Asthma is not an independent risk factor for more severe disease or hospitalization due to COVID-19, according to recent research presented at the annual meeting of the American Academy of Allergy, Asthma, and Immunology, held virtually this year.
“In our cohort of patients tested for SARS-CoV-2 at Stanford between March and September, asthma was not an independent risk factor in and of itself for hospitalization or more severe disease from COVID,” Lauren E. Eggert, MD, of the Sean N. Parker Center for Allergy and Asthma Research at Stanford (Calif.) University, said in a poster presentation at the meeting. “What’s more, allergic asthma actually decreased the risk of hospitalization by nearly half.”
Dr. Eggert noted that there have been conflicting data on whether comorbid asthma is or is not a risk factor for more severe COVID-19. “The general thought at the beginning of the pandemic was that because COVID-19 is predominantly a viral respiratory illness, and viral illnesses are known to cause asthma exacerbations, that patients with asthma may be at higher risk if they got COVID infection,” she explained. “But some of the data also showed that Th2 inflammation downregulates ACE2 receptor [expression], which has been shown to be the port of entry for the SARS-CoV-2 virus, so maybe allergy might have a protective effect.”
The researchers at Stanford University identified 168,190 patients at Stanford Health Care who had a positive real-time reverse transcriptase polymerase chain reaction (RT-PCR) test for SARS-CoV-2 between March and September 2020 and collected data from their electronic medical records on their history of asthma, if they were hospitalized, comorbid conditions, and laboratory values. Patients who had no other data available except for a positive SARS-CoV-2 result, or were younger than 28 days, were excluded from the study. Dr. Eggert and colleagues used COVID-19 treatment guidelines from the National Institutes of Health to assess disease severity, which grades COVID-19 severity as asymptomatic or presymptomatic infection, mild illness, moderate illness, severe illness, and critical illness.
In total, the researchers analyzed 5,596 patients who were SARS-CoV-2 positive, with 605 patients (10.8%) hospitalized within 14 days of receiving a positive test. Of these, 100 patients (16.5%) were patients with asthma. There were no significant differences between groups hospitalized and not hospitalized due to COVID-19 in patients with asthma and with no asthma.
Among patients with asthma and COVID-19, 28.0% had asymptomatic illness, 19.0% had moderate disease, 33.0% had severe disease, and 20.0% had critical COVID-19, compared with 36.0% of patients without asthma who had asymptomatic illness, 12.0% with moderate disease, 30.0% with severe disease, and 21.0% with critical COVID-19. Dr. Eggert and colleagues performed a univariate analysis, which showed a significant association between asthma and COVID-19 related hospitalization (odds ratio, 1.53; 95% confidence interval, 1.2-1.93; P < .001), but when adjusting for factors such as diabetes, obesity coronary heart disease, and hypertension, they found there was not a significant association between asthma and hospitalization due to COVID-19 (OR, 1.12; 95% CI, 0.86-1.45; P < .40).
In a univariate analysis, asthma was associated with more severe disease in patients hospitalized for COVID-19, but the results were not significant (OR, 1.21; 95% CI, 0.8-1.85; P = .37). When analyzing allergic asthma alone in a univariate analysis, the researchers found a significant association between allergic asthma and lower hospitalization risk, compared with patients who had nonallergic asthma (OR, 0.55; 95% CI, 0.31-0.92; P = .029), and this association remained after they performed a multivariate analysis as well.
“When we stratified by allergic asthma versus nonallergic asthma, we found that having a diagnosis of allergic asthma actually conferred a protective effect, and there was almost half the risk of hospitalization in asthmatics with allergic asthma as compared to others, which we thought was very interesting,” Dr. Eggert said.
“Eosinophil levels during hospitalization, even when adjusted for systemic steroid use – and we followed patients out through September, when dexamethasone was standard of care – also correlated with better outcomes,” she explained. “This is independent of asthmatic status.”