Variability in the anthropometric status of four South African populations

Abstract

Coefficients of variation (V) of 4 populations were compared for each of 11 parameters. Males differed significantly in cristal height and 3 skinfolds. It has been suggested that negroids vary more in relation to their means in cristal height because of the onset of differential growth of the lower limbs. Relatively large Vs in skinfold measurements of White and Indian boys, notably those of the trunk, arose because there were more obese individuals with extreme values in the White and Indian populations than in the Cape Coloured and negroid populations. In females, leg circumferences and subscapular skinfolds differed significantly. Leg circumference Vs of Indian females were probably enhanced as a result of variably high adiposity in the calf region. The presence of extreme values in obese girls of this group had been the cause of raised Vs in subscapular skinfold measurements. There appear to be three periods during which the Vs of males and females differed: males varied more than females at the ages of 6 and 7 years; then females varied more until between 13 and 15 years, when males again became more variable. White males, however, varied more than White females in skinfolds. This may be caused by the presence of extreme values at either end of the distribution graph of both 'over-optimal' nutrition and undernutrition. It is shown that confidence limits based on a central value of the standard deviation (a) do not take into account the increasing variability with age noted in most parameters in populations of growing individuals. In future studies, variability changes should be shown by placing polynomials into one of the categories described n this article.

S. Afr. Med. J., 48, 643 (1974).