Ask Dr James: What is the root cause of my five year long cough?

Dear Dr James,

For almost five years now I have endured a persistent hacking cough several times a day, but at its worst comes every few minutes. I have been tested for asthma and had numerous tests, scans and X-rays but there seems to be no clear explanation other than the suggestion it may be “stress related”.

Dear reader,

Coughing is indispensable. Without this highly efficient method of ensuring the airways remain open and free of obstruction, the flow of oxygen into the lungs would be seriously compromised. The cough reflex (as it is known) is initiated by stimulation of sensory nerves (cough receptors) in the larynx and airways. This generates a stream of nerve impulses to the brain activating the synchronous contraction of the muscles of the chest wall, culminating in the forcible expulsion of air from the lungs. Disturbed functioning of any aspect of this reflex can give rise, as in this query, to tiring, tiresome and purposeless bouts of coughing. When all obvious causes have been excluded, several ‘hidden’ explanations need to be considered.

Post-viral cough

Many trace the onset of their persistent cough to a preceding, usually viral, infection of the lungs… There may be several reasons for this but in some it is due to an inflammatory process, triggered by the virus, that prevents the healing of the damaged lining of the airways. Here, a week-long course of high-dose steroids may be curative by suppressing the inflammation.

Asthma

There is little difficulty in diagnosing the characteristic wheeze and breathlessness of asthma. But sometimes, especially in children, its sole manifestation may be a persistent nocturnal cough – readily preventable by a bedtime dose of the bronchodilator Ventolin.

Acid reflux

Reflux of the acid secretions of the stomach may tip over into the airways to irritate the lungs. “Mrs V was a 66-year-old woman who had suffered a daily non-productive cough for 20 years” reports Dr Paul Glasziou in the BMJ. It transpired on further questioning that she was also intermittently troubled by heartburn at night. He advised her to raise the head of her bed and take an acid suppressant medication before retiring. “The cough settled within a few days and six months later has not returned.”

Drug side effects 

Cough is not a common side effect of medications, the most frequent offender being the blood pressure lowering angiotensin-converting-enzyme (ACE) inhibitors, such as Ramipril. Interestingly, the British Nobel Prize Winner Sir John Vane was amongst the first to describe this phenomenon from personal experience. “Not surprisingly I have always been a strong advocate of ACE inhibitors and have taken them myself” he recalled. Until he began to cough so violently “it sometimes led to retching”, compelling him to switch to a different class of drug.

Cough hypersensitivity syndrome

It is obviously important to identify these ‘hidden’ – and for the most part gratifyingly remediable – causes of cough. For most, it remained unexplained until a major breakthrough just a few years ago: the realisation that many of those afflicted had cough hypersensitivity syndrome. Here, as the name suggests, the sensory cough receptors are hypersensitive to stimuli that would not normally induce the cough reflex, such as the normal flow of air in and out of the lungs when for example taking a deep breath, laughing or talking excessively on the phone. In a variant, this hypersensitivity may be perceived as an intermittent tickling irritating sensation in the throat. The significance of this insight is in allowing for the quite different therapeutic approach of medicines, such as amitriptyline, that dampen down the nerve impulses generated by those hypersensitive receptors.

Email queries and comments in confidence to Drjames@telegraph.co.uk