Chronic cough is defined as a cough that persists for more than eight weeks. This condition affects approximately 10% of the adult population. Chronic cough is important because it can significantly impact the quality of life, lead to complications such as sleep disruption, and indicate underlying health issues that require medical attention.
The cough reflex
A cough is a protective reflex that clears the airways of irritants, mucus, and pathogens. It involves the respiratory system, including the lungs, airways, and muscles of respiration, as well as the nervous system. Coughing is triggered by the activation of sensory nerves in the airway, which send signals to the brainstem. The brain then coordinates a response that results in a forceful expulsion of air from the lungs. This reflex is crucial for maintaining airway patency and preventing respiratory infections.
What is the most common cause of chronic cough in adults?
Does the patient smoke or have a history of smoking?
Assessing chronic cough differs between smokers and non-smokers due to the impact of cigarette smoking on the lungs. Smoking causes significant damage to the respiratory system, leading to inflammation, irritation, and structural changes in the airways. This damage can result in chronic bronchitis and other smoking-related lung diseases, making the evaluation of smokers focus on identifying these specific issues. In contrast, non-smokers are more likely to have chronic coughs caused by factors unrelated to smoking, such as allergies, infections, or other non-smoking-related conditions. This distinction guides the diagnostic approach, with an emphasis on evaluating the extent of lung damage in smokers and exploring other common causes in non-smokers.
Non-smokers: Postnasal drip syndrome (PNDS)
The most common cause of chronic cough in adults without a history of smoking is postnasal drip syndrome (PNDS), also known as upper airway cough syndrome. This condition occurs when excess mucus from the nasal passages drips down the back of the throat, irritating the cough receptors. PNDS can result from allergic rhinitis, sinusitis, or non-allergic rhinitis. Patients typically present with symptoms such as a sensation of mucus in the throat, frequent throat clearing, and a persistent cough. Diagnosis is often based on clinical history and physical examination, and treatment includes addressing the underlying cause, such as using antihistamines for allergic rhinitis or antibiotics for bacterial sinusitis.
Smokers (or ex-smokers): Chronic obstructive pulmonary disease (COPD)
In adults with a history of smoking, the most common cause of chronic cough is chronic obstructive pulmonary disease (COPD). Persistent respiratory symptoms and airflow limitation characterize COPD due to airway and alveolar abnormalities, usually caused by significant exposure to noxious particles or gases. It commonly presents in individuals over the age of 40 with a history of smoking. Symptoms include chronic cough, sputum production, and dyspnea. Diagnosis is confirmed by spirometry showing airflow limitation that is not fully reversible. Management includes smoking cessation, bronchodilators, and corticosteroids.
Other common medical conditions associated with chronic cough
Viral infections
Certain viral infections can lead to chronic cough, particularly when the initial infection causes long-lasting irritation and inflammation of the airways. Common examples include respiratory syncytial virus (RSV), adenovirus, and influenza virus. Symptoms typically include a persistent cough that lingers after the acute phase of the infection has resolved, along with fatigue and mild respiratory symptoms. Diagnosis is usually clinical, based on the history of a recent viral infection. Treatment focuses on supportive care, hydration, and sometimes the use of bronchodilators or corticosteroids to reduce airway inflammation.
Gastroesophageal reflux disease (GERD)
GERD is when stomach acid frequently flows back into the esophagus, irritating the lining. It can cause a chronic cough by stimulating the cough reflex. Typical symptoms include heartburn, regurgitation, and a sour taste in the mouth. Diagnosis is based on clinical symptoms and may be confirmed with pH monitoring. Treatment includes lifestyle modifications and proton pump inhibitors.
Asthma
Asthma is a chronic inflammatory disorder of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. It often presents in childhood but can develop at any age. Symptoms include wheezing, shortness of breath, chest tightness, and cough, especially at night or early morning. Pulmonary function tests support the diagnosis. Treatment involves inhaled corticosteroids and bronchodilators.
