Prevalence of asthma–COPD overlap syndrome

Epidemiological studies indicate that patients with asthma–chronic obstructive pulmonary disease (COPD) overlap constitute about a third of patients with obstructive airway diseases. However, in daily practice the coexistence of asthma and COPD does not seem to be diagnosed often. What are the possible reasons for this discrepancy?

Jadwiga Wedzicha: I think the reasons that asthma and COPD are not diagnosed as a combined disorder is that physicians probably do not consider that you can have two airways disorders. Asthma is common. COPD is common. In some patients these two disorders will certainly overlap. I think there is guidance now on what type of patients may have asthma–COPD overlap. If there is a history of asthma in childhood, if there is a high blood eosinophil count, that should make you think more of asthma-COPD overlap syndrome.

I think some physicians view asthma and COPD as a continuum of disorders, as well. We normally regard COPD as a smoking-induced disorder. This is probably another reason why asthma is missed in the elderly patients because we assume they have COPD, particularly if there has been a history of smoking.