Chronic obstructive asthma
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Chronic Obstructive Asthma: Understanding the Overlap
Introduction to Chronic Obstructive Asthma
Chronic obstructive asthma, often referred to as asthma-COPD overlap (ACO), represents a subgroup of patients who exhibit characteristics of both asthma and chronic obstructive pulmonary disease (COPD). This condition is particularly challenging to diagnose and manage due to the overlapping symptoms and pathophysiological features of both diseases .
Prevalence and Global Impact
Asthma and COPD are prevalent chronic respiratory diseases worldwide, with significant morbidity and mortality. In 2015, asthma was the most prevalent chronic respiratory disease, affecting twice as many individuals as COPD. However, COPD accounted for a higher number of deaths, being eight times more common than deaths from asthma. The prevalence of asthma increased by 12.6% from 1990 to 2015, while COPD prevalence increased by 44.2% during the same period.
Defining Asthma-COPD Overlap (ACO)
Asthma-COPD overlap (ACO) is characterized by persistent airflow obstruction in patients with asthma or variable airflow limitation in patients with COPD. This overlap is more common in older adults and smokers, making it difficult to distinguish between the two conditions . The term ACO is used to describe patients with features of both diseases, but there is no consensus on a precise definition, leading to variability in research findings .
Pathophysiology and Immunology
Both asthma and COPD involve chronic inflammation of the respiratory tract, but the type of inflammation differs. Asthma is typically associated with eosinophilic inflammation, while COPD is linked to neutrophilic inflammation . In ACO, patients may exhibit a combination of these inflammatory profiles, complicating the diagnosis and treatment . The involvement of T helper type 2 (Th2) cells and their associated cytokines is significant in both diseases, suggesting a potential overlap in the underlying immunological mechanisms .
Clinical Features and Diagnosis
Patients with ACO often present with symptoms such as wheezing, cough, and dyspnea, which are common to both asthma and COPD. However, the presence of fixed airflow limitation, hyperresponsiveness, and a history of smoking are critical factors in diagnosing ACO . The use of biomarkers, such as eosinophil counts and specific gene expression profiles, can aid in identifying patients with ACO and tailoring appropriate treatments.
Treatment and Management
Managing ACO requires a comprehensive approach that addresses both asthma and COPD components. Inhaled corticosteroids are commonly used to control inflammation, particularly in patients with eosinophilic inflammation . Bronchodilators, such as long-acting beta-agonists (LABAs) and long-acting muscarinic antagonists (LAMAs), are also essential in managing airflow obstruction. Personalized treatment plans based on the patient's specific inflammatory profile and clinical features are crucial for effective management .
Conclusion
Chronic obstructive asthma, or asthma-COPD overlap, is a complex condition that requires careful diagnosis and management. Understanding the overlapping features and distinct characteristics of asthma and COPD is essential for developing effective treatment strategies. Ongoing research is needed to refine the definitions, identify biomarkers, and improve therapeutic options for patients with ACO.
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