Causes of Chronic Cough
I see many patients with a chronic cough. Often they are referrals for a second or third opinion from other specialists. It is a problem that can be seriously debilitating, and significantly impact on quality of life. In this article, I'll be discussing what a chronic cough is, symptoms associated with a chronic cough and what causes it. The treatment of a chronic cough depends treating the underlying cause. In 75-90% of cases of a chronic cough, it is possible to identify the cause, however, in some cases, the cause remains unknown. However, there are still treatments that can be administered in these cases.
What is a chronic cough?
A chronic cough is a cough that has lasted for more than 8 weeks. A chronic cough can be 'dry' or 'wet'. Depending on the cause of a chronic cough, there are sometimes associated symptoms. Associated symptoms include: mucus running down the back of the nose ('post-nasal drip or discharge'), throat-clearing, shortness of breath, sinusitis, indigestion or heartburn, a husky or hoarse voice, bitter tasting fluid in the mouth ('waterbrash') and occasionally coughing up blood ('haemoptysis')
One common symptom that can occur regardless of the cause are choking episodes. The medical term for this is laryngospasm, and it can be one of the most frightening aspects of a chronic cough. It occurs when the vocal cords temporarily snap shut, which means that you can't breathe until they relax and open again. The vocal cords will open again, but until they do, patients often report a sensation of panic and sometimes even a fear that they are going to die.
Having a chronic cough can be a debilitating condition and give rise to other problems such as incontinence, fainting episodes ("cough syncope"), disturbed sleep, excessive sweating, and headaches. People have even fractured ribs in severe cases.
Is it serious?
Usually not, however, anyone who has a cough for more than three weeks should as a minimum have a chest x-ray to investigate the possibility of more serious causes of a cough, such as lung cancer.
What causes a chronic cough?
There are very many causes of a cough. It is not uncommon for patients to have a combination of problems that give rise to a common cough. Common causes include:
Laryngopharyngeal ("silent") reflux
Laryngopharyngeal reflux (LPR) occurs when the contents of the stomach goes back up the gullet to the back of the throat (sometimes it can go all of the way to the back of the nose). LPR can cause a variety of symptoms, such as a sensation of a lump in the throat ("globus pharyngeus"), a husky voice, sore throat, persistent throat-clearing, throat irritation, mucus at the back of the nose (post nasal drip), laryngospasm and a chronic cough. I have a particular interest in LPR and sit on the regional reflux multidisciplinary team (MDT). There are three main ways of treating LPR: lifestyle changes; medication; and occasionally surgery. I will be publishing a more detailed article on LPR shortly.
Post-nasal drip or discharge is then the sensation of mucus dripping down the back of the nose into the throat. It can be caused by problems with the nose or sinuses or (as mentioned above) by LPR.
Asthma is the second most common cause of cough in adults and the most common cause in children. It is often, but not always, associated with symptoms of breathlessness and wheezing. Asthma-related cough is sometimes worse at night, and commonly occurs with other allergies.
Respiratory Tract Infections
Infections of the respiratory tract are a common cause of a cough, although usually they are self-limiting and resolve after a week or two. However, both viral and bacterial infections such as 'flu or the common cold can give rise to a chronic cough. One quite common cause of a chronic cough that is often not picked up is pertussis, also known as whooping cough.
This is a problem that is often overlooked. Patients who have pharyngeal hypersensitivity commonly (but not always) give a history of an initial cough or cold, with a subsequent cough that 'never went away'. It is believed that the virus causing the infection causes increased sensitivity of the back of the throat, giving rise to an exaggerated cough reflex. This means that normal stimulation, such as swallowing saliva, can precipitate a cough. The increased sensitivity can also 'unmask' problems such as LPR, that were previously present, but did not cause any symptoms.
ACE inhibitors & other medicines
ACE inhibitors are medicines that are commonly prescribed for blood pressure (and other conditions). They include medicines such as enalapril, captopril and lisinopril. One of the most common side-effects of this class of drug is a dry cough with throat irritation. A chronic cough usually starts when you start taking the medicine, and in this situation, most patients realise the cause. However, it can occur some time after you start taking it, in which case the connection between the two is sometimes not made. It is such a common side-effect of this class of drug, that a variation of the medication has been developed (angiotensin II receptor antagonists) with which a cough is a less common side-effect.
Many other medicines can also cause a chronic cough, although not so frequently as with ACE inhibitors.
Smoking causes chronic irritation of the airways and is a common cause of a chronic cough. Curiously, stopping smoking can also cause a cough in some people. This is because the cells that line the airways start working more effectively. These cells clear mucus and debris out of the airways, which can cause a cough. Fortunately, this usually settles with time, although it can take weeks or even months.
Less common causes include:
Vocal cord paralysis