Causes of cough
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Common Causes of Cough: Acute and Chronic Cough Etiology
Cough is a frequent symptom in medical practice and can be classified as acute (lasting less than 3 weeks) or chronic (lasting more than 8 weeks) Chung2008Tajiri2020. The causes of cough vary depending on its duration and underlying conditions.
Acute Cough: Infections and Respiratory Illnesses
The most common cause of acute cough is infection, particularly upper respiratory tract infections such as the common cold, which are often triggered by viruses like rhinovirus Tajiri2020Atkinson2016. In cases where chest X-rays show abnormalities, pneumonia is a leading cause, followed by lung cancer and asthma exacerbations. When chest X-rays are normal, upper respiratory tract infections remain the most frequent cause, with asthma and cough variant asthma also contributing . The mechanism of cough in viral infections may involve physical disruption of the airway lining, increased mucus production, inflammation, and changes in nerve sensitivity, which can prolong cough even after other symptoms resolve .
Chronic Cough: Major Contributing Conditions
Chronic cough, defined as lasting more than 8 weeks in adults, is most commonly caused by a few key conditions. These include:
- Upper Airway Cough Syndrome (UACS), previously known as postnasal drip syndrome, often related to rhinosinusitis Pratter2006Chung2008Palombini1999+3 MORE.
- Asthma and Cough Variant Asthma (CVA), where cough is the main or only symptom Pratter2006Chung2008Palombini1999+3 MORE.
- Nonasthmatic Eosinophilic Bronchitis (NAEB), which presents with chronic cough without the typical features of asthma Pratter2006Chung2008Lai2013+1 MORE.
- Gastroesophageal Reflux Disease (GERD), where acid reflux irritates the airway and triggers cough Pratter2006Chung2008Palombini1999+2 MORE.
These four conditions account for the vast majority of chronic cough cases, both in Western and Asian populations Pratter2006Palombini1999Lai2013+2 MORE. They may occur alone or in combination, and sometimes the only symptom is cough Pratter2006Palombini1999.
Other Common and Contributing Factors
Other causes of chronic cough include:
- Atopic cough, especially in some Asian populations Lai2013Ishiura2024.
- Chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and bronchiectasis, which are less common but important to consider Chung2008Palombini1999Michaudet2017.
- Environmental and Occupational Exposures, such as tobacco smoke, air pollution, and workplace irritants, can also contribute to chronic cough Chung2008Tarlo2016.
- Medication side effects, particularly from angiotensin-converting enzyme (ACE) inhibitors .
Rare Causes of Chronic Cough
While most cases are due to the common causes above, rare causes should be considered if initial treatments fail. These include:
- Protracted bacterial bronchitis
- Somatic cough syndrome
- Diffuse panbronchiolitis
- Obstructive sleep apnea syndrome (OSAS)
- Interstitial lung disease
Specialized tests like high-resolution chest CT or bronchoscopy may be needed to identify these rare causes after common ones are excluded .
Pathophysiology: Why Cough Persists
Chronic cough can be maintained by heightened sensitivity of the cough reflex, changes in airway nerves, and ongoing inflammation or structural changes in the airways. Sometimes, no clear cause is found, leading to a diagnosis of idiopathic cough Chung2008Atkinson2016.
Conclusion
Cough is most often caused by infections in acute cases and by a small group of conditions—UACS, asthma/CVA, NAEB, and GERD—in chronic cases. Environmental exposures, medications, and rare diseases can also play a role. A systematic approach focusing on the most common causes is usually effective, with further investigation reserved for persistent or unexplained cases Pratter2006Chung2008Palombini1999+7 MORE.
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