What is chronic cough?

A chronic cough is a cough that lasts for more than 8 weeks in adults and 4 weeks in children.  It is important to note that chronic cough is not a condition but a symptoms of other conditions.  The most common cause of chronic cough is cigarette smoking, asthma, chronic obstructive pulmonary disease (COPD), acid reflux and postnasal drip.  Coughing from time to time helps to clear secretions and particles but also helps to prevent infections.  A chronic cough may not be the sign of a serious problem but it can affect your sleep, make you feel dizzy, be embarrassing and even cause rib fractures. 

Among people who smoke cigarettes, chronic cough is more common in men.  In people ages below 70 years, chronic cough is more common in women. The risk of developing chronic cough increases with age and peaks in the 8^th decade. 

What are the causes of chronic cough?

The causes of chronic cough include:

• Asthma: Asthma is the leading cause of chronic cough in children and the second most common cause of chronic cough in adults.  Other signs and symptoms which may accompany the chronic cough are shortness of breath and wheezing.  Thee asthma-related cough may follow an upper respiratory infection, be seasonal or exacerbate with exposure to dry air, cold or fumes.

• Postnasal drip: Postnasal drip occurs when secretions from your nose flow into the back of your throat which can irritate the throat, triggering a cough.  Sinusitis (inflammation or infection of the sinuses), rhinitis (inflammation of the mucous membranes inside your nose and is also known as coryza), colds and allergies can all contribute to the development of postnasal drip.  Signs and symptoms of postnasal drip include a sensation of fluids in the back of the throat which makes you feel like you need to clear your throat frequently and a runny nose.
• Acid reflux: Acid reflux is also known as gastroesophageal reflux and occur when your stomach acid flows back into your esophagus- the tube connecting your stomach to your throat, though which food reaches your stomach- and throat.  This acid may cause inflammation of the tissues in your throat which will lead to coughing and this condition is known as gastroesophageal reflux disease (GERD).  GERD may cause you to have a sour taste in your mouth and heartburn.

Asthma, postnasal drip and acid reflux account for up to 90% if all cases of chronic.  Other causes of chronic cough include:

• Respiratory tract infection: A cold may cause a cough which lasts for more than 8 weeks due to postnasal drip or irritability of the airways due to the infection.  Following a viral upper respiratory infection, bacterial sinusitis or bacterial tracheobronchitis - inflammation of the trachea (windpipe) and bronchi (respiratory tracts in the lungs) - can develop resulting in a cough that produces a yellow to dark green sputum (phlegm).

• Use of Angiotensin Converting Enzyme (ACE) inhibitors: ACE inhibitors can cause a chronic cough that is usually dry and hacking in 20% of people.  This medication is usually used to treat high blood pressure.
• Lung cancer: Very few people with chronic cough have lung cancer.  It should be suspected in people who are past smokers, begin to cough up blood and whose cough has changed suddenly.
• Chronic bronchitis: This condition mainly affects current or past smokers.  It causes a chronic cough due to irritation of the airways.  Sometimes, there may be the presence of sputum upon coughing.

What are the signs and symptoms associated with chronic cough?

The signs and symptoms that may be associated with chronic cough depend on the underlying cause. Some of these symptoms may include:

• Runny nose.
• Postnasal drip- the feeling of liquid running down the back of your throat.
• Hoarseness of voice.
• Sore throat.
• Shortness of breath and wheezing.
• Sour taste in mouth or heartburn.
• Coughing up blood (rarely).

Making a diagnosis

To make a diagnosis, your doctor take a detailed history from you to know more about your symptoms.  After the history taking, your doctor will perform a thorough physical examination to look for signs associated with the chronic cough.  After the history and physical examination, your doctor may initiate a trial of treatment before any other tests are performed.  If your condition improves, no other tests are required.  However, if your condition does not improve or the diagnosis is not clear, then your doctor will order some tests to make a diagnosis and these include:

• Laboratory test: If the sputum you cough up is coloured, a sample of it may be taken to test for which bacteria is causing the infection in order for your doctor to know which antibiotics can be used to kill the bacteria effectively.
• Lung function tests: A simple and noninvasive test called spirometry can be used to diagnose COPD or asthma.  This test measures how much air can your lungs hold and how fast can you remove air from your lungs.
• Lung imaging: If you are a past or current smoker, or you have other lung conditions, a chest x-ray or even a computed tomography (CT) scan of the chest may be done.
• Bronchoscopy: If your doctor finds an abnormality on imaging, he/she may perform a bronchoscopy to have direct visualisation of the inside of your lungs and to be able to take a few samples which will be sent to the laboratory to be examined under the microscope.  This procedure involves your doctor passing a thin and flexible tube, containing a camera at its end, into your mouth to reach your lungs.

What are the treatments of chronic cough?

It is of utmost importance to determine the cause of the chronic cough in order to for your doctor to provide an appropriate and effective treatment.  Smokers will be advised to stop smoking and if someone is suffering from chronic cough due to an ACE inhibitor, the medication will be replaced by an alternative.  Medications are that used in the treatment of chronic cough include:

• Inhaled asthma drugs: Inhaled corticosteroids and bronchodilators are the most effective treatment for asthma-related cough.  These drugs help to decrease inflammation and open the airways.
• Decongestants, antihistamines and corticosteroids: These drugs are used to treat allergies and postnasal drip.
• Acid blockers: There are several lifestyle modifications which can be made to help relieve the symptoms associated with acid reflux and these include avoiding eating fat foods, alcohol abuse, eating 2-3 hours before bedtime and cigarette smoking. Elevating the head of the bed by 6-8 inches may be useful as well.  If these lifestyle modifications are not useful, then a class of medications called proton-pump inhibitors (acid blockers) can be used to slow the production of acid in the stomach.  Examples include omeprazole, esomeprazole and lansoprazole.  It may take more than 8 weeks before your cough resolves completely.
• Antibiotics: If the chronic cough is due to a bacterial infection, your doctor will prescribe antibiotics to kill the bacteria.
• Cough suppressants: These medications often comes in the form of syrups which may relieve your cough.

What are the complications of chronic cough?

Chronic cough can lead to complications such as:

• Fractured ribs
• Loss of consciousness

• Inadequate sleep
• Vomiting
• Headache
• Leakage of urine during coughing
• Light-headedness

J. Alastair, I. and Simon, M., 2016. Davidson's Essentials of Medicine. 2nd ed. London: ELSEVIER.

Parveen, K. and Michael, C., 2017. Kumar & Clarks Clinical Medicine. 9th ed. The Netherlands: ELSEVIER.