Prevalence and risk factors for refractory and untreated chronic cough in the Canadian Longitudinal Study of Aging

Chronic cough, defined as a persistent cough lasting >8 weeks, affects 16% of Canadian adults in the community. Chronic cough can be classified as refractory chronic cough when cough persists despite treatment of any identifiable underlying condition. The prevalence of refractory chronic cough is unclear, as is the number of patients who remain untreated despite having a persistent cough.

This prospective cohort study included 26 606 adults of 45-85 years old from the Canadian Longitudinal Study of Aging (CLSA) with available chronic cough data at baseline and first follow-up at 3 years. Chronic cough was defined by self-reported daily cough for ≥12 months.

In this cohort, 4059 participants had a cough at baseline. Among them, 26.2% had refractory chronic cough on medications, 27.4% had chronic cough without medication (untreated chronic cough), 19.3% had resolution of chronic cough with medication, and 27.1% had resolution of chronic cough without medication. Overall, the prevalence of refractory chronic cough was 4.0% (1063 out of 26 606) among patients on medication and 4.2% among the untreated chronic cough group. Refractory chronic cough was more common in men, persistent smokers and those with asthma, COPD, migraine and inflammatory bowel disease or irritable bowel syndrome. Smoking cessation and discontinuation of angiotensin-converting enzyme inhibitors were associated with resolution of cough. Despite guideline-recommended therapies, neuromodulators were infrequently prescribed by physicians.

This population-based study was able to explore the outcomes of chronic cough over 3 years and identify risk factors with its development. Nearly one third of cases resolved without new medication, but likely by targeting treatable traits such as smoking and stopping angiotensin-converting enzyme inhibitor use.