Does Asthma Lead to Worse COVID-19 Outcomes?

The coronavirus pandemic has evolved so rapidly that physicians have been forced to make decisions with incomplete information. It seems intuitive that patients with a respiratory disease such as asthma would be more likely to be infected with COVID-19, and once infected they would suffer higher morbidity and mortality compared with nonasthmatic persons. After all, asthma is characterized by airway obstruction, mucus production, and exacerbations and is treated using inhaled corticosteroids (ICSs) and oral corticosteroids (OCSs). An immunosuppressed patient with excess mucus in their lungs that is difficult to clear to due to airway obstruction seems the perfect host for COVID-19.

In medicine though, physiologic relationships and behaviors are usually more complicated than they appear. Asthma is not a single disease that affects a specific demographic. It's a heterogeneous syndrome comprising multiple phenotypes that develop across the age spectrum. Even in the absence of COVID-19, the interaction between ICS, OCS, and asthma phenotypes is complicated.

Are patients with asthma more likely to be infected with COVID-19? If so, are they more likely to be hospitalized or die of it? We're starting to get a clearer picture, and as predicted, it's not as straightforward as you may think.

Early reports didn't show a higher incidence of respiratory disease in patients hospitalized with COVID-19. Many of these studies came from rural China , though, where asthma prevalence in the overall population is difficult to quantify and may not be tracked. A study from New York City, using the electronic medical record to abstract comorbidity data, showed a 9% asthma prevalence in hospitalized patients with COVID-19. This is not far from the expected background prevalence in the United States. Data from England show that severe asthma is associated with worse outcomes, when "severe asthma" is defined as the need for corticosteroids in the previous 6 months. Survey data show an outpatient prevalence of asthma among patients with COVID-19 that is higher than the expected background. They also show that more hospitalized patients with COVID-19 have comorbid asthma compared with infected outpatients.

When we start talking phenotypes and interactions with ICS, things get predictably more complicated. One report shows that it's only the noneosinophilic asthma phenotype that's associated with worse outcomes. A small study of well-characterized patients with asthma found that ICS actually reduces COVID-19 gene expression, leading some to postulate that ICS may be protective. This is of course a hypothesis, and the most we can say at this point is that patients with asthma who are using ICSs should continue taking them as prescribed.

Where Does This Leave Us?

Like everything related to COVID-19, we need more data. Until we have them, there are a few things to keep in mind.

First, we need not be afraid of using ICSs for patients who need them. Whether it's harmful, protective, or neither remains unclear, but if your patient has a non–COVID-19 indication for using an ICS, it should be continued. Otherwise, I'm going to continue using common sense and telling people with mild asthma they should be following the same risk mitigation measures as everyone else, but their risk for adverse outcomes probably isn't elevated.

For those with severe disease, I'm advising them to be careful and take extra precautions. This is in keeping with what we think we know at this point.

Aaron B. Holley, MD, is an associate professor of medicine at Uniformed Services University and program director of pulmonary and critical care medicine at Walter Reed National Military Medical Center. He covers a wide range of topics in pulmonary, critical care, and sleep medicine.

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