Asthma and coughing
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Asthma and Chronic Cough: Understanding the Connection
Introduction to Asthma and Chronic Cough
Asthma is a prevalent respiratory condition characterized by airway hyperresponsiveness and inflammation, leading to symptoms such as wheezing, breathlessness, chest tightness, and cough. Chronic cough, defined as a cough lasting more than eight weeks, is a common and often troublesome symptom in asthma patients . This article explores the relationship between asthma and chronic cough, including diagnostic challenges, treatment options, and the impact on patients' quality of life.
Cough-Variant Asthma (CVA)
Definition and Diagnosis
Cough-variant asthma (CVA) is a form of asthma where chronic cough is the predominant or sole symptom, without the typical wheezing or breathlessness . Diagnosing CVA can be challenging as physical examinations and spirometry may appear normal. Methacholine challenge testing, which demonstrates bronchial hyperresponsiveness, is often used to confirm the diagnosis. The resolution of cough with antiasthmatic therapy further supports the diagnosis of CVA.
Mechanisms and Pathophysiology
The mechanisms underlying cough in asthma are complex and multifactorial. Research suggests that preservation of bronchodilating and bronchoprotective effects of deep inspirations is a distinguishing feature of CVA. Additionally, heightened cough reflex sensitivity and eosinophilic airway inflammation are implicated in the genesis of cough in asthma.
Treatment Approaches for Asthmatic Cough
Standard Asthma Therapies
The therapeutic approach to managing cough in asthma generally mirrors that of typical asthma. Inhaled corticosteroids are the primary treatment, often followed by leukotriene receptor antagonists and, in some cases, a short course of oral corticosteroids . These treatments help reduce airway inflammation and control symptoms .
Non-Invasive Biomarkers
The role of non-invasive biomarkers, such as induced sputum and fractional exhaled nitric oxide (FeNO), in guiding treatment for chronic cough due to asthma is still under investigation. Current evidence suggests that while these biomarkers are useful in severe asthma, their specific benefit in chronic cough associated with asthma is limited.
Impact of Chronic Cough on Asthma Patients
Disease Burden and Quality of Life
Chronic cough significantly impacts the quality of life and disease control in asthma patients. Studies have shown that patients with asthma and chronic cough experience worse asthma control, increased airway inflammation, and more comorbidities such as psychological dysfunction, rhinitis, and chronic obstructive pulmonary disease (COPD). These patients also report greater work productivity loss and daily activity impairment.
Objective Cough Monitoring
Objective cough frequency monitoring has been shown to correlate with standard measures of asthma control, providing an additional tool for assessing asthma symptoms. However, cough frequency does not correlate with airflow obstruction or airway inflammation, indicating that it represents an independent dimension of asthma control.
Conclusion
Chronic cough is a common and often debilitating symptom in asthma, particularly in cough-variant asthma. Accurate diagnosis and effective management are crucial for improving patient outcomes. Standard asthma therapies, including inhaled corticosteroids and leukotriene receptor antagonists, remain the cornerstone of treatment. Further research is needed to explore the role of non-invasive biomarkers and to develop targeted therapies that address the specific mechanisms underlying cough in asthma. Understanding and addressing chronic cough in asthma patients can lead to better disease control and improved quality of life.
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