What Influences COVID-19 Severity in Patients With Asthma?

Patients with asthma hospitalized with COVID-19 in Michigan in 2020 had more severe outcomes after taking certain factors into account, according to a recent study.

What is known and unknown about the relationship between asthma and COVID-19 has been inconsistent during the pandemic. Some prior research has found that individuals with asthma do not have an increased risk for worse COVID-19 outcomes, but a study published this month said that outcomes may appear to be dependent on the type of asthma one has, as well as the factors of sex and age.

The patients with asthma in this single-center study, conducted in Michigan, did have more severe COVID-19, after considering these other factors.

Additional research is needed to fully understand which aspects of the chronic lung disease might be linked with increased risk from the virus, said the authors, who wrote in the Annals of Allergy, Asthma & Immunology that “data suggest that it is premature to conclude that asthma is not associated with an increased risk of poor outcomes with COVID-19.”

Their research compared hospitalized patients with COVID-19 (confirmed through polymerase chain reaction testing) with asthma (n = 183) and without asthma (n = 1319).

To identify asthma severity level, the researchers looked at asthma maintenance medications, Global Initiative for Asthma classification, pulmonary function tests, immunoglobulin E level, and the highest historical absolute eosinophil count to determine if the patient had eosinophilic vs non-eosinophilic asthma.

Primary outcomes included death, mechanical ventilation, intensive care unit (ICU) admission, and how long the patient was hospitalized in either the ICU or the hospital.

Results were adjusted to include demographics, comorbidities, smoking status, and timing of illness in 2020, with the year split from March, 2020 to June 14, 2020, and from June 15, 2020 to December, 2020.

There were 140 encounters in the first half of the year and 127 encounters in the second half.

The median age of patients with asthma was significantly lower (56 years, P < .001) compared with those without asthma (62 years). In addition, most of the patients with asthma were female (65%) compared with those without asthma (41%, P < .001).

There were 104 patients with mild asthma, 29 patients with moderate asthma, and 49 patients with severe asthma. In addition, just over a third (33%) had eosinophilic asthma and 58% had non-eosinophilic asthma.

Unadjusted analyses showed no difference between patients with asthma and patients without asthma in terms of outcomes. There was no statistically significant difference in looking at inhaled corticosteroid use and eosinophilic phenotype.

However, in adjusted analyses, patients with asthma, when compared with those without asthma, were more likely to have:

  • Mechanical ventilation (OR, 1.58; 95% CI, 1.02-2.44; P = .04)
  • ICU admission (OR, 1.58; 95% CI, 1.09-2.29; P = .02)
  • Longer hospital length of stay (risk ratio, 1.30; 95% CI, 1.09-1.55; P < .003),
  • Death (hazard ratio, 1.53; 95% CI, 1.01-2.33; P = .04)

Patients with moderate asthma had worse outcomes than those with mild asthma, with higher odds of:

  • ICU admission (OR, 2.60; 95% CI, 1.03-6.54; P = .04)
  • Longer hospitalizations (RR, 2.01; 95% CI, 1.29-3.14; P < .002)
  • Longer stays in the ICU (RR, 2.02; 95% CI, 1.03-3.95; P < .002)

Patients with severe asthma had shorter hospital stays (RR, 0.80; 95% CI, 0.65-1.00; P < .04).

In addition, patients who were female and of older age also tended to have worse outcomes, in line with what is already known about sex disparities in asthma. But the finding is also the opposite of what has been shown when examining COVID-19 illness alone, where being male is a risk factor for more severe disease or death.

However, the authors noted that since the sample size of patients with moderate asthma was smaller, confidence intervals were larger, making the findings more challenging to interpret.

Noting that their findings differ from other research, the authors said prior studies had smaller sample sizes of patients with asthma, and primary outcomes differed. Larger cohort studies did show longer periods of intubation and worse outcomes, they said.


Ludwig A, Brehm CA, Fung C, et al. Asthma and coronavirus disease 2019–related outcomes in hospitalized patients: a single-center experience. Ann Allergy Asthma Immunol. 2022;129(1);79-87. doi:10.1016/j.anai.2022.03.017.

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