麻豆传媒

Early in the COVID-19 pandemic, both the CDC and the World Health Organization identified asthma patients as being at high risk for severe disease and hospitalization, but it soon became evident that this may not be the case when study after study showed little or no support for that conclusion.

Now the largest research review published to date provides even stronger evidence that the risk for severe or fatal COVID-19 in asthma patients is similar to that of the general population -- as long as the asthma remains well controlled.

The review of 150 studies conducted throughout the world should provide reassurance to asthma patients, said Rajiv Dhand, MD, of the University of Tennessee Medical Center in Knoxville, discussing his team's study now online in the .

"The message to patients is, if they do get COVID there is no reason to believe their disease will be more severe than anyone else," Dhand told 麻豆传媒. "But it is important that they stay on their asthma meds. It is especially important right now to not let asthma get out of control."

CDC guidance on the subject, , still warns that people with moderate-to-severe asthma may be "at higher risk of getting very sick from COVID-19." Dhand said he would like to see federal health officials revisit that.

"I think the guidance should reflect the research, which has not shown firm evidence of increased risk," he said. "That would be more straightforward and it would help reassure the public."

The nation's largest group of allergists and immunologists did recently weigh in, in an effort to ease the fears of asthma patients: A last month from the American Academy of Allergy, Asthma & Immunology noted that despite the CDC statement that asthma patients may have a greater risk for severe disease if they become sick with COVID-19, "there are no published data to support this determination at this time."

While several isolated studies did suggest that patients with non-allergic asthma may be at greater than normal risk for developing severe COVID-19, the release noted that the patients in these studies may have actually had chronic obstructive pulmonary disease (COPD), which is an established risk factor for severe disease and death in patients with SARS-CoV-2 infection.

"It appears that [misdiagnosed] COPD may be driving the asthma-related risk seen in those studies," said Mitchell H. Grayson, MD, an allergist at Nationwide Children's Hospital in Columbus, Ohio.

Grayson and Dhand agreed that it is not clear why asthma patients appear to have no greater risk for severe COVID-19 than the general population.

Influenza is a well-recognized risk factor for asthma exacerbations and asthma is associated with increased risk for flu complications and worse outcomes. But Grayson said coronaviruses have not typically been associated with worse asthma outcomes. "With the first SARS and MERS outbreaks we didn't see asthma predominance," Grayson told 麻豆传媒.

In their review, Dhand and colleagues speculated about possible biological mechanisms that might explain risk in patients with asthma: "It has been suggested that decreased ACE [angiotensin-converting enzyme] 2 expression may lower risk of COVID-19 severity and mortality in patients with atopic asthma. It has also been suggested that Th2 immune response in patients with asthma may counter the inflammation induced by SARS-CoV-2 infection," the researchers explained.

"Inhaled corticosteroids such as budesonide, or ciclesonide, used by patients with asthma, may reduce the risk of infection or of developing symptoms leading to diagnosis," the team added.

There is also evidence that asthma exacerbations have declined during the COVID-19 pandemic.

A recent study from Boston Children's Hospital showed a steep decline in hospitalizations for asthma exacerbations last spring and summer, dropping as much as 80%. And preliminary from the international Pediatric Asthma in Real Life study also showed big drops in asthma-related hospitalizations among young patients during the early months of the pandemic.

Grayson said that social distancing, mask wearing and other COVID-19 precautions have all greatly reduced viral transmission, and viral transmission triggers asthma exacerbations.

"Flu is way down and respiratory syncytial virus is virtually non-existent right now," he said. "We just aren't seeing it. Wearing a mask and social distancing are wonderful things for preventing respiratory virus of all kinds."

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