Diminishing health benefits of living in cities for children and teens

The advantages of living in cities for children and adolescents’ healthy growth and development are shrinking across much of the world, according to a new study.

The research, published in Nature, was led by Imperial College London and involved a global consortium of more than 1,500 researchers and physicians including from the University of Essex.

It analysed height and weight data from 71 million children and adolescents (aged 5 to 19 years) across urban and rural areas of 200 countries from 1990 to 2020.

Cities can provide a multitude of opportunities for better education, nutrition, sports and recreation, and healthcare that contributed to school-aged children and adolescents living in cities being taller than their rural counterparts in the 20th century in all but a few wealthy countries.

The new study found that in the 21st century, this urban height advantage shrank in most countries as a result of accelerating improvements in height for children and adolescents in rural areas.

The study also assessed children’s BMI - an indicator of whether they have a healthy weight for their height. The researchers found that on average children living in cities had a slightly higher BMI than children in rural areas in 1990. By 2020, BMI averages rose for most countries, albeit faster for urban children, except in 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: “Cities continue to provide considerable health benefits for children and adolescents. Fortunately, in most regions, rural areas are catching up to cities thanks to modern sanitation and improvements in nutrition and healthcare.

“The results of this large global study challenge the commonly held perceptions about the negative aspects of living in cities around nutrition and health.”

Co-lead Dr Honor Bixby, Research Fellow in epidemiology and population health at the Institute of Public Health and Wellbeing at the University of Essex, added: “Our study provides important evidence on inequalities in child and adolescent growth that have life-long consequences for health and quality of life.

“In parts of the world, gains in height have reduced disparities between children and adolescent in cities and rural areas and at the same time reduced disparities between wealthier and less wealthy nations. The most concerning trend we see is in rural sub-Saharan Africa, where children and adolescent height had remained persistently low or even in some cases declined, whilst weight has increased.”

While height and BMI has increased around the world 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.

Middle-income and emerging economies, such as Chile, Taiwan, and Brazil, have seen the biggest gains in rural children’s height over the three decades, with children living in rural areas growing to similar heights as their urban counterparts.

Professor Majid Ezzati, senior author for the study, from Imperial College London’s School of Public Health, said: “These countries have made great strides in levelling up. Using the resources of economic growth to fund nutrition and health programmes, both through schools and in the community, was key to closing the gaps between different areas and social groups.”

And contrary to the widespread assumption that urbanisation is the main driver of the obesity epidemic, the study found that many high-income western countries have had very little difference in height and BMI over time - with the gap between urban and rural BMI differing by less than one unit in 2020 (close to 1.5kg of weight for a child of 130cm).

Professor Ezzati 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.”