Chronic Cough Causes
Chronic cough (lasting >8 weeks in adults) is caused by upper airway cough syndrome (UACS), asthma, gastroesophageal reflux disease (GERD), and nonasthmatic eosinophilic bronchitis (NAEB) in over 90% of cases, with multiple conditions frequently coexisting in the same patient. 1
The "Big Four" Primary Causes
These four conditions account for the vast majority of chronic cough cases in nonsmokers with normal chest radiographs who are not taking ACE inhibitors:
Upper Airway Cough Syndrome (UACS)
- Most common single cause, accounting for 33-48% of chronic cough cases 2, 1
- Results from rhinosinus conditions causing postnasal drip 2
- Can present with cough as the only symptom without typical nasal or sinus complaints 1
- Often associated with frequent throat clearing or sensation of postnasal drip 3
Asthma (Including Cough-Variant Asthma)
- Accounts for approximately 16-59% of chronic cough cases 2, 1
- May present as "cough-variant asthma" where cough is the sole manifestation without wheezing or dyspnea 1
- Can cause coughing that wakes patients during the night or early morning 3
- Worsened by exercise or exposure to cold air 3
Gastroesophageal Reflux Disease (GERD)
- Responsible for 5-41% of chronic cough cases 4
- "Silent GERD" presents with cough as the only symptom in up to 75% of cases, with no heartburn or typical GI symptoms 1, 4
- Operates through three mechanisms: upper airway irritation, microaspiration/macroaspiration, and esophageal-bronchial reflex 4
- Cough may worsen after meals or when lying down 3, 4
Nonasthmatic Eosinophilic Bronchitis (NAEB)
- Accounts for approximately 5% of chronic cough cases 2
- Characterized by eosinophilic infiltration, normal spirometry, and lack of bronchial hyperresponsiveness 1
- A common diagnostic pitfall is failing to consider NAEB early in evaluation 1
Critical Secondary Causes
ACE Inhibitor-Induced Cough
- Medication history is crucial in diagnosing chronic cough 1
- ACE inhibitors alter cough reflex sensitivity and are a well-established cause 3
- Both ACE inhibitors and sitagliptin should be discontinued to assess if responsible 2
Smoking-Related Chronic Bronchitis/COPD
- Current cigarette smoking is one of the most common causes of persistent cough 1
- Prevalence increases in a dose-related manner with smoking 1, 3
- Should be considered particularly in patients with smoking history 1
- Smoking cessation initially increases cough reflex sensitivity before improvement 3
Environmental and Occupational Exposures
- Must be considered and addressed if present 2
- Includes dust, allergens, and chemical irritants 3
- Geographic exposure to tuberculosis or endemic fungal diseases should be evaluated 1
Multiple Simultaneous Causes Are Common
A critical concept: 61.5% of chronic cough patients have multiple contributing conditions simultaneously 5. The combination of two or even all three dominant etiologies (UACS, asthma, GERD) commonly coexist in the same patient 1. This requires treatment of all identified conditions for resolution 1.
Important Diagnostic Pitfalls to Avoid
- Do not rely on cough characteristics for diagnosis—the character, timing, or presence/absence of sputum production has no diagnostic value 1
- Even significant sputum production doesn't change the differential in nonsmokers 1
- Never assume absence of typical symptoms rules out a diagnosis—absence of heartburn doesn't exclude GERD as the cause 1, 3
- Women, particularly middle-aged women, have higher prevalence and more sensitive cough reflex 1, 3
Essential Historical Red Flags
Immediately evaluate for life-threatening conditions if present 2:
- Hemoptysis 2
- Fever, night sweats, or unintentional weight loss 1
- Past medical history of cancer, tuberculosis, or AIDS 1
- Systemic symptoms suggesting serious underlying disease 1