All patients with chronic cough should be evaluated by their physician. This article is for informational purposes and covers only major causes of chronic cough. A listing of all the possible causes of chronic cough is beyond the scope of this article. Please consult with your physician.
In patients who are smokers, with either a normal or an abnormal chest X-ray, common causes include bronchitis and lung cancer.
Non-smokers with chronic cough are most likely to have one of three entities: post-nasal drip, asthma or laryngeal pharyngeal reflux (LPR).
Post-nasal drip is by far the most common cause of cough and could come from allergies, sinusitis, nasal polyps or non-allergic rhinitis. Skin testing is useful in evaluating for allergies.
Asthma causing cough (known as cough-variant asthma) is less common than the usual type of asthma, which causes wheezing. A computerized breathing test (spirometry) can often reveal evidence of asthma in these cases but asthma may be episodic and patients with cough variant asthma may have normal spirometry in the office. A special test such as methacholine challenge may be necessary in such cases.
Laryngeal pharyngeal reflux (LPR) is increasingly more recognized as a cause of chronic cough. It is however, the most difficult to diagnose without sophisticated test equipment. We have more on LPR below.
Besides these three entities, as mentioned, there are many other diseases that can cause chronic cough.
Drugs may cause a chronic cough. In particular, a group of drugs called ACE inhibitors used to treat high blood pressure and heart problems can cause a chronic cough.
10% of adults with prolonged cough (>14 days) may have a milder form of the childhood illness whooping cough or pertussis. Pertussis lasts for several weeks or longer and the cough is attributed to “bronchitis”. There are usually two weeks of common cold symptoms, followed by two weeks of severe coughing, followed by two weeks of a convalescent period when coughing occurs less often. Adolescents and adults may also develop complications of pertussis such as difficulty sleeping, urinary incontinence, pneumonia, and rib fracture.
The third most common cause of chronic cough is laryngeal-pharyngeal reflux (LPR). Unlike the related GER, patients with LPR don’t often have heartburn or regurgitation. The most common LPR symptoms are throat clearing, cough, a sensation of a lump or something stuck in the throat and hoarseness. With LPR, stomach contents (acid and digestive enzymes) back flow up the esophagus and into the larynx or voicebox. The Reflux Symptom Index (RSI) is a simple screening test for LPR. An RSI score above 13 is considered abnormal. Although you may have many symptoms in the table below which may suggest "LPR" you must consult your physician before assuming that you have "LPR."
--By Dr. John S. Kellogg