How Long Is "Chronic"?
Cough is categorised by duration: acute (<3 weeks, usually infection), subacute (3–8 weeks, often post-infectious), and chronic (>8 weeks). Chronic cough affects 10–20% of adults and is one of the most common reasons for GP visits. Despite seeming complex, three conditions account for ~90% of chronic cough in non-smokers: upper airway cough syndrome (post-nasal drip), asthma/eosinophilic airway disease, and gastro-oesophageal reflux disease (GORD/GERD).
The Big Three
1. Upper Airway Cough Syndrome (Post-Nasal Drip)
Mucus dripping from the nose or sinuses down the back of the throat stimulates the cough reflex. Causes include allergic rhinitis, non-allergic rhinitis, chronic sinusitis, and vasomotor rhinitis. Symptoms include a sensation of mucus at the back of the throat, frequent throat clearing, and nasal congestion. Treatment: intranasal corticosteroids (fluticasone, mometasone) for allergic rhinitis; antihistamines and decongestants for post-nasal drip; antibiotics and nasal irrigation for sinusitis.
2. Cough Variant Asthma and Eosinophilic Bronchitis
Asthma doesn't always present with wheeze — in cough variant asthma, cough is the only or dominant symptom. Cough is often triggered by cold air, exercise, allergen exposure, or respiratory infections. In eosinophilic bronchitis (without the airway hyperresponsiveness of asthma), the trigger is airway eosinophilia. Both respond well to inhaled corticosteroids. Spirometry and, where available, sputum eosinophil count or exhaled nitric oxide (FeNO) testing help confirm the diagnosis.
3. GERD (Gastro-Oesophageal Reflux Disease)
Acid or non-acid reflux can trigger cough without causing heartburn in up to 75% of cases — making the diagnosis easily missed. Reflux reaching the larynx causes microaspiration and directly stimulates the cough reflex. Clues include cough worse after meals, when lying down, or first thing in the morning. A therapeutic trial of a proton pump inhibitor (PPI) for 8 weeks is often both diagnostic and therapeutic, though response can be slow.
Other Causes to Consider
- ACE inhibitor cough — affects 10–15% of people taking ACE inhibitors (lisinopril, ramipril); caused by accumulation of bradykinin in the airway; resolves within 1–4 weeks of stopping the medication. Switching to an ARB (losartan, candesartan) resolves the cough without losing blood pressure benefit.
- Smoking — "smoker's cough" is chronic bronchitis; the most important intervention is smoking cessation
- Lung cancer — new or changed cough in a smoker over 40 requires a chest X-ray
- Heart failure — cough from pulmonary oedema, often worse when lying flat
- Refractory chronic cough — a subset where no cause is found; driven by cough hypersensitivity syndrome, treated with low-dose gabapentin, pregabalin, or speech pathology-based cough suppression therapy
Evaluation
A chest X-ray is recommended for all adults with unexplained chronic cough. If normal, the "empiric stepwise" approach (trialling treatments for the Big Three in sequence) is practical. Spirometry, sinus imaging, and pH-impedance monitoring (to quantify reflux) are used when empiric treatment fails. See your doctor promptly if cough is accompanied by haemoptysis (coughing blood), significant weight loss, or dysphagia.