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Can urbanization increase asthma and allergy risk through the infant microbiota?

Published online: December 14, 2020

Urbanization is a global megatrend. It is estimated that 70% of people are living in urban areas and this proportion is predicted to increase even further in coming decades. More and more babies are therefore starting their life in an urban environment. In a study recently published in The Journal of Allergy and Clinical Immunology (JACI), Lehtimäki and colleagues suggests that the urban living environment can have major consequences for the health of children.

The researchers followed 700 children from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC2010) mother-child cohort, who were born and spent their first year of life either in an urban or rural environment in Denmark. These children had been carefully monitored since their birth in around 2010, and numerous samples were collected in their first year of life both from gut and airways to evaluate how the microbial communities within their bodies develop. Through their childhood and until the children were six years old, the study physicians evaluated whether the children developed asthma, eczema and allergy.

Children who were born and spend their early life in urban environments were more likely to develop asthma, allergic rhinitis and allergic sensitization to aeroallergens at age six years than rural children. The bacterial composition of both airway and gut differed between children from urban or urban environments, and especially children with an urbanized microbiota composition during their first year of life were predisposed to develop these diseases. The researchers discovered that a potential link between the urbanized infant microbiota and the increased risk of asthma and allergic disorders could be a disturbed development of immune function among urban children.

This new study suggests that the living environment very early in life can have major impact on health later in life. Differing microbial exposures in rural and urban areas influence the development of the immune system, which in this period undergoes an intensive training to react adequately to outer exposures. The findings suggest that rural environments provide beneficial microbial exposures that can guide the maturation of the immune system in a positive direction. The researchers argue that we should try to find ways to introduce the beneficial rural microbes to children growing up in urban areas to prevent disease in the future.

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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