A large systematic review of the effects of asthma on the risk of poor COVID-19 outcomes in adults and children found that, overall, asthma was not associated with severe COVID-19 outcomes, although the evidence supporting this conclusion was deemed to be of very low certainty. This was among the findings of an article recently published in BMJ Evidence-Based Medicine.
Early in the pandemic, it was expected that people with asthma would have a higher risk of adverse outcomes from COVID-19. The initial primary studies on this subject contradicted this expectation, reporting that people with asthma represented a lower proportion of patients with COVID-19 admitted to the hospital than that seen in the general population. Subsequent reviews and meta-analyses engendered conflicting conclusions, but analysis of the quality of these reviews showed important pitfalls. The current analysis, based studies spanning multiple continents, is one of the largest on the effects of asthma on the risk of poor COVID-19 outcomes, said the authors.
Conducted in the UK at Oxford University, this systematic review and meta-analysis sought to determine whether individuals with asthma were predisposed to experiencing worse cases of COVID-19. The researchers’ review of electronic databases in October 2020 yielded 30 studies that met inclusion criteria for the analysis. The studies all included at least 1 of the following outcome measures, stratified by asthma status: risk of SARS-CoV-2 infection, or hospitalization, intensive care unit admission, or mortality from COVID-19. Participants in all studies (n = 112,420) included adults and children who tested positive for or were suspected to have COVID-19. Among the 30 studies analyzed, 12 were deemed to be high quality, 15 medium quality, and 3 low quality. Notably, few provided indications of asthma severity. Certainty of findings was assessed using Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) criteria.
Investigators found that in people with asthma, allergic asthma was associated with lower COVID-19 risk, and concurrent chronic obstructive pulmonary disease was linked with higher risk. In some studies, corticosteroids correlated with higher risk, but this finding could simply imply higher risk in people with more severe asthma. In people with asthma, the risks associated with COVID-19 seem to go up with age, as seen in the general population. Pooled results showed that, overall, asthma was not associated with severe COVID-19 outcomes, although the evidence was judged to be of very low certainty.
Researchers noted that the chief limitations of their analysis findings were imprecision, possible publication bias, and unexplained statistical heterogeneity.
“Though the absence of evidence of a clear association between asthma and worse outcomes from COVID-19 should not be interpreted as evidence of absence,” cautioned the researchers, “the data reviewed do give some indication that risks in [people with asthma], as a whole, may be less than originally anticipated.” They recommend further high-quality primary studies to strengthen this assumption and to expedite the development of evidence-based shielding and avoidance measures, as well as proper vaccination schedules.
Otunla A, Rees K, Dennison P, et al. Risks of infection, hospital and ICU admission, and death from COVID-19 in people with asthma: systematic review and meta-analyses. BMJ Evid Based Med. Published online December 21, 2021. doi:10.1136/bmjebm-2021-111788