• Asthma Epidemiology
• Child

Asthma is the most prevalent chronic disease of childhood. Based on the Global Burden of Diseases, Injuries and Risk Factors Study, the global incident cases of asthma in children increased by 7.07% from 1990 to 2019, the highest incidence being observed in children under 5 years old.1 Among these youngest children, asthma is difficult to diagnose, and is often defined by wheezing episodes characterised by their start date (early or late infancy) and/or their duration (transient or persistent).2 Epidemiological studies across different populations have revealed the key role of environmental factors in influencing the evolution from wheezing in early life to asthma, including genetic predisposition, viruses, allergic sensitisation, early-life exposure to tobacco smoke and interaction with the microbiome.3 It is now better recognised that exposure to poor outdoor and indoor air quality affects respiratory health throughout life, starting from the antenatal period onwards, and children living in low- and middle-income countries (LMICs) face increased challenges in terms of air quality, particularly due to additional sources of indoor pollution including increased reliance on solid fuels, open fires and rapid urbanisation.4 A better understanding of the associations between environmental factors, particularly those that are preventable, and the persistence of wheezing is essential for the prevention and management of asthma.

To date, results from longitudinal epidemiological studies on antenatal exposure …