Medication-induced cough
Certain medications, particularly angiotensin-converting enzyme (ACE) inhibitors, can cause a chronic cough as a side effect. This cough is typically dry and non-productive. Diagnosis is made by reviewing the patient’s medication history and discontinuing the offending drug. The cough usually resolves within weeks of stopping the medication.
Chronic bronchitis
Chronic bronchitis, a type of COPD, involves inflammation of the bronchial tubes with mucus production, leading to a persistent cough. It usually affects older adults with a history of smoking. Symptoms include a productive cough lasting at least three months for two consecutive years. Diagnosis is clinical, and treatment includes smoking cessation and bronchodilators.
Non-asthmatic eosinophilic bronchitis (NAEB)
NAEB is characterized by chronic cough and sputum eosinophilia without the airway hyperresponsiveness seen in asthma. It presents similarly to asthma but without wheezing or airflow obstruction. Diagnosis requires sputum analysis showing elevated eosinophils. Treatment includes inhaled corticosteroids.
Bronchiectasis
Bronchiectasis involves permanent enlargement of parts of the lung’s airways, leading to frequent infections and chronic cough with sputum production. It can occur at any age but is more common in older adults. Symptoms include chronic cough, large amounts of sputum, and recurrent respiratory infections. A high-resolution CT scan confirms the diagnosis. Treatment includes airway clearance techniques and antibiotics for infections.
Interstitial lung disease (ILD)
ILD encompasses a group of lung disorders causing progressive scarring of lung tissue. Symptoms include a dry cough and shortness of breath. It commonly affects middle-aged and older adults. Diagnosis involves imaging studies like high-resolution CT scans and lung biopsies. Treatment focuses on managing symptoms and slowing disease progression with medications like corticosteroids and antifibrotics.
Tuberculosis (TB)
TB is a bacterial infection caused by Mycobacterium tuberculosis. It primarily affects the lungs and can cause a chronic cough with sputum production, sometimes blood-tinged. TB is more common in immunocompromised individuals and those living in or traveling to areas with high TB prevalence. Diagnosis involves sputum analysis and chest X-ray. Treatment includes a prolonged course of antibiotics.
Lung cancer
Chronic cough can be an early symptom of lung cancer, especially in smokers. Other symptoms may include hemoptysis, weight loss, and chest pain. Diagnosis involves imaging studies like CT scans and biopsy of suspicious lesions. Treatment depends on the type and stage of cancer and may include surgery, chemotherapy, and radiation therapy.
Less common but important medical conditions associated with chronic cough
Heart failure
Heart failure can cause chronic cough due to fluid accumulation in the lungs. Symptoms include dyspnea, orthopnea, and leg swelling. Diagnosis involves clinical assessment, echocardiography, and BNP levels. Management includes lifestyle modifications and medications like diuretics and ACE inhibitors.
Pulmonary fibrosis
Pulmonary fibrosis involves progressive scarring of the lung tissue, leading to chronic cough and breathlessness. It typically affects older adults. High-resolution CT scans and lung biopsy confirm the diagnosis. Treatment focuses on symptom management and slowing disease progression with medications like antifibrotics.
Sarcoidosis
Sarcoidosis is an inflammatory disease that affects multiple organs, primarily the lungs. It can cause chronic cough, dyspnea, and chest pain. Diagnosis involves clinical assessment, imaging studies, and biopsy showing non-caseating granulomas. Treatment includes corticosteroids to reduce inflammation.
Bronchiolitis obliterans
Also known as obliterative bronchiolitis, this condition involves inflammation and fibrosis of the small airways, leading to chronic cough and shortness of breath. It can result from respiratory infections, inhalation of toxic fumes, or post-lung transplant. A lung biopsy confirms the diagnosis. Treatment includes immunosuppressive medications.
Atypical infections
Infections caused by atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae, or fungi can lead to chronic cough. Symptoms vary depending on the pathogen but often include prolonged cough and systemic symptoms like fever and malaise. Diagnosis involves specific serologic or culture tests. Treatment depends on the pathogen and may include antibiotics or antifungals.
