There are many people who seek medical attention due to a persistent cough. In fact, coughing is one of our biological defense mechanisms and it should not be needlessly suppressed. If you experience initial symptom which accompanies coughing, it is rather important to dilate the bronchial tubes and make coughing easier to expel any irritant.
On the other hand, a persistent cough puts stress on your body and becomes a nuisance. In this article, neurologist Dr. Yoshiya Hasegawa provides helpful information about the causes and precautions of a persistent cough.
Contents
1. The facts about cough which you should know
There are various types and conditions of coughs.
1-1.Period of a cough
Cough is classified into three categories based on its duration: An acute cough is a cough which disappears within three weeks; a subacute cough exists for three to eight weeks; and a chronic cough lasts for more than eight weeks. Clinical experience suggests that majority of an acute cough is commonly caused by respiratory tract infections. However, the longer the duration of the cough becomes, the lesser the possibility of respiratory tract infection being the trigger. In fact, it is believed that chronic cough does not stem from infections; many of them are triggered by other causes than infections.
1-2.Physical damage by coughing
Typically in one cough, you will burn as little as 2 kcal. If you cough ten times, you will burn about 20 kcal which over a long duration, might lead to significant damage in your body. To illustrate, this is equivalent to calories burned by walking for ten minutes.
1-3. Types of cough medicine
– Central antitussive: This medicine (codeine phosphate or astomin etc.) suppresses cough by interfering signals from the brain that trigger a cough reflex. Codeine phosphate is an inexpensive and effective narcotic antitussive which is available at stores and commonly used as a home drug because it is exempt from restriction when used as cough suppressants containing low doses of it.
– Peripheral antitussive: It involves bronchodilator (Theodur or Spiropent etc.) which suppresses cough by dilating bronchial tubes to increase airflow. This bronchodilator and expectorant are called peripheral antitussive drugs.
– Steroid: Steroid drug relieves symptoms caused by bronchial asthma or cough variant asthma.
– Definitive treatment: Taking cough suppressants is only a symptomatic relief. It is important to administer appropriate treatment to completely cure the disease.
2. Wet cough and dry cough
There are various types of coughs and each has different causes and conditions. Some should be suppressed immediately while others should not.
2-1. “Wet cough” has underlying causes
A wet cough is a cough that produces mucus or phlegm and it should not be suppressed because it is one of the defensive reflexes that help bring up phlegm or sputum. One of the treatments is decreasing excess mucus. Sinobronchial syndrome, post-nasal drip, chronic bronchitis, and lung cancer are thought to be the most likely causes of this type of cough.
2-2. “Dry cough” itself is a disease
A dry cough is uncomfortable and the cough itself is a disease which should be treated. Peripheral antitussive is a commonly used medication. Atopic cough, cough variant asthma, Angiotensin-converting enzyme (ACE) inhibitor-induced cough, gastroesophageal reflux disease, allergy-induced throat irritation, interstitial pneumonia, and tuberculosis (TB) are thought to be the most likely causes of this type of cough.
3.Causes and treatments of acute cough
Cough is typically caused by a cold
An acute cough which lasts for less than three weeks from its onset is one of the typical cold symptoms, and 90% of cold are caused by viruses. Our body tries to protect against viruses that enter airways or tries to get rid of excess phlegm by coughing. Most acute coughs disappear by themselves.
Dry cough where no phlegm is produced can be suppressed by peripheral antitussive. However, wet cough, a cough which brings up phlegm, should not be suppressed; it should be treated by dilating the airways or reducing the secretion so that irritants inside the airways can be pushed out of the body.
4. Postinfectious cough
People who visit an outpatient care often complain of a “cough which lingers even after other cold symptoms have disappeared” or “cough that won’t go away.” In this case, “postinfectious cough” is suspected. Postinfectious cough is defined as a persistent or chronic cough following a respiratory tract infection, which usually does not show any abnormal finding such as pneumonia and clears up on its own. This is to say, “a lingering cough which is caused by a cold and resolves by itself without specific abnormal findings found by medical examination.”
Postinfectious cough is diagnosed by how the condition of illness progresses. Medical examination is hardly administered at the first visit, however a chest X-ray, blood test, or pathogen test to check whether non-viral pathogens such as mycoplasma pneumoniae or bordetella pertussis are present, is administered in order to avoid underdiagnosing if the patient presents with the cough for more than three weeks.
It might be caused by mycoplasma pneumonia if the patient has a persistent cough for a long period of time after experiencing cold symptoms (fever, chillness, headache, runny nose, etc.).
5. Chronic cough
The most likely causes of chronic cough are sinobronchial syndrome, cough variant asthma and atopic cough. Patients diagnosed with gastroesophageal reflux disease are also increasing.
