Abstract
ABSTRACTThere are no longitudinal pQCT data of bone growth and development from sub‐Saharan Africa, where rapid environmental, societal, and economic transitions are occurring, and where fracture rates are predicted to rise. The aim of this study was to compare skeletal development in black and white South African adolescents using longitudinal data from the Birth to Twenty study. The Birth to Twenty Bone Health subcohort consisted of 543 adolescents (261 [178 black] girls, 282 [201 black] boys). Annual pQCT measurements of the radial and tibial metaphysis and diaphysis were obtained between ages 12 and 22 years (distal metaphysis: cross‐sectional area [CSA] and trabecular bone mineral density [BMD]; diaphysis: total and cortical CSA, cortical BMD, and polar stress‐strain index [SSIp]). Age at peak height velocity (APHV) was calculated to account for differences in maturational timing between ethnic groups and sexes. Mixed‐effects models were used to describe trajectories for each pQCT outcome. Likelihood‐ratio tests were used to summarize the overall difference in trajectories between black and white participants within each sex. APHV (mean ± SD years) was similar in black (11.8 ± 0.8) and white (12.2 ± 1.0) girls, but delayed in black (14.2 ± 1.0) relative to white boys (13.3 ± 0.8). By 4 years post‐APHV, white adolescents had significantly greater cortical CSA and SSIp than black adolescents at the radius. There were no significant differences at the radial metaphysis but there was some divergence, such that black adolescents had greater radial trabecular BMD by the end of follow‐up. At the tibia, white adolescents had lower diaphyseal CSA and SSIp, and greater metaphyseal CSA. There was no ethnic difference in tibial trabecular BMD. There are ethnic differences in bone growth and development, independent of maturation, in South African adolescents. This work gives new insights into the possible etiology of childhood fractures, which occur most commonly as peripheral sites. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.
Highlights
Growth and development of the skeleton are important determinants of subsequent bone health in adulthood
The number of people at risk of osteoporotic fracture is predicted to double by 2040, with demographic changes shifting much of this burden to low-income and middle-income countries,(16) but there is a lack of prospective fracture data from sub-Saharan Africa, and no longitudinal studies linking changes in bone structure or mineral density during childhood and adolescence to peak bone mass
We aimed to understand how ethnic differences in peripheral quantitative computed tomography (pQCT) measurements track or change during adolescence in South African black and white boys and girls, and whether previously described differences in early adolescence were retained into early adulthood, and whether those differences were independent of maturational differences between ethnic groups
Summary
Growth and development of the skeleton are important determinants of subsequent bone health in adulthood. Comparisons of musculoskeletal phenotype in children between groups with different adult fracture risk may help define the structural determinants of bone health across the lifecourse.[1] The Bone Health subcohort of the Birth-to-Twenty (Bt20) cohort provides an opportunity to address this with longitudinal peripheral quantitative computed tomography (pQCT) measures of bone in black and white adolescents from Johannesburg, South Africa. Elsewhere prospective DXA data have been collected in the Bone Mineral Density in Childhood Study (US) and Saskatchewan Pediatric Bone Mineral Accrual Study (Canada).(18,19) In the University of British Columbia Healthy Bone Study, prospective measures of pQCT and high resolution pQCT (HRpQCT) were collected and have recently been reported.[20,21] Using longitudinal growth data from the UK National Survey of Health and Development, the timing of pubertal growth (determined either by age at menarche, voice breaking, or by Super Imposition by Translation and Rotation [SITAR]) and height and weight growth patterns were related to bone health in early old-age (60 to 64 years).(22–24) Together, these studies have shown that the amount of longitudinal growth, weight change, and bone mineral accrual during adolescence are important predictors of adulthood bone health and future risk of osteoporotic fracture.[25,26]
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