Occupational lung disease
Chronic cough can result from long-term exposure to occupational hazards such as dust, chemicals, or fumes. Conditions include silicosis, asbestosis, and occupational asthma. Diagnosis involves a thorough occupational history and imaging studies. Management includes removing the patient from exposure and symptomatic treatment.
Vocal cord dysfunction
Vocal cord dysfunction involves inappropriate closure of the vocal cords during respiration, causing chronic cough and wheezing. It is often misdiagnosed as asthma. Diagnosis is confirmed by laryngoscopy. Treatment includes speech therapy and breathing techniques.
Chronic hypersensitivity pneumonitis
This condition results from repeated exposure to inhaled antigens, leading to chronic lung inflammation and fibrosis. Symptoms include cough, dyspnea, and fatigue. Diagnosis involves clinical history, imaging studies, and lung biopsy. Management includes avoiding antigen exposure and using corticosteroids.
Pulmonary embolism
Chronic cough can be a symptom of recurrent pulmonary embolism, where blood clots travel to the lungs. Symptoms include sudden onset of dyspnea, chest pain, and hemoptysis. Imaging studies like CT pulmonary angiography confirm the diagnosis. Treatment involves anticoagulation therapy.
Eosinophilic granulomatosis with polyangiitis (EGPA)
EGPA, formerly known as Churg-Strauss syndrome, is a rare autoimmune disease characterized by asthma, eosinophilia, and vasculitis. It can cause chronic cough, sinusitis, and systemic symptoms. Diagnosis involves blood tests showing eosinophilia and biopsy of affected tissues. Treatment includes corticosteroids and immunosuppressive agents.
Other symptoms and signs
- Sputum characteristics: The presence and nature of sputum can provide clues about the underlying cause of a chronic cough. For instance, a productive cough with thick, purulent sputum often indicates a bacterial infection, such as chronic bronchitis or bronchiectasis. In contrast, clear or white sputum may be seen in viral infections or conditions like asthma and GERD. Blood-tinged sputum (hemoptysis) raises concern for more serious conditions such as tuberculosis, lung cancer, or a pulmonary embolism. Assessing the color, consistency, and amount of sputum can guide further diagnostic evaluation.
- Hemoptysis: Coughing up blood is a particularly alarming symptom that warrants immediate medical attention. Hemoptysis can be caused by several conditions, including tuberculosis, lung cancer, bronchiectasis, and pulmonary embolism. The volume and frequency of blood expectoration can provide additional diagnostic clues. For example, massive hemoptysis is more likely associated with bronchiectasis or lung cancer, while small amounts of blood mixed with sputum might be seen in bronchitis or tuberculosis. Prompt evaluation with imaging studies and possibly bronchoscopy is essential to determine the cause and initiate appropriate treatment.
- Wheezing: Wheezing is a high-pitched whistling sound produced during breathing, typically indicating airway obstruction or narrowing. It is commonly associated with asthma and COPD but can also occur in other conditions like bronchiectasis and VCD. The presence of wheezing, especially if accompanied by shortness of breath, suggests an obstructive airway disease. Spirometry and other pulmonary function tests are useful in diagnosing and differentiating these conditions.
- Chest pain: Chest pain accompanying a chronic cough can point to various underlying conditions. Pleuritic chest pain, which worsens with deep breathing or coughing, may indicate pleurisy, pulmonary embolism, or pneumonia. Central chest pain that radiates to the back or shoulders could be a sign of aortic dissection or esophageal conditions like GERD. Persistent or severe chest pain, particularly if associated with other symptoms like shortness of breath or hemoptysis, should prompt urgent medical evaluation to rule out serious conditions.
- Dyspnea: Shortness of breath, or dyspnea, is a common symptom associated with chronic cough and can indicate conditions affecting the respiratory or cardiovascular systems. Dyspnea at rest or with minimal exertion may suggest heart failure, COPD, or pulmonary fibrosis. Orthopnea (difficulty breathing when lying flat) and paroxysmal nocturnal dyspnea (sudden episodes of breathlessness at night) are classic signs of heart failure. Comprehensive assessment, including imaging and cardiac evaluation, is necessary to determine the cause and guide treatment.