5-1.Sinobronchial syndrome
Sinus infection such as sinusitis leads to cough. Secretion or pus developed in the paranasal cavity makes mucus stickier. This sticky mucus slides down the back of the throat and causes cough in the morning or at night. This is because our body tries to get rid of mucus which is built up in the throat while sleeping. If the patient experiences cough while sleeping and sticky mucus coming out of their throat, they should visit an ENT specialist to be examined.
5-2.Cough variant asthma
(left) normal airway (right) asthmatic airway with thickened wall
People with cough variant asthma only have cough as a main symptom. The airways which become narrower increase sensitivity to various stimulation, and this leads to inflammation and cough attack as with common symptoms of asthma. Coughing may be triggered when patients are exposed to a sudden change in temperature, cigarette smoke, dust, house dust mite or when they exercise, drink alcohol, or feel stressed out. It does not cause other asthma symptoms such as wheezing.
Patients with a cold tend to experience cough variant asthma, and bronchodilator medication is often prescribed when they experience cough for longer than a couple of weeks. If the bronchodilator medication successfully suppresses cough, then they end up being diagnosed with cough variant asthma. It it one of the medical strategies where diagnosis is confirmed by efficacy of medication treatment.
5-3. Atopic cough
People with atopic cough only have cough as a main symptom as with cough variant asthma. When bronchodilator medication is administered to a patient suspected of having cough variant asthma and it does not fully work, then atopic cough should be considered as a second option. The patient may be experiencing atopic disorders other than asthma. Antiallergic agent (histamine H1 antagonists) such as Alesion or Allegra, or a steroid inhaler is used for the treatment.
5-4. Gastroesophageal reflux disease
Cough is not caused only by respiratory diseases; it is also caused by acid reflux. Generally, stomach acids produced in your stomach to aid digestion rarely move up into your mouth or esophagus. However, some people may experience acid backflow from the stomach, and it irritates their throat and causes cough.
Common symptoms of gastroesophageal reflux disease are heartburn, cough after overeating, and cough when lying down. However, it is very difficult to diagnose gastroesophageal reflux disease when cough is the only symptom present. It can be confirmed by finding esophagitis using an upper endoscopy, but some patients are still unable to get a diagnosis. In this case, medication is administered to reduce production of stomach acids. The diagnosis of gastroesophageal reflux disease is confirmed when this medication successfully relieves the cough.
6. Cough indicates life-threatening conditions
Some coughs may be a sign of life-threatening disease which cannot be overlooked.
6-1. Lung cancer
Lung cancer is one of the life-threatening illnesses: It is the leading killer cancer in males in Japan, and the number of female patients is also increasing. Possibility of lung cancer as a cause of chronic cough has to be eliminated early. If you are a smoker, have any family member who smokes, or have a family history of cancer and you experience persistent cough, you should ask for a chest X-ray. A chest CT is more helpful in order not to overlook a very slight lesion.
6-2. Pulmonary tuberculosis
Pulmonary tuberculosis is increasing in recent years.
Pulmonary tuberculosis, or TB, is not a disease of the past. In fact, TB has been on the rise among the elderly and people in the urban areas. The number of new TB patients is approximately 30,000 in the past year and it is an issue which cannot be ignored. Typical symptoms of TB are cough and fever which are quite similar to that of a cold, and it sometimes trigger an outbreak because the symptoms may be confused with other diseases and it delays treatment. Therefore, we conduct sputum smear or sputum culture examination in addition to a chest X-ray if TB is suspected.
7. Other triggers of cough
There are other causes which trigger coughs.
7-1. Side effect of antihypertensive drug
An antihypertensive drug called ACE (angiotensin-converting enzyme) inhibitors, which is typically used for high blood pressure treatment may cause cough. ACE inhibitor is among the best antihypertensive drugs which is widely used for patients with cardiovascular disease and considered a highly effective medication. However, patients need to undergo a medication change in cases where the ACE inhibitor triggers a cough. This does not happen to every patient and occurs only in a few percent of all cases.
7-2. Bronchial asthma
Among the patients who complain of persistent cough, some are diagnosed with branchial asthma. They assume that they have either a common cold or hay fever, not a sign of bronchial asthma, so that they leave the symptom untreated. The most characteristic symptoms are coughing and wheezing; the symptom attack often interferes with sleep and does not usually appear when patients visit their physicians in the daytime or in the evening.
There must be a cause when you have persistent cough for long periods of time. Remember that adult-onset asthma is one of the possible causes of persistent cough.
7-3.Smoking
I often see smokers who keep coughing. A study shows that more than 25% of smokers who smoke more than 10 cigarettes a day result in developing a chronic cough. It is also said that more than 50% of smokers who smoke more than 40 cigarettes develop a chronic cough. However, there seems to be few smokers who visit their physicians even when they suffer from chronic cough.
8. Summary
- A persistent cough may be triggered by causes other than respiratory diseases.
- Most coughs disappear on their own.
- Medical care is needed if cough is present more than three weeks.