Experts say this common but under-recognised symptom is an important red flag for poor outcomes.
Patients with asthma or COPD who frequently have a “phlegmy” cough are more likely to have exacerbations and be hospitalised, according to new research.
“Frequent productive cough was present across all … severity levels, was associated with significant disease burden and was an important indicator of the risk of adverse clinical outcomes,” respiratory physician Professor Helen Reddel and colleagues wrote in Respiratory Medicine.
The Sydney asthma expert told ARR that a persistent wet cough was previously often only thought of in smoking-related lung disease, such as chronic bronchitis, but this study found it was also common in patients with asthma.
“Clinical guidelines about how to manage cough are mainly about dry cough, and research about cough is mainly about dry coughs,” said Professor Reddel, research leader at the Woolcock Institute of Medical Research.
However, the study found that only around one in 12 people with asthma or COPD reported having a persistent dry cough, while the wet cough was far more common.
The researchers examined the prevalence and severity of coughing with sputum production in more than 7100 patients with asthma, COPD or both, using self-reported data from 18 different countries.
They found that nearly a third of all participants reported having a frequent productive cough, which was defined as cough with sputum most or several days each week for the previous three months.
One in four asthma patients and more than one in three patients who had COPD or COPD with asthma reported this symptom.
Moreover, participants with a frequent productive cough were more likely to report significantly poorer health and had almost twice the odds of experiencing one or more exacerbations within the following year, including those requiring hospitalisation.
Patients with productive cough were more likely to be diagnosed with chronic bronchitis and bronchiectasis, to be receiving triple therapy and to report worsening symptoms in the three months prior to the study onset.
Patients with the frequent wet cough were more likely to have been exposed to pollutants at work or home, and have reduced post-bronchodilator FEV1.
For doctors treating asthma and COPD patients who present with persistent productive cough, Professor Reddel said the important thing to do was to establish how long patients had the cough, as this helped identify whether it was caused by something treatable.
She also emphasised the need for additional monitoring of these patients, given the increased likelihood of more frequent and severe flareups of their asthma or COPD.
“From a clinical perspective, if I saw a patient who has been coughing for up to three months, what I would do is find out what was happening when it started.
“If it just started, say, three or four months ago after a chest infection, then I would first get them to do some specific physiotherapist-designed exercises called Active Cycle of Breathing to help clear the mucus. I would make sure that they’re clearing the mucus effectively, and sometimes this resolves the problem.
“If it doesn’t go away, then I would likely order either a chest X-ray or CT scan, get a sample of the sputum to see if it’s growing any particular bugs, and measure the patient’s lung function.”
And if the patient had asthma or COPD, that should be treated effectively as well, she said.
Professor Reddel said a scan may identify some causes, such as bronchiectasis. Patients with that condition required regular physiotherapy that they could do at home, and possibly antibiotics.
This study, which was funded by AstraZeneca, is one of the first to explore this recurrent coughing with sputum in asthma patients as well as those with COPD, and to establish it as a descriptor separate to chronic bronchitis as it has historically been defined.
In addition, Professor Reddel said the pandemic had only increased the need for the causes of this cough to be identified, given the social stigma attached to coughing in public.
“Although it’s distressing for patients at any time, it’s not a pleasant symptom to have, particularly now because with covid it’s quite socially disabling to have a persistent cough, and I think that will probably continue,” she said.
“Patients with asthma or COPD and frequent productive cough, but not those with asthma+COPD, had higher blood neutrophil and eosinophil counts than those without frequent productive cough,” the researchers reported.
Those who had asthma or both respiratory conditions were more likely to have gastroesophageal reflux disease (GERD) and those with asthma only or COPD only were more likely to have coronary heart disease or heart failure, the researchers found.
“Allergic rhinosinusitis was associated with frequent productive cough in patients with asthma+COPD or COPD, whereas non-allergic rhinosinusitis was associated with frequent productive cough in patients with asthma.”
