Asthma-COPD Overlap: Pathophysiology, Clinical Relevance, and Management

Abstract

Asthma-COPD overlap (ACO) represents a complex clinical entity characterized by persistent airflow limitation with features of both asthma and chronic obstructive pulmonary disease (COPD). This review synthesizes recent research, emphasizing epidemiology, pathophysiological mechanisms, risk stratification, clinical manifestations, diagnostic challenges, therapeutic strategies, and emerging treatment modalities. The article aims to provide clinicians with comprehensive, evidence-based insights to inform optimal patient care and highlights the implications of international guideline recommendations in the management of ACO.

Introduction

Asthma and COPD are traditionally regarded as distinct obstructive airway diseases; however, clinical practice has revealed a significant subset of patients presenting with overlapping features of both, leading to the conceptualization of asthma-COPD overlap (ACO). The recognition and precise characterization of ACO are paramount due to its unique management needs, prognostic implications, and response to therapy. This review distills the latest evidence and guidelines to clarify the definition, burden, mechanisms, and management of ACO for healthcare professionals.

Epidemiology / Disease Burden

ACO affects an estimated 15-25% of individuals with chronic airway disease, with prevalence varying by population, diagnostic criteria, and healthcare setting. Epidemiological data indicate higher morbidity, increased frequency of exacerbations, poorer health-related quality of life, and greater healthcare utilization in ACO compared to asthma or COPD alone. Studies from the Global Initiative for Asthma (GINA) and the Global Initiative for Chronic Obstructive Lung Disease (GOLD) underscore the significant societal and economic burden posed by ACO, necessitating early recognition and tailored intervention.

Pathophysiology

ACO is defined by persistent airflow limitation with overlapping inflammatory, structural, and functional changes characteristic of both asthma and COPD. The underlying pathophysiology includes a variable combination of eosinophilic and neutrophilic airway inflammation, airway remodeling, small airway disease, and parenchymal destruction. Genetic predispositions, such as polymorphisms affecting inflammatory pathways, may interact with environmental exposures to drive disease phenotype. Notably, ACO patients often exhibit heightened airway hyperresponsiveness, increased bronchial reversibility, and persistent symptoms despite optimal therapy.

Risk Factors

Key risk factors for ACO include advanced age, history of atopy or allergic disease, significant tobacco exposure, occupational inhalant exposure, and a family history of asthma or COPD. Early-life respiratory infections, environmental pollution, and genetic susceptibility also contribute to increased risk. The interplay between modifiable and non-modifiable factors underscores the heterogeneity of ACO and the importance of individualized risk assessment.

Clinical Features

Clinically, ACO presents with persistent respiratory symptoms — including chronic cough, wheeze, dyspnea, and sputum production — often with a history suggestive of both asthma (e.g., childhood onset, atopy, variability in symptoms) and COPD (e.g., significant smoking history, progressive symptoms). Exacerbations are more frequent and severe in ACO compared to asthma or COPD alone. The clinical course is characterized by more rapid lung function decline and greater symptom burden, making early identification critical for prognosis and management.

Diagnosis

Diagnosis of ACO is challenging due to the absence of universally accepted criteria. A combination of clinical history, spirometric evidence of persistent airflow limitation (post-bronchodilator FEV1/FVC < 0.7), and features indicative of both asthma (e.g., bronchial reversibility >12% and 200 mL, eosinophilia) and COPD are essential. Biomarkers such as blood eosinophil count, exhaled nitric oxide (FeNO), and sputum cytology may support diagnosis. Imaging studies and exclusion of alternative diagnoses further refine the diagnostic workup.

Treatment & Management

Management of ACO requires a tailored approach, integrating evidence-based strategies for asthma and COPD. Inhaled corticosteroids (ICS) are the cornerstone for patients with eosinophilic inflammation or significant reversibility, while long-acting bronchodilators (LABA, LAMA) are central to symptom control. Smoking cessation, pulmonary rehabilitation, vaccination, and management of comorbidities are universally recommended. Close monitoring is essential due to the higher risk of exacerbations and complications in ACO.

Recent Advances / Emerging Therapies

Recent advancements include the use of biologic agents targeting type 2 inflammation (e.g., anti-IL-5, anti-IgE therapies) in select ACO phenotypes with prominent eosinophilia. Research is ongoing regarding the role of triple inhaler therapy, novel bronchodilators, and targeted anti-inflammatory agents. Precision medicine approaches — leveraging molecular profiling and biomarkers — are expected to refine treatment algorithms and improve patient outcomes in the near future.

Guideline Recommendations

Current international guidelines (GINA/GOLD) recommend individualized, phenotype-driven therapy for ACO, emphasizing the early use of ICS in patients with asthmatic features and careful escalation to combination therapy as needed. Regular assessment of lung function, exacerbation risk, and symptom control is advocated. Guidelines also stress the need for ongoing research and consensus on standardized diagnostic criteria for improved clinical applicability.

Conclusion

ACO constitutes a distinct clinical syndrome with significant implications for morbidity, mortality, and healthcare utilization. A nuanced understanding of its pathophysiology, risk factors, and clinical presentation is essential for accurate diagnosis and optimal management. Advances in biomarker-driven therapy and evolving guideline recommendations are reshaping the therapeutic landscape, offering hope for improved outcomes in this challenging patient population. Continued research and clinical vigilance are imperative to further elucidate disease mechanisms and refine management strategies.