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 a rare cause of chronic cough but most important, is lung cancer.
Non-smokers with chronic cough are most likely to have one of three entities: post-nasal drip, asthma or Gastro-esophageal reflux disease (GERD)
Post-nasal drip is by far the most common cause of cough. It is not really a cause, but a symptom and could be caused by allergic rhinitis (nasal allergies), sinus infection, 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.
Gastroesophageal reflux disease (GERD) In patients with chronic cough who also complain of typical and frequent GI complaints such as daily heartburn and regurgitation, especially when the findings of chest-imaging studies and/or clinical syndrome are consistent with an aspiration syndrome.
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.
Laryngeal-Pharyngeal Reflux (LPR) is not the same as gastroesophageal reflux disease (GERD)
Another cause of chronic cough is laryngeal-pharyngeal reflux (LPR. Unlike the related GERD, 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) backflow 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.
Reflux Symptom Index
Within the last MONTH, how did the following problems affect you?
0 = no problem, 5 = severe problem
| 1. Hoarseness or a problem with your voice | 0 1 2 3 4 5 |
| 2. Clearing your throat | 0 1 2 3 4 5 |
| 3. Excess throat mucus or post nasal drip | 0 1 2 3 4 5 |
| 4. Difficulty swallowing food, liquids, or pills | 0 1 2 3 4 5 |
| 5. Coughing after you ate or after flying down | 0 1 2 3 4 5 |
| 6. Breathing difficulties or choking episodes | 0 1 2 3 4 5 |
| 7. Troublesome or annoying cough | 0 1 2 3 4 5 |
| 8. Sensations of something sticking in your throat or a lump in your throat | 0 1 2 3 4 5 |
| 9. Heartburn, chest pain, indigestion, or stomach acid coming up | 0 1 2 3 4 5 |
Total |
In a recent article in the October 20, 2016 issue of the New England Journal of Medicine, Smith and Woodcock state:
“Whereas the “diagnostic triad” of asthma, gastroesophageal reflux, and postnasal drip have been considered to be the major causes of chronic cough, and high success rates have been claimed for treatments targeting these conditions, several observations raise questions about this concept. First, the large majority of patients who present with these common conditions do not report coughing excessively. Second, despite careful guideline-driven testing and treatments, many patients with chronic cough either have no response to the treatment of the underlying conditions or have no identifiable cause of the cough, and the cough persists. An alternative theory is that an abnormality of the neuronal pathways controlling cough is likely to be the primary disorder in these patients, with identified causes (including asthma, reflux, and postnasal drip) acting as triggers only in the context of neuronal cough hyperresponsiveness.”
In my experience, allergies play a large role in some patients with chronic cough and I have a number of patients who have responded well to allergy shots after antibiotics, anti asthma medications and anti-GERD medications have not helped.