Chronic Cough

Cough is a non-specific reaction to irritation anywhere from the pharynx to the lungs. Chronic cough is defined as one lasting more than 8 weeks. The commonest causes of chronic cough other than smoking in adults are postnasal drip, asthma, and gastro-oesophageal reflux disease.¹ Respiratory tract infections, asthma, and gastro-oesophageal reflux disease are the most common causes of chronic cough in children. Foreign body aspiration should be considered in young children.

• Chronic cough is reported by 10-20% of adults.
• It is more common in females and obese individuals.
• Cough accounts for 10% of respiratory referrals to secondary care.
• Risk factors include atopy and smoking. Cough may be work-related and a thorough occupation history is very important in assessment.

Most cases of troublesome cough reflect the presence of an aggravant (asthma, drugs, environmental, gastrooesophageal reflux, upper airway pathology) in a susceptible individual. The causes of chronic cough include:²

Adults

• Common: asthma, bronchitis, gastro-oesophageal reflux, postnasal drip, smoking and other irritants
• Less common: bronchiectasis, eosinophilic bronchitis, postinfectious, ACE inhibitors
• Uncommon: aspiration, bronchogenic carcinoma, carcinomatosis, irritable larynx, lymphoma, persistent pneumonia, psychogenic cough, pulmonary abscess, sarcoidosis, tuberculosis.

Children

• Common: asthma, gastro-oesophageal reflux disease, upper and lower respiratory tract infection
• Less common: foreign body aspiration (especially young children)
• Uncommon: aspiration, congenital abnormality or disorder, cystic fibrosis, environmental exposures
• immunological disorder, primary ciliary dyskinesia, psychogenic cough, Tourette syndrome, tuberculosis.

• Most patients present with a dry or minimally productive cough. The presence of significant sputum production usually indicates primary lung pathology.
• Post nasal drip: nasal discharge, frequent need to clear throat, mucoid or mucopurulent secretions in posterior pharynx. X-ray of sinuses may show chronic sinusitis.
• Gastro-oesophageal reflux disease: may or may not be associated with heartburn or regurgitation. May respond to PPIs.^3,4
• Asthma: wheezing, reduced pulmonary function tests. Should respond to two weeks of bronchodilators and inhaled steroids. Cough may wake patient during night.
• ACE inhibitor: common side effect and disappears on withdrawal of drug.
• Production of sputum with expectoration in the morning suggests chronic obstructive pulmonary disease.
• Dry cough lasting many weeks may suggest lung cancer. However non productive barking cough lasting for years may be of psychogenic origin.

• Blood tests include full blood count (infection, eosinophilia), ESR/CRP (infection, malignancy, connective tissue disorders).
• Chest X-ray and spirometry are mandatory for patients with chronic cough.⁵ Consider chest x-ray in patients with acute cough to exclude lung cancer for smokers and other patients with 'red-flag' features such as weight loss and fever.
• Bronchial provocation testing should be performed in patients without a clinically obvious aetiology.
• If the cause of chronic cough remains unclear, high-resolution CT scanning of the chest and bronchoscopy may be required. Bronchoscopy should be undertaken in all patients with chronic cough in whom inhalation of a foreign body is suspected.
• Investigations of oesophageal reflux, including endoscopy.
• Investigations of upper respiratory tract and sinus causes, including CT/MRI scan.

• Treat underlying cause.
• Patients with chronic cough should avoid exposure to irritants that can trigger cough.⁵
• Smoking cessation.
• Referral to secondary care for opinion, investigation and management may be required and may require chest physician, ENT specialist, gastroenterologist or paediatrician, depending on individual context.⁵