9 October 2019

Chronic cough a disease, not a symptom

Clinical Respiratory

Chronic cough is a disease entity in its own right, not a symptom, according to newly released guidelines from the European Respiratory Society.

The head of the guidelines taskforce Professor Alyn Hugh Morice, from the Respiratory Research Group at Hull University, told the ERS Congress in Madrid that vagal hypersensitivity was what underlay most chronic cough in adults.

Because most patients had a common clinical presentation – extreme sensitivity to inhaled irritants such as perfumes and cold air – and because two-thirds were middle-aged women, cough hypersensitivity syndrome was now its own diagnosis, with different phenotypes depending on the type and location of the inflammation.

“We now have an understanding of cough and chronic refractory cough,” Professor Morice said. “It is a disease characterised by hypersensitivity of the vagus nerve. It’s not a hunt for the cause of the cough: cough hypersensitivity is the overarching diagnosis, and there are different phenotypes within that.”

These types are asthmatic cough or eosinophilic bronchitis; reflux cough (which shouldn’t be treated with PPIs unless it came with peptic symptoms); postnasal drip syndrome (this is an American invention, in my view) or upper airways cough syndrome; iatrogenic cough in those taking ACE inhibitors; idiopathic or chronic refractory that defied conventional treatment; and chronic cough from other diseases such as insterstitial lung disease.

Professor Morice urged the audience not to dismiss chronic cough as trivial, as it was a profound influencer on quality of life – worse than COPD – causing urinary incontinence, sleep disruption and social embarrassment.

“It’s a major, major source of morbidity out there in the population, and we have an incidence rate that is bigger than asthma,” he said.

Children were different from adults, he said – “I usually refer to them as a small animal model” – and their chronic cough should be further investigated for underlying causes.

One of the most controversial recommendations in the guidelines is for patients who stop smoking. Because nicotine suppresses cough, quitters may experience higher cough sensitivity and may be helped by e-cigarettes, if the coughing was likely to drive them back to tobacco.

Initial assessment should always include a chest X-ray and pulmonary function test, with FeNO and blood eosinophil counts less crucial.

Initial management should be stopping risk factors and initiating corticosteroids or antileukotrienes. If there was improvement at follow-up, continue for a few months before attempting withdrawal.

If there was no improvement, further options to consider were low-dose morphine, which Professor Morice said could be “absolutely miraculous” in chronic cough; a promotility agent such as metoclopramide, though these had a poor evidence base; gabapentin or pregabalin, although questionable efficacy and side effects made them a last resort; and cough control therapy from an experienced practitioner.

The simplest way to measure progress was to ask a patient to score their cough out of 10 at baseline and compare the score after a period of treatment.

ERJ, September 2019