Cough it up


  • Health
  • Sunday, 20 Jul 2008

The common causes of a chronic cough.

ONE month ago, my husband had a cold and sore throat. Since then, he has been coughing persistently and it hasn’t gone away. Why has his cold not recovered? Isn’t one month too long to be still having a cough?

It’s possible your husband has developed complications from the simple cough and cold, such as a post-nasal drip.

Nevertheless, a persistent or chronic cough is considered one only if its duration is more than eight weeks. Your husband has not tripped into that category just yet.

Smoking is notthe only cause ofa chronic cough.- AFP photo

Coughs caused by respiratory tract infections are usually self-limiting. Coughs are considered acute when they are less than three weeks. From three to eight weeks, they are considered subacute.

Subacute coughs, like your husband’s, is usually due to the irritation of his cough receptors after an infection. After an infection, your airways top lining (epithelium) might be destroyed, leading to increased sensitivity to any stimuli (called hyper-responsiveness). This subsequently goes away as your epithelium and mucosa heals.

Apparently, a cough is the single most common symptom people seek a doctor’s treatment for and is accountable for millions of dollars spent, not to mention the huge amount of medical certificates given and days laid off from work. The prevalence of cough in any given population depends on how much that population smokes.

Why do people cough in the first place?

You need to cough as part of your natural body’s physiological defence because you need to clear all the debris and micro-organisms that can be trapped in your airways and their secretions. The very fact that you breathe causes air and all its contaminants to enter your airways.

Coughing is usually not part of your consciousness (unless you purposely do it). In your airways such as your trachea (the main tube leading from your nose and mouth to your lungs), bronchi and their subsequent branches, there are cough receptors in the upper lining.

There are two types of cough receptors: Irritant receptors – these are triggered by toxic fumes and liquids, such as smelling ammonia; Mechanical receptors – these are triggered by physical things such as touch, stretch or displacement. Examples are if you breathe air too suddenly and deeply or if water wrongly enters your airways.

Bacteria and viruses invading your airways can lead to too much secretion, which can also stretch your cough receptors, causing you to cough.

What then causes some people to cough for more than two months? What is the most common cause?

There are many causes for a chronic cough.

Postnasal drainage is now thought to be the most common cause, which might account for as many as 87% of all cases, either singly or associated with other diseases.

The cough receptors in your upper airways keep getting stimulated as a result of allergic rhinitis, rhinitis after an upper respiratory tract infection or other forms of rhinitis. (Rhinitis = inflammation of your nasal passages)

Usually, a lot of other symptoms are associated with this postnasal drainage cough, such as persistent nasal discharge, nasal congestion and a frequently blocked nose, a ticklish sensation at the back of your throat and a persistent need to constantly clear your throat.

Oh? I always thought chronic cough was due to cigarette smoking.

That’s another very common cause – smoker’s cough. But smokers tend to get another more sinister disease that will cause chronic cough – this is called chronic bronchitis.

Chronic bronchitis is characterised by a cough producing phlegm for most days for at least three months in a year in two consecutive years. The patients are usually smokers, though in a small percentage, inflammatory bowel disease may also trigger it.

Other causes of a chronic cough are asthma, which is the second most common cause of chronic cough in adults, gastro-esophageal reflux (GERD), certain medications like ACE inhibitors used for hypertension, and bronchiectasis.

You mean gastro-esophageal reflux causes cough?

Gastro-esophageal reflux disease or GERD actually accounts for up to 40% of causes for chronic cough. What happens is that the acid from your stomach gets refluxed back to your oesophagus (the tube leading from your mouth to your stomach). In the lower part of your oesophagus, there are branches of the vagus nerve, the nerve which supplies most of your internal bodily organs and is responsible for breathing, swallowing and digestion.

When the vagus nerve branches in your lower oesophagus is stimulated by this stomach acid, which is not supposed to be there, what occurs is a complicated reflex loop which results in cough as the vagus nerve also supplies your respiratory tract.

Dr YLM graduated as a medical doctor, and has been writing for many years on various subjects such as medicine, health advice, computers and entertainment. The information contained in this column is for general educational purposes only. Neither The Star nor the author gives any warranty on accuracy, completeness, functionality, usefulness or other assurances as to such information. The Star and the author disclaim all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.


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