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Asthma Phenotypes and COVID-19 Risk: A Population-based Observational Study

Publication date: 

19 Oct 2021


American Journal of Respiratory and Critical Care Medicine, ISSN: 1073-449X


Bloom CI, Cullinan P, Wedzicha JA

Publication type: 



Rationale: Studies have suggested some asthma patients are at risk of severe COVID-19, but they have had limited data on asthma phenotype and have not considered if risks are specific to COVID-19. Objectives: Determine the effect of asthma phenotype on three levels of COVID-19 outcomes. Compare hospitalisation rates to influenza and pneumonia. Methods: Electronic medical records were used to identify asthma patients and match them to the general population. Patient-level data were linked to Public Health England SARS-CoV-2 test data, hospital, and mortality data. Asthma was phenotyped by medication, exacerbation history, and type-2 inflammation. The risk of each outcome, adjusted for major risk factors, was measured using Cox regression. Measurements and Main Results: 434,348 asthma and 748,327 matched patients were included. All asthma patients had a significantly increased risk of a GP-diagnosis of COVID-19. Asthma with regular inhaled corticosteroid (ICS) use (HR=1.27, 95%CI=1.01-1.61), intermittent ICS + add-on asthma medication use (HR=2.00, 95%CI=1.43-2.79), regular ICS + add-on use (HR=1.63, 95 CI=1.37-1.94), or with frequent exacerbations (HR=1.82, 95% CI=1.34-2.47) was significantly associated with hospitalisation. These phenotypes were significantly associated with influenza and pneumonia hospitalisations. Only patients with regular ICS + add-on asthma therapy (HR=1.70, 95%CI=1.27-2.26) or frequent exacerbations (HR=1.66, 95%CI=1.03-2.68) had a significantly higher risk of ICU admission or death. Atopy and blood eosinophil count were not associated with severe COVID-19 outcomes. Conclusions: More severe asthma was associated with more severe COVID-19 outcomes, but type-2 inflammation was not. The risk of COVID-19 hospitalisation appeared to be similar to the risk with influenza or pneumonia.