Acid reflux and chronic cough
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Acid Reflux and Chronic Cough: Association and Mechanisms
Prevalence and Types of Reflux in Chronic Cough
Gastroesophageal reflux (GERD) is a well-recognized cause of chronic cough, even in patients who do not have typical reflux symptoms like heartburn. Studies show that both acid and non-acid (weakly acidic or weakly alkaline) reflux can trigger cough episodes in adults and children, with a significant number of cough events occurring shortly after reflux episodes of varying acidity 210. In many cases, chronic cough is associated with otherwise asymptomatic reflux, highlighting the importance of considering GERD in patients with unexplained cough 4510.
Mechanisms Linking Reflux to Cough
Research indicates that the physical characteristics of reflux episodes—such as the volume of refluxate, how far it travels up the esophagus, and how long it remains there—are more important in triggering cough than the acidity alone. Longer esophageal exposure and larger reflux volumes are more likely to induce cough, while the actual pH (acidity) of the refluxate is less relevant . This may explain why many patients with chronic cough do not respond well to acid-suppressive therapy 17.
A proposed mechanism involves a local neuronal reflex between the esophagus and the airway, where reflux stimulates nerves that trigger coughing. In turn, coughing can increase reflux by raising pressure in the abdomen or relaxing the lower esophageal sphincter, creating a self-perpetuating cycle .
Diagnostic Approaches
Ambulatory 24-hour pH-impedance monitoring is the most sensitive method for detecting both acid and non-acid reflux and for establishing a temporal association between reflux and cough 210. However, even with this technology, only a subset of patients show a clear link between reflux events and cough, suggesting that other factors may also contribute 27.
Response to Acid Suppression Therapy
The effectiveness of acid-suppressive therapy (such as proton pump inhibitors) for chronic cough is mixed. Some studies report modest benefits, especially in patients with proven pathological acid exposure, while others find little to no improvement 5678. The benefit is more likely in patients with objective evidence of acid reflux, and less likely in those with non-acid reflux or in whom cough is not temporally linked to reflux events . In children, both acid and non-acid reflux can be associated with chronic cough, and the absence of increased acid exposure time in cough-related reflux suggests that acid suppression may not always be effective .
Impaired Esophageal Clearance
Patients with chronic cough often have impaired clearance of refluxed material from the esophagus, leading to longer exposure times and increased likelihood of cough 19. This impaired clearance may be a key factor in the development and persistence of cough in these patients.
Conclusion
Chronic cough is frequently associated with both acid and non-acid gastroesophageal reflux, often in the absence of typical reflux symptoms. The physical properties and duration of reflux episodes, rather than acidity alone, are important in triggering cough. Acid-suppressive therapy may help some patients, particularly those with proven acid reflux, but is less effective in others, especially when non-acid reflux is involved. Comprehensive diagnostic evaluation, including pH-impedance monitoring, is essential to identify patients who may benefit from targeted therapy.
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