Grayson agrees with Khurana that in the early days of the COVID-19 pandemic, there was much concern that asthma could be a risk factor — a reasonable suspicion, given that the coronavirus attacks the lungs.
But everything that came out of the initial epidemic in China suggested that asthma was not a risk factor for life-threatening COVID, Grayson said, and the data continued to confirm that as the coronavirus spread across the globe.
“It’s not there in the data. If it is there, it’s extremely small risk. It’s nothing I can see,” he said.
Researchers have speculated that people with allergy-driven asthma might have some protection against COVID, due to the way the coronavirus infects the body.
The SARS-CoV-2 virus that causes COVID-19 enters lung cells by engaging with a type of protein on their surface called an ACE2 receptor, Khurana said.
“In the setting of an allergic type of inflammation, the expression of the ACE2 receptor appears to be downregulated. It appears to be lower. There’s not as much receptor,” she said.
Because there aren’t as many ACE2 receptors available, people with allergic asthma might not be as vulnerable to severe infection, Khurana said. This theory also could help explain why other chronic diseases appear to increase COVID risk, she added.
“Patients in conditions like diabetes or hypertension, this receptor expression is increased,” Khurana said. “That’s a possible reason why those comorbid diseases are at especially high risk for this infection.”
But that only explains why allergic asthma isn’t a major risk factor for severe COVID, Grayson said. It doesn’t explain why some studies are finding increased risk among people with non-allergic asthma.
Grayson suspects that the purported link between non-allergic asthma and COVID found in these studies is actually a link between a COVID and a host of different lung ailments, especially COPD.
“There are studies showing that COPD increases your risk of more severe COVID, not markedly but a little bit, not to the extent of things like hypertension and diabetes and [being] elderly,” he said. “I’m concerned that what they’re calling non-allergic asthma actually is COPD, which would skew their data.”