- Weight loss: Unintentional weight loss is a concerning symptom that often indicates a more serious underlying condition, such as cancer, chronic infection (e.g., tuberculosis), or severe chronic disease (e.g., COPD or pulmonary fibrosis). In the context of chronic cough, significant weight loss should prompt evaluation for malignancies like lung cancer, which commonly presents with cough, weight loss, and other systemic symptoms. Detailed history, physical examination, and appropriate imaging studies are critical in diagnosing the cause.
- Night sweats: Night sweats, particularly if they are drenching and recurrent, can be associated with infections like tuberculosis, malignancies like lymphoma, or other systemic diseases. When coupled with chronic cough, night sweats raise suspicion for infectious or neoplastic processes. Further investigation with imaging, laboratory tests, and possibly biopsy may be required to identify the underlying cause.
- Fever: Persistent or recurrent fever in an adult with chronic cough suggests an infectious etiology, such as pneumonia, tuberculosis, or bronchiectasis. Fever patterns can sometimes provide diagnostic clues; for instance, intermittent fever with night sweats and weight loss may indicate tuberculosis, while a high, sustained fever could be seen in bacterial pneumonia. Blood tests, sputum cultures, and imaging studies are useful in diagnosing infectious causes of chronic cough.
- Fatigue: Chronic cough can be exhausting, leading to persistent fatigue. Fatigue itself is a non-specific symptom but, when associated with other symptoms like dyspnea, weight loss, and night sweats, it can point to systemic conditions such as cancer, chronic infection, or significant chronic lung disease. Evaluating the overall clinical picture and conducting relevant investigations can help determine the cause of fatigue in the context of chronic cough.
Advice for patients
Adults with chronic cough should see a doctor if the cough persists for more than eight weeks and is accompanied by alarming symptoms such as hemoptysis, unexplained weight loss, severe breathlessness, night sweats, or fever. Chronic cough can indicate various underlying conditions, some of which may be serious and require prompt medical attention. The appropriate treatment and management depend on the underlying cause identified by the healthcare provider.
For common conditions like postnasal drip syndrome or GERD, treatment may include medications such as antihistamines, decongestants, nasal corticosteroids, or proton pump inhibitors. For chronic bronchitis or COPD, smoking cessation, bronchodilators, and inhaled corticosteroids may be recommended. Patients should follow medical advice, complete prescribed treatments, and attend follow-up appointments to manage their condition effectively. If symptoms worsen or new symptoms develop, they should seek medical care promptly.
Summary
Chronic cough in adults is a persistent cough lasting more than eight weeks, affecting a significant portion of the population. It can indicate various underlying conditions, ranging from common issues like postnasal drip syndrome and COPD to less common but serious diseases like pulmonary fibrosis and lung cancer. Understanding the cough reflex, identifying the most common causes based on smoking history, and recognizing other associated medical conditions are crucial for diagnosis and management. Patients with chronic cough should seek medical evaluation to determine the underlying cause and receive appropriate treatment.
References
British Thoracic Society Clinical Statement on Chronic Cough in Adults:
- Morice AH, Millqvist E, Bieksiene K, et al. British Thoracic Society Clinical Statement on chronic cough in adults. Thorax. 2023;78(Suppl 6). doi:10.1136/thorax-2023-220087.
Chronic Cough: New Insights and Future Prospects:
- Song WJ, Chang YS, Faruqi S, et al. Chronic cough: new insights and future prospects. Eur Respir Rev. 2023;32(167):220211. doi:10.1183/16000617.0211-2022.
Chronic Cough: More Than Just a Persistent Cough:
- Satia I, Badri H, Woodhead M, et al. Chronic cough: more than just a persistent cough: a systematic literature review to understand the impact of chronic cough on quality of life. Qual Life Res. 2023;32(3):505-516. doi:10.1007/s11136-022-03284-6.
The Therapeutic Landscape in Chronic Cough:
- Mazzone SB, Smith JA, McGarvey L, et al. The therapeutic landscape in chronic cough. Lung. 2023;201(1):21-33. doi:10.1007/s00408-022-00503-w.