DEAR DOCTOR K:
I’ve been coughing for weeks. Why won’t this cough go away?
Every human being coughs, beginning from the first moments after birth. In fact, we probably cough when we’re still in the uterus.
Why do we cough? The answer probably is that coughing protects our lungs. Secretions from our nose and sinuses, or fluids in our mouth, can accidentally drop down into our lungs. Coughing is the lung’s way of expelling what has dropped into it — expelling it first from our lungs, and ultimately out through our throat and mouth.
A cough is triggered when nerves in the larynx (voice box) or respiratory tract are stimulated. These nerves can be irritated by infections, allergies, cold air, tumors, smoke, dust particles, nasal mucus or stomach acid.
Anatomy of a cough
The cough starts with a gasp that sucks air down into the lungs. Next, the epiglottis snaps shut over the trachea, or windpipe. Then the muscles of the diaphragm, abdomen, and chest contract forcefully. Pressure builds up until the epiglottis opens, releasing a rush of air that makes the characteristic sound of a cough.
Smoking is the leading cause of a chronic cough, but many nonsmokers develop chronic coughs as well. The lion’s share of these are caused by one or more of the following:
Postnasal drip. Viruses, allergies, sinusitis, dust particles and airborne chemicals can irritate the nasal membranes. The membranes respond by producing extra mucus. When this mucus drips down the throat, it triggers a cough.
Asthma. Wheezing and breathlessness are the usual symptoms of asthma. But some asthma patients just cough. That’s particularly true when they go outside in winter. For people with asthma, and some others, cold and dry air can irritate the breathing tubes. This causes the tubes to go into spasm, which leads to a cough.
Gastroesophageal reflux disease (GERD). Heartburn is the usual symptom of GERD. But GERD can cause coughing without heartburn. About one-third of patients with GERD complain of cough, recurrent laryngitis or unexplained sore throats. The stomach acid that gets regurgitated up into the throat irritates the nerve endings in the larynx and throat, and this triggers a cough.
Chronic bronchitis is a persistent infection of the bronchial tubes, which can lead to a chronic cough.
Therapy with angiotensin-converting–enzyme (ACE) inhibitors. ACE inhibitors are frequently used to treat high blood pressure. Unfortunately, cough is one of the side effects of these medications, occurring in up to 20 percent of patients.
Heart failure and lung cancer. It’s uncommon, but sometimes a chronic cough is the first sign of either heart failure or lung cancer. Fortunately, the other less serious medical conditions I’ve mentioned above are much more common causes of cough.
Coughing interrupts sleep, producing fatigue and impairing concentration. It also can cause urinary incontinence, and even fractured ribs.
A chronic cough is always worth discussing with your doctor. If it is accompanied by sputum production, bloody sputum, fever, weight loss, night sweats, breathlessness, undue fatigue or chest pain, consult your doctor without delay.