Introduction: Patients with obstructive lung diseases are possibly at risk of developing severe outcomes of coronavirus disease 2019 (COVID-19). Therefore, the aim of this study was to determine the risk of severe outcomes of COVID-19 among patients with asthma and COPD.

Methods: We performed a nationwide cohort study of patients with COVID-19 from 1 February to 10 July 2020. All patients with COVID-19 registered in the Danish registers were included. Using International Classification of Diseases (ICD) codes and medication history, patients were divided into asthma, COPD or no asthma or COPD. Primary outcome was a combined outcome of severe COVID-19, intensive care or death.

Results: Out of 5104 patients with COVID-19 (median age 54.8 years (25-75th percentile 40.5 to 72.3); women, 53.0%), 354 had asthma and 432 COPD. The standardised absolute risk of the combined end-point was 21.2% (95% CI 18.8-23.6) in patients with COPD, 18.5% (95% CI 14.3-22.7) in patients with asthma and 17.2% (95% CI 16.1-18.3) in patients with no asthma or COPD. Patients with COPD had a slightly increased risk of the combined end-point compared with patients without asthma or COPD (risk difference 4.0%; 95% CI 1.3-6.6; p=0.003). In age standardised analyses, there were no differences between the disease groups. Low blood eosinophil counts (<0.3×109 cells·L-1) were associated with increased risk of severe outcomes among patients with COPD.

Conclusion: Patients with COPD have a slightly increased risk of developing severe outcomes of COVID-19 compared with patients without obstructive lung diseases. However, in age-standardised analysis, the risk difference disappears.