Mortality in Asthma-Chronic Obstructive Pulmonary Disease Overlap in the United States

Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) is recognized increasingly as a distinct clinical entity and is associated with higher comorbidities compared with patients with asthma and COPD alone. Little is known about the leading causes of death related to ACO in the US general population, however. Our aim was to define the causes of mortality among patients with ACO compared with asthma and COPD in the US population.

We examined questions using the National Health and Nutrition Examination Survey III database linked to the National Death Index. The data from 4434 participants were stratified into 4 groups, those with asthma, COPD, ACO, and those without any obstructive lung disease. We examined baseline demographics and used multivariate logistic regression to model the impact of demographics, smoking, and self-reported, physician-diagnosed lung disease on mortality generating odds ratios (ORs) and confidence intervals (CIs).

Among 4434 participants, 120 (2.7%), 340 (7.6%), and 126 (2.8%) participants self-reported diagnoses of asthma, COPD, and ACO syndrome, respectively. Patients with COPD were older (69.7 ± 10.9 years) than other groups. Cardiovascular disease, malignancy, and chronic lower respiratory disease were frequent causes of death. The mortality rates for cardiovascular disease and malignancy were not significantly different among respiratory disease categories. Deaths resulting from chronic respiratory disease were higher in the ACO group (OR 4.9, 95% CI 2.5-9.4) and the COPD group (OR 2.9, 95% CI 1.5-5.4) when compared with those without obstructive lung disease (P < 0.0001).

Although cardiovascular- and malignancy-related deaths are common, a higher proportion of mortality in ACO and COPD is attributed to chronic lung disease.