Black South African men have been getting taller over the past three decades – their current adult height of black men on the 170.7cm mark versus 166.9cm in 1971, found a University of Witwatersrand study. But whites remain 5cm taller, on average.
These are the key findings of a Wits University study analysing height records of people born between April and June in 1990, and published in the SA Journal of Child Health.
Compared to heights reported in 1971 in the South African Medical Journal, “adult black males are now on average 3.8cm taller”, according to the study team led by paediatrician Nonhle Ngcobo.
The 205 black males in her study were 170.7cm by the time they stopped growing, compared with 166.9cm in the 1971 group. No significant changes were found in the black females’ heights (158.2cm vs 158.9cm in 1971); white females (163.9cm vs 165.4cm); or white males (175.3cm vs 174.7cm).
Ngcobo and her colleagues from the SA Medical Research Council/Wits Developmental Pathways for Health Research Unit said the study of growth trends was a way to assess the physical health of populations and highlight social disparities.
“The core of the study involves comparing the secular trends in height among self-reported black and white racial groups in South Africa. 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,” the authors said.
Apart from having a normal genotype, “the potential for growth is strongly influenced by socio-economic, nutritional and health factors”, they wrote, adding that a 1978 study found that the height and weight of white children began to diverge from their peers by the age of two.
“The poorest growth was seen among rural black children and the best among urban white children,” said Ngcobo.
“The consistent hierarchy, from smallest to largest, was black rural, black urban, mixed ancestry urban, Indian urban and white urban.”
A 2003 study found the economic and social transition had not yet resulted in improved child growth, but the new study suggests there has been a breakthrough.
The researchers examined data on 569 children born in Johannesburg in 1990. Because the sample was short of white subjects, they recruited another 226 white children from Johannesburg schools.
They found that black girls and white girls stopped growing at almost the same age (15.1 years vs 15.3 years) but whites ended up 5.7cm taller (163.9cm vs 158.2cm).
White boys reached their adult height at 16.5, a full year before black boys, and on average were 4.6cm taller (175.3cm vs 170.7cm). These findings, said the authors, echoed a 2015 study that showed girls achieve skeletal maturity 1.9 years earlier than boys.
Interestingly, note the authors, studies have found a positive correlation between short stature and prevalence of cardiovascular disease while others find evidence that taller people have a higher risk of cancer.
The adverse effects of short stature during pregnancy, childbirth and child rearing are well established, but there is no consensus about the effect of height on longevity. Tall stature is also a proxy for social status and leadership in both men and women, which includes higher earning potential, and dominance in interpersonal interactions.[
Study details
The age at which adult height is achieved during adolescence in the Birth to Twenty Cohort, Johannesburg, South Africa
P N Ngcobo, L Nyati, S A Norris, J M Pettifor
Published in the South African Journal of Child Health, June 2021 Vol. 15 No. 2
Abstract
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.
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