Bone Mass and Bone Size in Pre- or Early Pubertal 10-Year-Old Black and White South African Children and Their Parents
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Genetic factors are thought to maintain bone mass in socioeconomically disadvantaged black South Africans. We compared bone mass between environmentally disadvantaged black and advantaged white children and their parents, after determining the most appropriate method by which to correct bone mineral content (BMC) for size. We collected data from 419 healthy black and white children of mean age 10.6 years (range 10.0–10.9), 406 biological mothers, and 100 biological fathers. Whole-body, femoral neck, lumbar spine, and mid- and distal one-third of radius bone area (BA) and BMC were measured by dual-energy X-ray absorptiometry. Power coefficients (PCs) were calculated from the linear-regression analyses of ln(BMC) on ln(BA) and used to correct site-specific BMC for bone size differences. Heritability (½h2, %) by maternal and paternal descent was estimated by regressing children’s Z scores on parents’ Z scores. Correcting BMC for height, weight, and BAPC accounted for the greatest variance of BMC at all skeletal sites. In so doing, BMC in blacks was up to 2.6 times greater at the femoral neck and lumbar spine. Maternal and paternal heritability was estimated to be ~30% in both black and white subjects. These results may in part explain the lower prevalence of fragility fractures at the hip in black South African children when compared to whites. Heritability was comparable between environmentally disadvantaged black and advantaged white South African children and similar to that reported for Caucasians in other parts of the world.
KeywordsBone densitometry Population study Association South Africa Children Ethnicity
We acknowledge the contributions of Saeeda Mohamed and Thabile Sibiya for their DXA measurements. The Wellcome Trust of the United Kingdom and the Medical Research Council of South Africa funded this research.
- 1.Cameron N (1996) Birth to ten: the first five years. Leech 65:42–44Google Scholar
- 7.Solomon L (1968) Osteoporosis and fracture of the femoral neck in South African blacks. J Bone Joint Surg 50:2–13Google Scholar
- 14.Kalkwarf H, Zemel B, Gilsanz V, Lappe J, Horlick M, Oberfield S, Mahboubi S, Fan B, Frederick M, Winer K, Shepperd J (2007) The Bone Mineral Density in Childhood Study (BMDCS): bone mineral content and density according to age, sex and race. J Clin Endocrinol Metab 92:2087–2099PubMedCrossRefGoogle Scholar
- 17.Bachrach L (2000) Dual-energy X-ray absorptiometry (DEXA) measurements of bone density and body composition: promise and pitfalls. J Pediatr Endocrinol Metab 2:983–988Google Scholar
- 23.Lohman T, Roche A, Martorell R (1991) Anthropometric standardization reference manual. Human Kinetics, ChampaignGoogle Scholar
- 26.Tanner J, Whitehouse R, Cameron N (1983) Assessment of skeletal maturity and prediction of adult height. Academic Press, LondonGoogle Scholar
- 27.Bradshaw D, Steyn K (2001) Poverty and chronic diseases in South Africa. Technical report. Medical Research Council of South Africa, Cape TownGoogle Scholar