By Grant M. Gallagher
A research letter published in the Annals of the American Thoracic Society has challenged the assumptions of the US Centers for Disease Control and Prevention (CDC) that people with asthma are at higher risk of severe SARS-CoV-2 infection.
The research was led by Fernando Holguin, MD, MPH, of the Pulmonary Division at the University of Colorado Anschutz Medical Campus.
People living with asthma typically account for more than 20 percent of those hospitalized in the United States during the annual flu season.
For SARS-CoV-2, several notable risk factors for hospitalization have been demonstrated, such as hypertension, diabetes, chronic obstructive pulmonary disease, and obesity.
Amid the Middle East Respiratory Syndrome (MERS) outbreak, there was little evidence that patients with asthma might be at increased risk.
But the overwhelming proportion of people with asthma among patients in several international studies raises questions about asthma as a particular risk factor when it comes to being hospitalized for COVID-19.
The study team examined the prevalence of asthma among patients hospitalized for COVID-19 reported in 15 studies with population asthma prevalence and a 4-year average asthma prevalence in influenza hospitalizations in the United States.
The team further validated the results with a cross-sectional analysis of 436 COVID-19 patients admitted to the University of Colorado Hospital to assess the likelihood of intubation among people with asthma compared to non-asthmatics.
“The proportion of asthmatics among hospitalized COVID-19 patients is relatively similar to the prevalence of asthma in the general population at each study site. This finding is in marked contrast to influenza,” the authors wrote.
“Seasonal coronaviruses generally do not contribute significantly to hospitalizations due to asthma exacerbations, as they primarily cause upper respiratory tract infections. In the case of SARS-CoV (not COVID-19), asthmatics did not appear to be disproportionately affected, although minimal data are available to make this comparison,” the authors added.
During the 2019–2020 influenza season, approximately 24% of people hospitalized with influenza had asthma. This is a much greater burden than the combined prevalence estimate across the 15 COVID-19 studies (6.8%).
“Despite initial concerns about disproportionately high morbidity and mortality for people with asthma, the data presented here and elsewhere show minimal evidence of a clinically significant relationship,” the authors explain.
Why, however, might this be the case?
The authors offer a speculative answer as to why COVID-19 is not associated with higher hospitalization rates among people with asthma: it may depend on the distribution of the ACE2 receptor in the airway epithelium.
ACE2 is the human receptor to which SARS-CoV-2 binds. Diabetes and hypertension are believed to potentially increase ACE2 expression.
On the other hand, the authors theorize that inhaler-mediated corticosteroid administration may decrease ACE2 expression. Patients with asthma and a predominantly allergic phenotype may independently have significantly lower ACE2 expression.
The authors cautioned that more data from a larger sample size is needed and that patients with asthma can still develop severe COVID-19. They may simply not get it as badly or as severely as the rest of us.
From: https://www.contagionlive.com/news/comparing-asthma-complications-covid19-vs-flu