4 Discussion
The current systematic review provides a quantitative estimate of the asthma control of the current ongoing COVID-19 pandemic in children. The COVID-19 outbreak and the measures taken to it have had significant influences on asthma control among children. We have shown for the first time that the level of asthma control was significantly improved during the COVID-19 pandemic compared to the same period before it, with a reduction of asthma exacerbation, asthma admission and emergency room visit. One reason of these results is probably associated with the lockdown measures during COVID-19 pandemic, which limit viral disease transmissions, reduce the possible exposure to asthma triggers, such as viral infections, outdoor allergens, physical activities, and air pollution21-23. It might also be explained by caregivers’ afraid to bring children to hospital because of the risk of exposure to SARS‐Co-V224. And increased treatment adherence is also an important factor. Caregivers are afraid of going to hospital in the special time, so they pay more attention to their health than that before the pandemic and treat their children’s asthma in time, and take the treatment actively, thus the times of visits to the hospital has decreased and the frequency of asthma exacerbation has also decreased. Anyway, these results mean less medication and healthcare resources are used in the control of children’s asthma.
The outcome of use of inhaled corticosteroids and Beta-2 agonists shows no significant difference. In fact, on one hand, a lot of children reduced their maintenance therapy (use of inhaled corticosteroids and Beta-2 agonists), it is likely because of the good level of disease control, in the study of Ullmann et al.18 showed the significant reduction of respiratory symptoms, which meant there was a real improvement in asthma control. On the other hand, there are some children stepped up their therapy during the lockdown. It was not only because of symptoms or the fear and anxiety related to the spreading of the COVID‐19 pandemic25-27. Also, studies have suggested that inhaled corticosteroids may enhance innate immunity to viral infections28,29, reduce susceptibility to severe respiratory viral infections and can downregulate virus angiotensin-converting enzyme-2 receptor expression in the airways in the case of SARS-CoV-230.
The outcome of c-ACT scores were not analyzed, though many articles included it. It was mainly because of the different manifestations used. For example, Papadopoulos et al.17 use number of people to show improved scores. Jia et al.16 use the number of people whose scores were greater or equal to 20 which means good control. Ullmann et al.18 use the exact scores directly. Yucel et al.19 use the ratio of score less than 20. So it is hard to unite these outcomes. This is a problem that needs to be unified in the follow-up studies.
Although the current meta-analysis results show that the control of asthma in children has been improved during pandemic, we are still concerned about the question that will childhood asthma worsen if the lockdown continues for a very long time? The asthma control of patients with indoor allergen sensitization might be worse. Confounding factors such as increased exposure to indoor allergens, such as HDMs, molds, pet allergens, and decreased exposure to seasonal outdoor allergens such as pollens may have both negative and positive effects respectively on asthma. Further researches are needed.
After the COVID-19 disappearing, children suffering from asthma and their caregivers should still reduce exposure to asthma triggers like viral infections, outdoor allergens, and air pollution, at the same time increase treatment adherence, just do what they underwent in the pandemic, thus to restore, maintain and promote effective asthma management for children, this is the meaning of our writing this article.
Our review has several limitations. First, the sample size of this meta-analysis was relatively small. As a result, the unknown risk of bias caused by incomplete data could constrain our results. Second, our results are based on observational studies, which are susceptible to design bias, selection bias and residual confounding. Third, in this study was that heterogeneity across the studies was substantial, which could be attributed to different definition of severity used or sample size. Despite these limitations, this meta-analysis provides information on the association between children’s asthma control and COVID-19 pandemic.