Background
Recent evidence has established a beneficial effect of systemic corticosteroids for treatment of moderate-to-severe COVID-19.

Objective
To determine if inhaled corticosteroid use is associated with COVID-19 outcomes.

Methods
In a nationwide cohort of hospitalized SARS-CoV-2 test-positive individuals in Denmark, we estimated the 30-day hazard ratio of intensive care unit (ICU) admission or death among users of inhaled corticosteroids (ICS) compared with users of bronchodilators (β2-agonist/muscarinic-antagonists), and non-users of ICS overall, with Cox regression adjusted for age, sex, and other confounders. We repeated these analyses among influenza test-positive patients during 2010–2018.

Results
Among 6267 hospitalized SARS-CoV-2 patients, 614 (9.8%) were admitted to ICU and 677 (10.8%) died within 30 days. ICS use was associated with a hazard ratio of 1.09 (95% CI [CI], 0.67 to 1.79) for ICU admission and 0.78 (95% CI, 0.56 to 1.11) for death compared with bronchodilator use. Compared with no ICS use overall, the hazard ratio of ICU admission or death was 1.17 (95% CI, 0.87–1.59) and 1.02 (95% CI, 0.78–1.32), respectively. Among 10 279 hospitalized influenza patients, of which 951 (9.2%) were admitted to ICU and 1275 (12.4%) died, the hazard ratios were 1.43 (95% CI, 0.89–2.30) and 1.11 (95% CI, 0.85–1.46) for ICU admission, and 0.80 (95% CI, 0.63–1.01) and 1.03 (95% CI, 0.87–1.22) for death compared with bronchodilator use and no ICS use overall, respectively.

Conclusion
Our results do not support an effect of inhaled corticosteroid use on COVID-19 outcomes, however we can only rule out moderate-to-large reduced or increased risks.

Study registration
The study was pre-registered at encepp.eu (EUPAS35897).