Causes of Death in Patients with Asthma-Chronic Obstructive Pulmonary Disease Overlap: Is There Any Difference Compared to Asthma?

Patients with asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) show both asthma and COPD features. The mortality rate of ACO is reportedly lower or higher than that of asthma or COPD alone, probably because of differences in diagnostic labeling, cohort size, severity, and mortality rate definition among studies. The cause-specific mortality rate per 1000 person-years is 2.29 to 25.9 for ACO and 1.39 to 11.7 for asthma. The most common causes of mortality are cancer and cardiovascular diseases, and the causes of death in individuals with asthma and ACO are comparable. However, ACO is associated with more comorbidities compared with asthma, and some of these comorbidities affect mortality and cause of death. The impact of coronavirus disease 2019 (COVID-19), which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), on asthma and ACO-related mortality is critical. COPD, but not asthma, has been linked to SARS-CoV-2 infection and its severity, and patients with ACO are more likely to develop severe COVID-19 infection compared with patients with asthma. Thus, comorbidities, including malignant diseases, influence the prognoses of ACO and asthma. Several infectious diseases, including COVID-19, also affect ACO-related mortality. Controlling comorbidities and contagious diseases can improve ACO prognosis.