Gastroesophageal reflux disease (GERD) is a common condition where the stomach’s contents flow back up into the esophagus. This backward flow of acid can cause heartburn, but it can also lead to more subtle issues. GERD can cause a cough, which is a frequently overlooked cause of persistent respiratory distress. The cough linked to reflux is typically chronic, meaning it lasts for eight weeks or longer, and is often dry, with no mucus.
Establishing the Link Between Reflux and Chronic Cough
Chronic cough is a widespread problem, and reflux is recognized as one of the three most common causes, alongside asthma and post-nasal drip. For many individuals, the cough is the sole or primary symptom of their GERD, often occurring without heartburn. This cough frequently worsens when a person lies down, especially at night, or shortly after consuming a meal.
A specific form of reflux, known as Laryngopharyngeal Reflux (LPR), is often implicated in these cases. LPR is distinct from typical GERD because stomach contents travel high enough to reach the larynx (voice box) and pharynx (throat). Since the throat and vocal folds are more sensitive than the esophagus, this “silent reflux” can trigger a cough reflex even with minimal acid exposure. LPR is estimated to be responsible for chronic cough in up to 20% of patients.
The Physiological Mechanism of Airway Irritation
The connection between reflux and coughing is explained by two primary scientific theories: the direct irritation theory and the reflex theory. Both mechanisms involve the vagus nerve, which extends sensory branches to the esophagus, larynx, and lungs. These pathways explain why cough can occur even without classic heartburn symptoms.
Direct Irritation Theory
The Direct Irritation Theory, often associated with LPR, posits that liquid or vaporized stomach contents physically ascend into the upper airways. The sensitive tissues of the larynx and pharynx become irritated by acid, pepsin, or bile, triggering a protective cough reflex. Even tiny amounts of microaspiration, where stomach fluid enters the windpipe or lungs, can lead to chronic inflammation and a persistent cough.
Reflex Theory
The Reflex Theory, also called the esophago-tracheo-bronchial reflex, suggests that irritation in the lower esophagus is the trigger, even if the refluxate never reaches the throat. Fluid in the distal esophagus stimulates chemoreceptors and mechanoreceptors on the vagus nerve. This irritation sends a signal to the cough center in the brainstem, initiating a cough response as a protective measure. This means the cough is a neurogenic response to esophageal irritation, not necessarily a direct wash of acid over the vocal cords.
Both mechanisms may be at work in the same patient, contributing to a heightened cough reflex sensitivity. Non-acidic or weakly acidic reflux stimulates mechanical stretch receptors on nerve fibers in the esophagus. This stimulation, combined with possible neurogenic inflammation, contributes to the persistent nature of the reflux-induced cough.
Confirmatory Diagnostic Procedures
Diagnosing reflux-induced cough is often challenging, especially when typical symptoms like heartburn are absent. Clinicians frequently begin with an Empiric Trial of high-dose acid suppression medication, typically a Proton Pump Inhibitor (PPI), for several weeks to see if the cough improves significantly. A positive response to this trial strongly suggests a diagnosis of reflux-induced cough.
When the empiric trial fails or a definitive diagnosis is needed, specialized tests are employed to objectively measure reflux episodes. The gold standard diagnostic tool is Multichannel Intraluminal Impedance with pH Monitoring (MII-pH), a 24-hour ambulatory test. This test involves passing a thin catheter through the nose into the esophagus to detect all types of reflux—acidic, weakly acidic, and non-acidic—by measuring electrical conductivity (impedance).
MII-pH monitoring is superior because it detects non-acidic reflux, which is a common trigger for chronic cough. The test also assesses the Symptom Association Probability (SAP), a statistical measure of how likely a reflux event is related to a patient’s reported cough episodes. A diagnosis of reflux-induced cough requires a temporal relationship between the reflux episodes and the coughing events, and the cough resolving with anti-reflux treatment.
Management Strategies for Reflux-Induced Cough
Treatment for reflux-induced cough focuses on reducing the frequency and severity of reflux events to alleviate airway irritation. The first line of management involves targeted Lifestyle Modifications that reduce pressure on the stomach and prevent upward flow of contents. Elevating the head of the bed by six to eight inches, using blocks or a wedge, is recommended to allow gravity to keep stomach contents down.
Dietary adjustments are important, including avoiding trigger foods such as caffeine, alcohol, fatty or spicy meals, and chocolate, which relax the lower esophageal sphincter. Patients should eat smaller, more frequent meals and avoid lying down for at least two to three hours after eating. Maintaining a healthy weight and quitting smoking are also recommended, as both factors increase intra-abdominal pressure and weaken the esophageal sphincter.
Pharmacological Treatment
Pharmacological Treatment typically involves acid suppression medications, with Proton Pump Inhibitors (PPIs) being the most common first-line therapy. PPIs effectively reduce the amount of stomach acid produced, minimizing the irritating potential of reflux. H2 blockers, such as famotidine, can also be used, sometimes in combination with PPIs, to further suppress acid.
Treatment for reflux cough often requires a longer duration, sometimes several months, and occasionally higher doses than treatment for typical heartburn. This is due to the increased sensitivity of the upper airways. Alginate-based agents, such as Gaviscon, are also used as they create a physical barrier on top of the stomach contents, preventing reflux from reaching the upper esophagus.