturity of urban black South African children occurred between 1962 and 2001. Non-significant increases were seen in white children. The significant secular increases were concordant with increases in stature and adiposity during this period. The increase in skeletal maturity may reflect the removal of growth constraint, particularly in black children.