The effect of ethnicity on appendicular bone mass in white, coloured and Indian schoolchildren

Ethnic differences in the incidence and prevalence of osteoporosis have been shown throughout the world. In South Africa the prevalence of osteoporosis is much higher in whites than in blacks. This is surprising, since factors that might predispose to reduce bone mass are more preponderant in black communities. The present research was undertaken to determine whether differences in bone mass during the period of bone accretion could explain the difference in the incidence of osteoporosis. In this paper we report on differences in appendicular bone mass between white, coloured and Indian children and teenagers (6-18 years) from Johannesburg. The effects of weight, height, puberty and skinfold thickness on bone mass were also assessed. The bone width (BW) of white boys was greater than that of Indian boys, while the bone mineral content (BMC) and BMC/BW were greater in white boys than in both Indian and coloured boys. After adjustment for differences in weight and height, the BW of coloured boys was significantly greater than that of white boys, while all differences in BMC and BMC/BW became non-significant. For girls there were no significant differences in bone mass measurements, but after adjustment for height and weight coloured girls had significantly greater BMC and BMC/BW than either white or Indian girls. This greater weight- and height-adjusted bone mass in coloured girls is consistent with the impression of a lower incidence of osteoporosis in coloured women than in white women.