Comparison of the risk of pneumothorax in COVID-19 and seasonal influenza

Limited evidence exists regarding the link between coronavirus disease 2019 (COVID-19) and pneumothorax. Therefore, we aimed to evaluate the occurrence rate of pneumothorax in hospitalized patients with COVID-19 and compare the risk of pneumothorax between patients with COVID-19 and influenza. This retrospective cohort study used patient data from the National Health Insurance Service of South Korea. Patients diagnosed with COVID-19 (December 2019 to December 2021) and influenza (January 2019 to December 2021) who required hospitalization and respiratory support were included. We identified 46,460 patients with COVID-19 and 6,117 with influenza. The occurrence rate of pneumothorax was 0.74% in patients with COVID-19. In an inverse probability of treatment weighting matched cohort, the Cox proportional hazards regression model showed that COVID-19 was not associated with an increased risk of pneumothorax compared to influenza (hazard ratio, 1.22; 95% confidence interval, 0.75-1.99). However, the risk of pneumothorax associated with COVID-19 compared to influenza was significantly higher in patients without chronic lung disease than in those with (P for heterogeneity = 0.037). In conclusion, COVID-19, compared with influenza, is not associated with an increased risk of pneumothorax; however, it is associated with an increased risk in patients without chronic lung disease.