Key Facts

Chronic cough is one of the commonest reasons for GP and respiratory outpatient referral. It is defined as cough lasting >8 weeks. A systematic approach addressing the most common causes is essential, alongside exclusion of serious underlying pathology.

Epidemiology

Chronic cough affects approximately 12% of the general UK population. It is more common in women (2:1). Prevalence increases with age. It significantly impacts quality of life — associated with urinary incontinence (particularly in women), social embarrassment, sleep disturbance, and depression. Annual NHS cost is estimated at >£100 million.

Aetiology

Common causes ("pathogenic triad" — account for >90% in non-smokers with normal CXR):

• Upper airway cough syndrome (UACS)/post-nasal drip: rhinosinusitis, allergic rhinitis
• Asthma/cough-variant asthma/eosinophilic bronchitis
• Gastro-oesophageal reflux disease (GORD)

Other important causes:

• ACE inhibitors (5-35% incidence)
• Smoking/COPD
• Bronchiectasis
• Post-infectious (pertussis, viral)
• TB, lung cancer
• ILD
• Chronic refractory/unexplained cough (cough hypersensitivity syndrome)

Pathophysiology

Cough reflex hypersensitivity is increasingly recognised as the unifying mechanism in chronic cough. Afferent vagal C-fibre and Aδ-fibre sensitisation in the airway lowers the cough threshold, so that normally sub-threshold stimuli (talking, cold air, perfumes) trigger coughing. This "cough hypersensitivity syndrome" may explain why multiple causes often coexist and why empirical treatments targeting individual causes may only partially improve the cough.

Upper Airway Cough Syndrome

• Post-nasal drip sensation, throat clearing, nasal congestion
• Cobblestoned posterior pharynx
• Worse lying flat

Cough-Variant Asthma

• Dry cough, nocturnal predominance, seasonal variation
• Normal spirometry; positive bronchial challenge test
• Family/personal history of atopy

GORD-Related Cough

• Cough worse after meals, lying flat, or with acidic foods
• May have heartburn/regurgitation but can occur without typical reflux symptoms ("silent reflux")

Red Flags

• Haemoptysis (lung cancer, TB, bronchiectasis)
• Weight loss (malignancy, TB)
• Night sweats (TB, lymphoma)
• Persistent voice change (laryngeal pathology, recurrent laryngeal nerve compression)
• Dysphagia (oesophageal/mediastinal pathology)
• Smoker >45 years with new/changed cough (lung cancer screening)
• Systemic symptoms (vasculitis, sarcoidosis)

Bedside

• Detailed history: duration, triggers, timing, medications (ACEi), smoking, occupation, travel
• Examination: ENT (post-nasal drip), chest auscultation, clubbing
• Peak flow diary: 2-week variability assessment
• FeNO: >25 ppb suggests eosinophilic airway inflammation

Bloods

• FBC: eosinophilia (asthma, eosinophilic bronchitis)
• Total IgE: atopy
• CRP/ESR: if infection/inflammation suspected
• Pertussis serology: if post-infectious cough >2 weeks

Imaging

• CXR: first-line — exclude mass, consolidation, effusion, lymphadenopathy
• HRCT: if CXR abnormal, or to diagnose bronchiectasis, ILD
• CT sinuses: if UACS suspected and not responding to empirical treatment

Special Tests

• Spirometry with reversibility: obstructive pattern in asthma/COPD
• Bronchial challenge test (methacholine/histamine): if cough-variant asthma suspected with normal spirometry
• Induced sputum cell count: sputum eosinophilia >3% (eosinophilic bronchitis/asthma)
• 24-hour oesophageal pH/impedance monitoring: gold standard for GORD-related cough
• Bronchoscopy: if haemoptysis, suspected foreign body, or endobronchial lesion

Non-pharmacological

• Stop ACE inhibitor — switch to ARB; cough resolves within 1-4 weeks
• Smoking cessation: essential in smokers
• Speech and language therapy (SLT): cough suppression techniques for chronic refractory cough — evidence from PSALTI trial
• Anti-reflux measures: elevate head of bed, avoid late meals, weight loss, avoid caffeine/alcohol

Pharmacological

• UACS: intranasal corticosteroid (e.g. mometasone 200 mcg daily or fluticasone 100 mcg BD) + oral antihistamine (cetirizine 10 mg OD or loratadine 10 mg OD); trial for 2-4 weeks
• Asthma/eosinophilic bronchitis: ICS trial for 6-8 weeks (e.g. beclometasone 400 mcg BD or budesonide 400 mcg BD); add LABA if incomplete response
• GORD: PPI trial (omeprazole 20 mg BD or lansoprazole 30 mg BD) for 8 weeks
• Post-infectious/pertussis: usually self-limiting; supportive measures
• Chronic refractory cough: low-dose morphine sulfate 5-10 mg BD (evidence from COUGH-1 trial); gabapentin 300-1800 mg/day (may help but side effects limit use); gefapixant 45 mg BD (P2X3 antagonist — COUGH-1/COUGH-2 trials, NICE appraisal pending)

Surgical/Interventional

• Fundoplication: for refractory GORD-related cough with proven acid reflux on pH studies (rarely needed)

Referral Criteria

• Urgent CXR: unexplained cough >3 weeks (especially smoker >40) — NICE NG12
• Respiratory specialist: cough persisting >8 weeks despite empirical treatment of common causes
• ENT: suspected upper airway pathology, voice change
• Gastroenterology: refractory GORD-related cough

Most chronic cough resolves with identification and treatment of the underlying cause(s). ACE inhibitor cough resolves in >95% within 4 weeks of stopping the drug. Asthma-related cough responds to ICS in >70%. GORD-related cough may take 3-6 months of PPI therapy for full resolution. Chronic refractory cough (no identifiable cause despite thorough workup) affects ~15% of chronic cough patients and may persist for years, significantly impacting quality of life.

Systematic Approach to Chronic Cough

Cough Severity Assessment Tools