1 Introduction
Environmental exposures such as maternal smoking, socio-economic status, family structures, mode of delivery, diet, air pollutants and allergens are well-known risk factors for childhood asthma.1,2 A strong risk factor for increased asthma incidence and severity are also frequent lower respiratory tract infections and multiple-trigger wheezing during early life, which are significant predictors for the subsequent development of asthma later in life.3,4
The relationship between asthma and respiratory infections has made asthma an empirical risk factor for severe COVID-19 disease since the beginning of the pandemic. Although this relationship remains to date inconclusive with some reports suggesting that childhood asthma may be even protective against COVID-19,5 at least during the first months of the pandemic, COVID-19 control strategies characterised asthmatic adults and children as potentially vulnerable subpopulations.6
COVID-19 control strategies focused on containment of the spread of COVID-19 and involved national lockdowns, social distancing, compulsory use of masks and, following the roll-out of SARS-Cov-2 vaccines, campaigns and assessment of vaccination status upon entering indoor micro-environments. Not surprisingly, these strategies, combined with concerns of contracting the virus, have resulted in behavioural changes in the population, that, in turn, may have affected the epidemiology of common chronic diseases such as childhood asthma.7Decreased time spent outdoors, leading to reduced exposure to ambient environmental triggers such as allergens, pollutants and dust-related particulate matter,8 as well as reduction of social interactions that led to decreased exposure to communicable pathogens such as the influenza virus, respiratory syncytial virus (RSV) and rhinoviruses (RV) are the most relevant behavioural alterations that may have affected asthma morbidity.9 In addition, other COVID-19 control strategies also included stricter hand hygiene, while during peak periods of the pandemic waves access to hospital or primary care practitioners was restricted or avoided. In the case of children with asthma, national containment strategies also involved school closures,10 as well as restriction of after school (mostly outdoor) activities.8 Published evidence over the last two years has consistently documented a marked reduction of asthma morbidity during the COVID-19 period, mainly in terms of reduced exacerbation-related hospital and emergency department (ED) encounters.11-16
The aim of this review is to summarize the behavioural changes observed in asthmatic children during the implementation of COVID-19 containment strategies, present the concurrent improvement of childhood asthma morbidity and discuss the possible implications of these observations for public health and clinical practice in the post-COVID-19 era.