Simple Surveys May Help Phenotype and Target Treatment for Chronic Cough

In recent years, chronic cough has been recognized as a unique condition, not solely a symptom of other diseases. A recent study published in Respiratory Medicine assessed the prevalence and distribution of chronic cough as well as the characteristics of different phenotypes in the Austrian population.

Chronic cough is defined as a consistent cough lasting 8 weeks or more, and the concept of cough sensitivity has been suggested as the condition’s underlying mechanism. Its prevalence has been estimated at 9.6% globally and 12.7% in Europe alone. The European Respiratory Society (ERS) guidelines suggest cough hypersensitivity syndrome as the overarching diagnosis, with phenotypes including:

• asthmatic cough/eosinophilic bronchitis
• gastroesophageal reflux disease (GERD) cough
• postnasal drip syndrome/upper airway cough syndrome (UACS)
• angiotensin-converting enzyme inhibitors (ACE inhibitor) cough
• chronic refractory cough (or unexplained/idiopathic chronic cough)
• chronic cough in other diseases
• chronic cough related to tobacco and nicotine

The study aimed to provide clarity on the prevalence and characteristics of chronic cough phenotypes in the general population based on a large cohort from the Lung, hEart, sociAl, boDy (LEAD) study (NCT01727518) in Austria.

Data from a total of 10,057 adults were pulled from the LEAD study, and 868 (9%) of those participants had chronic cough. More than 80% of participants had a chronic cough for more than 1 year, and 31.9% had a cough lasting more than 5 years. The median cough duration was 3 years.

Chronic cough prevalence increased with age across the cohort, and gender was not significantly associated with cough prevalence in the general cohort. In never smokers, though, it was more common in women, who made up 68.4% of never smokers with chronic cough.

Nearly 66% of those with chronic cough were overweight or obese (39.1% and 25%, respectively). Overall, 30.9% of the study population had arterial hypertension and 94.5% of those participants were treated with an ACE inhibitor. Of all the participants treated with ACE inhibitors, 13.6% had chronic cough.

Where cough phenotypes are concerned, 85% of the chronic cough cohort had associated conditions, and patients could belong to more than one group in this analysis. Of all chronic cough patients, 40.8% were current smokers; 32.6% took ACE inhibitors; 18.2% had GERD; 17.6% had asthmatic cough; 9.7% had UACS; and 28.3% had other diseases associated with chronic cough. A total of 12.7% of participants with chronic cough had an airflow limitation.

Unexplained chronic cough was present in 15.3% of the chronic cough cohort, and 45.1% of those participants had a past smoking history. In those with more than 30 pack-years of smoking history, 27% had chronic cough versus 10.6% who did not. Overall, asthma, GERD, COPD and UACS, older age, current (but not former) smoking, low socioeconomic status, obesity, and obstructive sleep apnea were all associated with chronic cough in this study population.

Study limitations included the lack of cough-specific questionnaires and potential overestimation of ACE inhibitor intake and unexplained phenotypes, since there was no ACE inhibitor or smoking withdrawal trial involved in the analysis. A lack of cough-specific therapeutic trial data was also a limitation, as such data would help confirm that participants’ chronic cough was refractory.

Still, the study provides evidence that most chronic cough cases likely fall within a phenotype and that treatment can be targeted to a particular patient’s case.

“The majority of individuals with chronic cough (85%) can be assigned to a specific phenotype by a simple questionnaire-based assessment and can therefore potentially receive specific treatment,” the authors concluded.

Reference

Abozid H, Baxter CA, Hartl S, et al. Distribution of chronic cough phenotypes in the general population: A cross-sectional analysis of the LEAD cohort in Austria. Respir Med. Published online December 29, 2021. doi:10.1016/j.rmed.2021.106726