Health benefits of living in cities for children and teens diminishing: Study

The advantages of living in cities for young people's healthy growth and development are shrinking across much of the world, according to a global analysis of trends in child and adolescent height and body mass index (BMI).

The research, by a global consortium of over 1500 researchers and physicians, 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 study, published recently in the journal Nature, 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 researchers also assessed children’s BMI, an indicator of whether they have a healthy weight for their height.

They 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 1.1 kilogrammes per square metre (kg/m²) globally, the researchers said.

"Cities continue to provide considerable health benefits for children and adolescents," said Anu Mishra, lead author of the study, from Imperial College London’s School of Public Health.

"Fortunately, in most regions, rural areas are catching up to cities thanks to modern sanitation and improvements in nutrition and healthcare," Mishra 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, the researcher added.

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.

"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," said Professor Majid Ezzati, senior author for the study, from Imperial College London. 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.

"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," Ezzati added.

The trend in sub-Saharan Africa is also a cause for concern, the researchers said.

“Rural sub-Saharan Africa is now the global epicentre of poor growth and development for children and adolescents," said Professor Andre Pascal Kengne, co-author for the study, from the South African Medical Research Council.

"As the cost of food skyrockets and countries finances get worse due to the COVID-19 pandemic and the war in Ukraine, the rural poor in Africa are at risk of falling further behind," Kengne said.

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, the researchers added.