Health benefits for children and teenagers in cities are ‘shrinking’ worldwide

The advantages for children and adolescents’ healthy growth and development as a result of growing up in a city environment are shrinking across much of the world.

That is the overriding message based on a global analysis of trends in child and adolescent height and body mass index (BMI) led by Imperial College London.

A global consortium of more than 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.

‘Rural areas are catching up to cities’

The new study, which has been published 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 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 is from Imperial College’s School of Public Health, and was the lead author of the study. He 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.”

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.

‘BMI averages rose for most countries’

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.”

Funding for the study came from UK R UK Research and Innovation (MRC), Wellcome Trust, the European Union, the AstraZeneca Young Health Programme, and the Jameel Institute.

Author: Simon Weedy

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