A review of 150 studies yielded “no clear evidence” that patients with asthma are at increased risk for COVID-19 diagnosis, hospitalization, severity or mortality. “Health agencies such as the CDC and WHO expressed the opinion that patients with asthma were more vulnerable to becoming severely ill with COVID-19, yet formal comprehensive assessments of the medical literature were lacking," Rajiv Dhand, professor of medicine, Wahid T. Hanna MD Endowed Chair of Medicine and associate dean of clinical affairs at the Graduate School of Medicine at the University of Tennessee Health Sciences Center, told Healio. “Patients with asthma were apprehensive about getting severe COVID-19 and wondered whether they should continue to use inhaled corticosteroids, which are the mainstays of asthma treatment.”
Researchers identified 150 worldwide studies from PubMed and medRxiv databases by searching the terms “asthma,” “SARS-CoV-2” and “COVID-19” and cross-referenced citations in studies available in print or online before December 2020. Data on asthma prevalence were collected from studies of patients with COVID-19 and regional health statistics, and researchers compared asthma prevalence among patients with COVID-19 by region, disease severity and mortality.
“At the time we started analyzing data, there were already some reports that showed asthma did not increase the risk of severe COVID-19 outcomes, so our main findings supported these findings. However, some of our analyses suggest that asthma may actually lower risk of severe COVID-19 outcomes, particularly mortality, which is somewhat surprising,” Dhand told Healio. “Our report also highlights the marked variation in asthma prevalence in various regions of the world.” In 63 studies of 351,728 individuals conducted in the U.S., the pooled prevalence of asthma was 11% (95% CI, 9.8-12.3). The pooled prevalence of asthma was 7.6% (95% CI, 6-9.4) in 31 studies of 203,978 individuals conducted in Europe, 1.9% (95% CI, 0.4-4.4) in 11 studies of 4,050 individuals conducted in China and 5.4% (95% CI, 2.3-9.6) in nine studies of 37,938 individuals conducted in South Korea.
To evaluate asthma prevalence by COVID-19 severity, researchers assessed 26 studies and found an asthma prevalence of 10% (95% CI, 8-12.2) among patients hospitalized with COVID-19 and an asthma prevalence of 9.5% (95% CI, 8-11) among patients who were discharged home with COVID-19. Among living patients hospitalized with COVID-19, there were 42 studies with data on asthma prevalence and disease severity, with a prevalence of 8.7% (95% CI, 6.9-10.7) among those with severe COVID-19 and a prevalence of 9.1% (95% CI, 7.8-10.5) among those with non-severe COVID-19. In 1,828,284 patients in 17 studies, asthma prevalence for those who tested positive for SARS-CoV-2 was significantly lower at 7.8% (95% CI, 5.1-11.1) compared with 10.2% (95% CI, 7.5-13.3) among patients who tested negative for COVID-19. Researchers also reported an asthma prevalence of 6.8% (95% CI, 5.7-8) among patients who died from COVID-19 and a prevalence of 8.4% (95% CI, 7.2-9.8) among patients who survived in 43 studies with such data.
The researchers concluded that the findings “could provide some reassurance to people with asthma regarding its potential to increase their risk of severe consequences of COVID-19.” According to Dhand, the effect of type of asthma, whether atopic or non-atopic, on outcomes of COVID-19 should be assessed. “It is important to understand the underlying biological mechanisms by which asthma, or medications taken by people with asthma, may mitigate COVID-19 outcomes,” Dhand said.
Dr. Kenneth Backman from Allergy & Asthma Care comments: "This study supports previous evidence suggesting no increased risk from asthma, and is very reassuring. There has been evidence that uncontrolled asthma may be a risk factor, so it remains important to maintain asthma control with appropriate medications and contact your physician if your asthma is not well controlled."