Gastroesophageal reflux disease (GERD) is a condition where stomach acid persistently flows back up into the esophagus, the tube connecting the mouth and stomach. This backwash irritates the esophageal lining and commonly causes heartburn. However, it can also manifest in ways seemingly unrelated to the digestive system. A chronic cough can be a direct sign of acid reflux, especially when other common causes have been excluded.
The Reflux-Cough Connection
Acid reflux is a common, yet often unrecognized, cause of a long-lasting cough. A chronic cough is defined as one that persists for eight weeks or longer. Research indicates that GERD is associated with 25% to 40% of chronic cough cases.
The cough caused by reflux can be the only symptom present, without typical heartburn or regurgitation. This makes diagnosis difficult, as patients may not suspect a stomach issue is the root cause. A persistent cough that worsens when lying down or shortly after eating may suggest a connection with acid reflux.
Mechanisms That Cause the Cough
Reflux triggers a cough through two main biological pathways involving irritation and protective reflexes.
The first mechanism is the esophago-bronchial reflex, a nerve-based reaction. Acidic stomach contents irritate the lower esophagus, which shares nerve pathways with the airways via the vagus nerve. This irritation signals the brain to activate a protective cough reflex, even if the acid never reaches the throat or lungs.
The second mechanism involves microaspiration, where tiny droplets of stomach contents travel high up into the throat and are inhaled into the airway. When these droplets reach the sensitive tissues of the larynx, trachea, or lungs, they cause direct irritation and inflammation. This chemical irritation triggers a persistent cough as the body attempts to clear the foreign material. Stomach contents, which contain acid and components like pepsin, can be damaging even in small amounts once they enter the respiratory tract.
Silent Reflux: Coughing Without Heartburn
Many people with a reflux-related cough do not have the classic burning sensation of heartburn. This condition is often referred to as Laryngopharyngeal Reflux (LPR) or “silent reflux.” LPR occurs when stomach contents travel up to the larynx (voice box) and pharynx (throat). Unlike typical GERD, LPR does not linger in the esophagus long enough to cause the burning pain associated with heartburn, which is why it often goes unnoticed.
The lining of the throat and voice box is far more sensitive to acid damage than the resilient lining of the esophagus. Therefore, even a small amount of reflux can cause irritation in the upper airway. The symptoms of silent reflux are typically respiratory and laryngeal. These include a chronic cough, frequent throat clearing, hoarseness, or the sensation of a lump in the throat. Because these symptoms mimic other conditions like allergies or post-nasal drip, LPR is frequently misdiagnosed.
Next Steps for Diagnosis
If a persistent cough lasts longer than eight weeks, especially without a clear cause like infection or asthma, it warrants medical evaluation. The first step involves a detailed medical history to rule out other common causes, such as certain medications or chronic respiratory infections.
A doctor may initially recommend an empirical treatment trial using a strong acid-suppressing medication, such as a proton pump inhibitor (PPI), for a defined period. If the cough improves significantly during this trial, it provides strong evidence that reflux is the underlying cause.
For cases where the diagnosis remains unclear or the treatment trial is unsuccessful, more specialized tests may be necessary. These diagnostic methods include 24-hour pH monitoring or multichannel intraluminal impedance with pH monitoring (MII-pH). These tests measure acid and non-acid reflux episodes and their temporal association with coughing events. An upper endoscopy, which uses a flexible tube with a camera, may also be performed to look for damage caused by reflux.