Prevalence and clinical impact of asthma-COPD overlap in severe asthma

Abstract

Background: Patients with asthma-COPD overlap (ACO) have a greater symptom burden, worse respiratory function, and more frequent exacerbations than those with asthma alone. However, only a few studies have investigated the prevalence and clinical course of ACO in severe asthma. This study aimed to examine the comorbid rate of ACO and its clinical impact on severe asthma.

Methods: We prospectively enrolled 127 patients with severe asthma from 30 hospitals and clinics. Favorable treatment adherence was ensured, and the prevalence of ACO was assessed using the Japanese Respiratory Society ACO criteria. Patients were categorized into two groups, ACO and non-ACO, and their clinical characteristics were compared. The exacerbation rates with a 3-year follow-up and the annual change in FEV₁ with a 5-year follow-up of 105 individuals were evaluated. The exacerbation-free rate was analyzed using the Kaplan-Meier method and the Cox proportional hazards model.

Results: The prevalence of ACO in severe asthma was 31.5 %. Patients with ACO were older, more frequently male, and had a longer duration of asthma than those without. No significant difference was observed in exacerbation rates between the ACO and non-ACO groups (62.2 % vs. 63.2 %, P = 0.91) or the annual change in FEV₁ (−39.2 mL/year vs. -31.2 mL/year, P = 0.11).

Conclusions: The prevalence of ACO in our multicenter cohort study on severe asthma was approximately 30 %. The presence of ACO was not an independent risk for exacerbations or decline in FEV₁.