The age at which adult height is achieved during adolescence in the Birth to Twenty Cohort, Johannesburg, South Africa

Background. The core of the study involves comparing the secular trends in height among self-reported black and white racial groups in South Africa (SA). The white group represents that part of the population that has always been affluent and therefore has growth trends comparable with those of developed nations of the world. In comparing the groups, we wanted to see the extent to which the black population has caught up, if it all, since the introduction of democracy in 1994. Objectives. To establish the age at which linear growth plateaus; to compare the age of growth cessation and the achieved adult height between sexes and racial groups in SA; and to compare data from the Bone Health Cohort with previous similar studies to ascertain the secular trend. Methods. We analysed prospective data of 569 individuals who had annual anthropometric assessments from age nine until 20 years (1999 - 2010). The SuperImposition by Translation and Rotation (SITAR) statistical programme was used to model height and age at growth cessation. Results. There was a total of 183 black females, 93 white females, 205 black males and 88 white males. Black and white females achieved adult height at a similar age (15.1 and 15.3 years), but black females were 5.7 cm shorter. Black and white males achieved their adult height at 17.5 and 16.5 years, respectively, black males being 4.6 cm shorter. Mean adult black male height is currently 170.7 cm v. 166.9 cm in 1971, while there were no significant secular changes in the other groups. Conclusions. There has been a positive secular growth trend in height over 30 years among black males, but no changes in the other groups.