Asthma Not an Independent Predictor of COVID-19 Outcome

By Megan Brooks

March 03, 2021

NEW YORK (Reuters Health) - Asthma is not an independent risk factor for hospitalization or more severe illness from SARS-CoV-2 infection and allergic asthma may actually be protective, according new research.

There has been conflicting data regarding the effect of comorbid asthma on the severity of COVID-19, with some studies suggesting that asthma is a risk factor for more severe disease and others suggesting that isn't case, Dr. Lauren Eggert of Stanford University School of Medicine in California explained in a presentation at the American Academy of Allergy, Asthma and Immunology (AAAAI) virtual annual meeting.

Some data also show that the Th2 inflammation associated with the allergic asthma subtype downregulates the ACE2 receptor, which has been shown to be the port of entry for the SARS-CoV-2 virus, conferring a potential protective effect, she said.

To investigate further, the researchers studied all 5,596 patients who tested positive for SARS-CoV-2 at Stanford Health Care over six months (March to September 2020). Of these, 11% were hospitalized, including 100 (16.5%) patients with asthma. All baseline characteristics of the patients were comparable, except hospitalized patients tended to be older.

In the initial univariate analysis, asthma was significantly associated with hospitalization for COVID-19 (odds ratio, 1.53; 95% confidence interval, 1.2 to 1.93).

However, many of the patients had comorbid conditions known to be associated with more severe COVID illness, including hypertension, coronary heart disease, diabetes and obesity. After adjustment for these factors, "asthma was no longer a risk factor for hospitalization" (OR, 1.12; 95% CI, 0.86 to 1.45), Dr. Eggert reported.

Asthma was also not significantly associated with COVID-19 disease severity among hospitalized inpatients (OR, 1.21; 95% CI, 0.8 to 1.85). "Disease severity was defined very rigorously through chart review, according to the NIH severity scale," she noted.

"And what's very interesting," said Dr. Eggert, "is that when we stratified by allergic asthma versus non-allergic asthma, we found that having a diagnosis of allergic asthma actually conferred a protective effect. There was almost half the risk of hospitalization in asthmatics with allergic asthma as compared to others."

She also noted that eosinophil levels during hospitalization, even when adjusted for systemic steroid use, correlated with better outcomes, independent of asthmatic status.

Summing up, Dr. Eggert said, "in this cohort of patients tested for SARS-CoV-2 at Stanford, asthma was not an independent risk factor, in and of itself, for hospitalization, or more severe COVID-19 disease and allergic asthma actually decreased the risk of hospitalization by nearly half."

Going forward, Dr. Eggert said it will be important for others to do similar studies.

"There is also a lot of interest in how this might affect our patients on biologics, which deplete eosinophils and kind of get rid of that allergic phenotype. Does that have any effect on disease severity? Unfortunately, the number of patients on biologics was very small in our cohort, but I do think this is an interesting area for exploration," she concluded.

SOURCE: AAAAI virtual annual meeting, February 26 to March 1, 2021.