The mean height of South African boys’ has stagnated, and both boys and girls in rural areas of sub-Saharan Africa have gone from being underweight to overweight, research by a global coalition has found.
MedicalBrief reports that research found that the healthy growth and development of children and adolescents living in cities has been reduced across many parts of the world, with previous health advantages no longer evident.
The study team comprised more than 1 500 scientists and physicians, including from the South African Medical Research Council’s (SAMRC) Non-Communicable Disease Research Unit, and was led by Imperial College London and published in Nature.
After trends in child and adolescent height and BMI were analysed, there was clear evidence that there were now far fewer health advantages to city living compared with rural lifestyles, said the scientists.
The analysis gathered height and weight data from 71m children and adolescents (aged five to 19) across urban and rural areas of 200 countries from 1990 to 2020. The data collected during that period (1990-2020) showed that school-aged children and adolescents in cities fared better in height than their rural counterparts.
However, this has since changed, the most recent research finding there is no longer a height difference between city and rural area inhabitants.
The experience in South Africa is one such example of the overall stagnating or reversing of height gains seen in sub-Saharan Africa.
For South African boys, mean height has stagnated in urban and rural areas over the past two decades, keeping the urban height advantage around 1.5cm by 2020. BMI increased for both South African boys and girls, but similar to their African peers, this increase happened faster for rural children and adolescents, and the urban-rural BMI difference was essentially closed by 2020.
Nutrition
The study also assessed children’s BMI as a reflection of the quality of nutrition and healthiness of the environment. On average, children living in cities had a slightly higher BMI than those in rural areas in 1990.
By 2020, BMI averages rose for most countries, while faster for urban children, except sub-Saharan Africa and south Asia, where BMI rose faster in rural areas.
Nevertheless, over the 30-year period, the gap between urban and rural BMI remained small: less than 1.1kg/m² globally (less than 2kg in weight for a child who is 130cm tall or less than 3kg in weight for an adolescent who is 160cm tall).
Dr Anu Mishra, lead author of the study, from Imperial College London’s School of Public Health, said: “The results of this large global study challenge the commonly held perceptions about the negative aspects of living in cities around nutrition and health.
“In fact, cities continue to provide considerable health benefits for children and adolescents. Fortunately, in most regions, rural areas are catching up, thanks to modern sanitation and improvements in nutrition and healthcare.”
While height and BMI has increased worldwide since 1990, the researchers found that the degree of change between urban and rural areas varied greatly among different middle and low-income countries, while small urban-rural differences remained stable across high-income countries.
The trend in sub-Saharan Africa is a cause for concern.
Boys living in rural areas have levelled in height or even become shorter over the three decades, partly due to the nutritional and health crises after the policy of structural adjustment in the 1980s.
Professor Andre Pascal Kengne, co-author for the study, from the SAMRC, said: “Rural sub-Saharan Africa is now the global epicentre of poor growth and development for children and adolescents. As the cost of food skyrockets and countries’ finances worsen, due to the pandemic and the war in Ukraine, the rural poor in Africa risk falling even further behind.”
Over time, boys and girls in sub-Saharan Africa also gained weight more rapidly in rural areas than cities, meaning in some countries, they went from being underweight to gaining too much weight for healthy growth.
Professor Majid Ezzati, senior author for the study, from Imperial College London’s School of Public Health added: “The issue is not so much whether children live in cities or urban areas, but where the poor live, and whether governments are tackling growing inequalities with initiatives like supplementary incomes and free school meal programmes.
“This is a serious problem at every level, from individual to regional. Faltering growth in school-aged children and adolescents is strongly linked to poor health through life, lost educational attainment and the immense cost of unrealised human potential.”
Study details
Diminishing benefits of urban living for children and adolescents’ growth and development
NCD Risk Factor Collaboration (NCD-RisC)
Published in Nature on 29 March 2023
Abstract
Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1,2,3,4,5,6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified.
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