Chronic Cough: Hidden Causes & Cures
Author: Thomas Beller
Chronic cough can be defined as a cough lingering for eight weeks or longer and is one of the more frustrating problems a patient can experience. In fact, more than half of patients suffering from chronic cough will become clinically depressed. The purpose of this article is to identify some of the common but elusive causes of chronic cough and discuss how to alleviate them.
In contrast to an acute cough, which is often caused by a respiratory infection, chronic cough is rarely caused by infection. The most common causes of chronic cough include gastroesophageal reflux disease, post-nasal drip, asthma and chronic obstructive pulmonary disease (COPD—formerly chronic bronchitis and emphysema). Patients who have significant cough in relation to asthma or COPD will usually have objective features, such as wheezing, that reveal the diagnosis. Here, we will focus on the more subtle causes of chronic cough: acid reflux disease and chronic sinusitis.
Conditions of the nose and sinuses are often thought to cause cough because of significant post-nasal drip. One condition linked to chronic cough is chronic sinusitis. In most cases, chronic sinusitis is not an infection; rather, it is a chronic inflammatory disease. It often involves the same type of inflammation that we see in asthma, but is in a different part of the airway (the sinuses). It sometimes triggers asthma. Not all patients with chronic sinusitis will cough, but pediatric patients and elderly patients often have cough as a feature of chronic sinusitis. Young adults can also have cough as a feature of chronic sinusitis, sometimes presenting as recurring bronchitis and/or pneumonia. Even though pneumonia and bronchitis are infections, they often begin with airway inflammation that starts in the sinuses and “spreads” to the lower airways. Bacteria can gain an advantage in these inflamed areas and trigger an infection. An imaging study of the sinuses, preferably a CT scan, should be considered in patients who have chronic productive cough or recurring bronchitis or pneumonia. This condition can be easily seen on a CT scan as thickening of the mucosal lining in the sinuses.
In children with chronic cough related to chronic sinusitis a topical nasal steroid spray will usually alleviate the cough or at least allow for significant improvement. It doesn’t eliminate the problem, but controls it as long as the medication is used regularly. Sometimes the cough gets worse before it improves, possibly because the sinuses are releasing their mucous as the drainage areas first start to open up. Usually, within 7-10 days, the cough will dissipate significantly. Over time, the condition usually improves as the child grows. However, some patients require treatment with a nasal steroid spray for a year or longer. Antihistamines are typically ineffective or minimally effective at controlling symptoms of chronic sinusitis. In severe cases, adenoidectomy can be helpful, sometimes dramatically so.
In adults, chronic sinusitis is most responsive to oral steroids, such as prednisone. Many patients will require a two- to three-week course of prednisone to gain control of the sinus inflammation. Thereafter, topical nasal steroids and nasal lavage (flushing the nose with a saltwater solution) can help keep the sinus inflammation and cough under control.
The exact cause of chronic sinusitis is unknown. Poor drainage of the sinuses, due to obstruction of the drainage pathways to the nose may be a contributor. Sometimes anatomical factors are thought to contribute. Allergies can also contribute in roughly 50 percent of patients. In patients who have chronic sinusitis related to allergies, a course of desensitization therapy (allergy shots) can be very helpful, especially if the disease is caught early. In patients who have severe sinus problems for many years, controlling the allergies might not make as much difference.
The other common hidden cause of chronic cough is silent acid reflux. Most cases of chronic cough that have gone undiagnosed for years are related to silent acid reflux. These patients commonly do not have indigestion. Cough can be the only feature of acid reflux, sometimes accompanied by post-nasal drip. The nature of the cough can be strongly suggestive of the diagnosis. Patients with reflux-induced cough usually have a non-productive cough that is somewhat spasmodic in nature. This cough often stops patients in mid-sentence with an uncontrolled spasm of the diaphragm that often repeats itself over several breaths. Although the cough is typically dry, patients will often describe that they have mucous in their chest, but they feel like they just can’t get it up. They also commonly complain of an irritating “tickle” in the upper airway or throat. The cough may be most prominent after a large meal, while lying down flat, or while laughing or talking.
The cause of reflux-induced cough is poorly understood. A simple theory is that acid makes its way up the esophagus and into the airway. Most researchers dismiss this simple theory and believe there are also complex nervous reflexes involved. Both doctors and patients can easily misdiagnose this cough. It is often unaccompanied by indigestion, and there are sometimes minimal findings on tests commonly used to secure the diagnosis. The best way to diagnose reflux-induced cough is to try treating it with the appropriate medical regimen. It does not usually respond as well to acid suppressing medications as indigestion does. The strongest acid reducers, called proton pump inhibitors, often have to be used at maximal prescription strength doses to have an effect.
GABA-B receptor agonists are another class of medications that can be even more helpful than proton pump inhibitors for reflux induced cough. There are GABA-B receptors on the sphincter above the stomach. When these receptors are activated, they inhibit excessive relaxation of this sphincter, preventing reflux. These medications (e.g. Gabapentin, Baclofen) are highly effective but can cause sedation when initiated. Drug companies are working quickly to develop newer drugs that do not affect the brain and can avoid sedation as a side effect (see Lesogaberan, TM AstraZeneca).
Patients with chronic cough should seek medical attention. Your doctor will first want to rule out worrisome conditions and may uncover an obvious diagnosis. If not, these elusive conditions should be considered.