What are the causes of chronic cough?

Common Causes of Chronic Cough

The most common causes of chronic cough are upper airway cough syndrome (UACS) due to rhinosinus conditions, asthma, gastroesophageal reflux disease (GERD), and nonasthmatic eosinophilic bronchitis (NAEB), which together account for over 90% of cases in patients with normal chest radiographs who are nonsmokers and not taking ACE inhibitors. 1

Primary Etiologies

Common Causes

• UACS (formerly called postnasal drip syndrome) - accounts for a significant percentage of chronic cough cases across multiple studies 1
• Asthma - including cough variant asthma, which may present with cough as the sole symptom 1
• GERD - can present as "silent GERD" with cough as the only symptom in up to 75% of cases 2
• Nonasthmatic eosinophilic bronchitis (NAEB) - characterized by cough, eosinophilic infiltration, normal spirometry, and lack of bronchial hyperresponsiveness 1

Medication-Related Causes

• ACE inhibitors - a well-established cause of chronic cough that can develop at any time during treatment 2, 3
• Angiotensin receptor blockers (ARBs) - less commonly associated with cough than ACE inhibitors 3
• Other medications such as omeprazole and leflunomide have been reported to cause cough in some cases 3

Smoking and Environmental Causes

• Cigarette smoking - one of the most common causes of persistent cough in a dose-related manner 2
• Environmental irritants - including dust, allergens, and occupational exposures 2, 4
• Chronic bronchitis/COPD - often associated with smoking history 1

Post-Infectious Causes

• Post-infectious cough - may persist for weeks after an acute respiratory infection 1, 5
• Bordetella pertussis infection - can cause prolonged cough and should be considered in appropriate clinical settings 1, 6

Less Common Causes

• Bronchiectasis from various causes 1
• Interstitial lung diseases 1
• Endobronchial abnormalities (tumors, tuberculosis, sarcoidosis) 1
• Congestive heart failure 1
• Thyroid disease 1
• Habitual or psychogenic cough 1
• Neuromuscular disorders 1
• Mediastinal masses 1
• Obstructive sleep apnea 7

Diagnostic Considerations

Key Clinical Pearls

• Each of the common causes may present with cough as the only symptom without other classic manifestations (e.g., "silent GERD," "cough variant asthma") 1
• The character, timing, or presence/absence of sputum production in cough is not diagnostically valuable 1
• Multiple causes often coexist - in up to 25% of patients, more than one disorder contributes to chronic cough 4
• Women, particularly middle-aged women, have a higher prevalence of chronic cough and more sensitive cough reflex 2

Important Diagnostic Pitfalls

• Assuming absence of typical symptoms rules out a diagnosis (e.g., absence of heartburn doesn't rule out GERD as cause of cough) 2
• Failing to consider NAEB early in the diagnostic evaluation - prevalence ranges from 13-33% in studies outside the United States 1
• Overlooking medication causes, particularly ACE inhibitors, which can trigger cough even after long-term use 2, 3
• Not recognizing that smoking cessation initially leads to a short-term increase in cough reflex sensitivity before improvement 2

Diagnostic Approach

• Focus initial evaluation on detecting UACS, asthma, GERD, and NAEB in patients with normal chest radiographs who are nonsmokers and not taking ACE inhibitors 1
• Consider medication review, particularly ACE inhibitors, as an early step in evaluation 3
• Chest radiography should be performed to rule out concerning infectious, inflammatory, and malignant thoracic conditions 7, 5
• For children (where chronic cough is defined as >4 weeks), the most common causes are respiratory tract infections, asthma, and GERD 7, 5
• Consider referral to pulmonologist or otolaryngologist for refractory cases 7

By systematically evaluating for these common causes, the etiology of chronic cough can be identified and effectively treated in the vast majority of patients.