Life in the city has historically had a series of benefits for the growth and development of children and adolescents compared to the rural environment.
In 1990, urban children were a few centimeters taller than rural children in almost every country in the world, except in high-income countries, where this gap was less than one centimeter difference.
Research published this Wednesday in the journal
Nature
with data from 194 countries between 1990 and 2020 shows that in the last three decades this difference has been reduced and, in the case of the most developed countries, almost blurred.
In Spain, the children of the villages have grown one centimeter in the last thirty years and have caught up with those of the city.
In the case of Spanish girls, those who live in rural areas have even surpassed those in urban areas and are eleven millimeters taller.
Diet, socioeconomic situation or access to social and health services, in addition to genetics, are determining factors for development and growth.
In recent decades, the expansion of the welfare state in most of the world has made living conditions in rural areas improve and are on par with cities, explains David Cámara, a demographer at the University of Jaén, unrelated to this work.
"Now in a town you don't eat worse than in a city, nor do you get sicker," he says.
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For Andrea Rodríguez, principal investigator of the project, height is the best indicator of a child's nutritional status and well-being.
She reflects on the conditions in which it grows: "If his diet and development environment aren't optimal, he won't grow as tall as he should," she says.
Rodríguez, who is a biotechnologist at Imperial College London, explains that one of the regions that has reduced this difference the most in the last thirty years is Latin America.
Along with Central Europe and various parts of Asia, the gap in these regions has fallen by between 1 and 2.5 centimeters in the last three decades.
In countries like Mexico, China and Hungary this difference oscillated in 1990 between 2.4 and 5 centimetres.
However, in Andean countries such as Bolivia and Peru, children in cities still measured up to 4.7 centimeters taller than those in towns in 2020.
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At the other extreme is sub-Saharan Africa, where this gap in the height of children and adolescents in cities and rural areas has not only not decreased, but in some cases has even increased.
Countries like Ethiopia, the Democratic Republic of the Congo, Mozambique and Rwanda, reached a difference of 4.2 centimeters in the case of boys in 2020, according to the research.
More information:
University students are three centimeters taller than those who only have primary school studies
Height and socioeconomic factors go hand in hand, says José Miguel Martínez, professor of History and Economic Institutions at the University of Murcia.
“Belonging to a wealthy family confers health advantages, which translate into longer life expectancy and taller height,” he adds.
The historian maintains that currently the urban environment even poses more challenges than before due to factors such as the increase in inequality and the cost of living, the increase in housing prices or precariousness.
"Greater risks of poverty, social exclusion and, as a consequence, worse nutrition are concentrated."
In addition, he doubts that this equalization was not given so much to the improvement of conditions in the towns, but to the worsening of life in the cities.
Manuel Franco, professor of epidemiology at the University of Alcalá de Henares and at Johns Hopkins is blunt: the socioeconomic factor is a determining factor in what surrounds each person, how they eat, even in their education.
Last year, a study by David Cámara, a demographer at the University of Jaén, published in the journal
SSM - Population Health
determined that adults with university studies were three centimeters taller than those with only primary education.
Different 'spurts'
The demographer does not believe that in the countries where the gap has been reduced, the number of children in the cities has decreased.
Rather, that the minors of the towns have increased that height that differentiated them at a faster rate in the last decades.
This is thanks to better living conditions and food, he says.
Andrea Rodríguez, principal investigator of the project, confirms her theory: "It's like when two children hit the growth spurt at different times, but in the end they end up equaling each other."
For Cámara, one of the limitations of the research is that when the height of children is studied, it is not possible to know with certainty if the rate of development slows down or if there is "a different tempo."
It won't be known if there really is an intergenerational decline until adulthood, she says.
Martínez, from the University of Murcia, sees it as plausible that changes in the diet of young people and in lifestyles create an environment that is not very conducive to adolescent growth.
The historian talks about the fact that they have moved away from the Mediterranean diet and have more sedentary habits: "We are growing in width and some studies link the spread of obesity with the stagnation of altitude."
Being overweight in girls causes the first period to come forward and this may be related to a stoppage in growth, says Cámara.
In the study, the authors also mention the question of the onset of menstruation, something that they have not been able to verify because there are no globally comparable data on the age of menarche and the time of pubertal growth (the increase in height due to the release of of growth and sexual hormones), they allege.
What is clear, affirms the demographer, is that currently living in towns or cities does not imply the substantial differences that decades ago.
The rural environment "does not imply a peasant and poor life", especially in more developed countries.
Each time the ways of life and diet in the two areas are more similar and become identical, which defines the growth of children and adolescents and has allowed those who live in the villages to stop being left behind, he concludes .
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