Coughing is one of those things we do for a variety of reasons.
It can be a social thing, where we cough to get attention; or it could be psychological, where we do it to clear our throats prior to speaking in public.
But most often, we cough in response to something irritating our respiratory system, which includes the throat and the lungs.
This is most likely due to either an irritant in our environment, like smoke or the haze, or a respiratory infection like the cold or flu.
Says consultant physician and respiratory specialist Dr Kow Ken Siong: “Cough is not necessarily bad, to be honest, because the cough reflex is actually there to protect us. It is designed to keep foreign particles out of our airways, so it’s not always a bad thing.
“But of course, if it is very persistent and affects the quality of life of patients, obviously, we need to find out why this person is coughing incessantly.”
Most patients, he says, tend to see the doctor when their cough has lasted between three to eight weeks, also known as a subacute cough. Any cough lasting more than eight weeks is considered chronic.
Shares Dr Kow: “In terms of cough and/or breathlessness, I think these two symptoms are probably the most common symptoms that patients come to consult with a respiratory physician.
“For example, cough will probably be the main symptom in about half of all our patients. And I would say that even more patients come in with breathlessness.
“And there’s a good amount of patients who come in with both symptoms at the same time.”
For coughs that have been present between three to eight weeks, three conditions usually come to mind, says Dr Kow.
One of them is upper airway cough syndrome.
“This is an umbrella term just to make things easier,” he explains. “For example, upper airway cough syndrome would consist of something very common – post-nasal drip.”
This occurs when someone with rhinitis – which is when the mucous membrane of the nose is inflamed from allergies or infections – experiences excessive mucus accumulating at the back of their nose and dripping down to the throat.
This irritates the throat, resulting in a cough that tries to get rid of the mucus. Other symptoms usually include a stuffy and/or runny nose, sneezing and frequent throat-clearing in an attempt to get rid of the drip.
Another condition with subacute cough is gastroesophageal reflux disease (GERD).
“Generally, these patients will present with heartburn; so, they may complain of a retrosternal burning sensation and a bitter taste behind their tongue,” he says.
“But then again, sometimes, these symptoms might not be present; the only manifestation is actually the dry cough lasting three to eight weeks.”
The other condition a doctor would consider is asthma.
This, Dr Kow says, is “a very common respiratory condition contributes to both symptoms of subacute and chronic cough, and breathlessness”.
He explains: “You can say that asthma is an inflammation of the airways due to triggers, which are particular to each patient.
“There are common triggers obviously, but every individual with asthma may have different triggers, resulting in inflammation of the airways leading to bronchospasm (which causes narrowing of the airways).
“It is this bronchospasm that gives rise to the symptoms of breathlessness and wheezing.”
Asthma typically runs in families as it has a genetic component, so family history of asthma is a strong indicator that the patient’s symptoms are a result of asthma.
While most patients develop asthma in their childhood, it can also first manifest in a patient’s 20s, especially if there is a strong family history of asthma and they become pregnant, as well as in their 40s or 50s, although these patients would have to be carefully examined to exclude chronic obstructive pulmonary disease (COPD), which is more common in that age group.
“It is about 20%-25% of patients who develop adult-onset asthma, and it is more common in females,” says Dr Kow.
Some childhood asthma patients who have outgrown their asthma may also find that it returns when they are adults.
Those with no family history of asthma may develop the condition due to environmental triggers like exposure to certain chemicals in childhood, or the body’s own immune response to respiratory infections, that both help to prime the respiratory system to develop asthma.
According to Dr Kow, patients usually experience cough and/or shortness of breath at night or early in the morning.
He notes that exercise can also bring on shortness of breath and coughing, along with chest tightness, and sometimes, wheezing. These symptoms usually start around three minutes after starting to exercise.
For coughs that last longer than eight weeks, Dr Kow divides up the possible causes into diseases of the airway and diseases that affect the lung parenchyma – the “meat” of the lung.
Diseases of the airway include bronchiectasis – the abnormal, irreversible dilatation of the bronchi with bronchial wall thickening due to previous infection and inflammation – and COPD.
For COPD, Dr Kow notes that there is usually a very strong history of smoking at least one pack a day for a minimum of 20 years.
In addition, he says that while asthma patients may have good days where they do not have any symptoms at all, COPD patients never have such days, only times when their symptoms might be less bothersome.
Another airway disease is foreign body aspiration into the lung, leading to infection.
Says Dr Kow: “When a patient comes in with cough, if you don’t ask them, sometimes, they may not tell you that they tend to choke when they eat or drink, especially the elderly.
“So, we’re more likely to see these sort of symptoms due to foreign body aspiration in the elderly and those who have underlying co-morbidities, for example, if they have had strokes before or radiotherapy treatment to their upper airways, affecting their swallowing ability.”
He adds that the aspirated foreign body need not necessarily be a big piece of food, but could be something small that often goes unnoticed, for example, a grain of rice, or even water.
Lung tumours can also cause chronic coughing.
However, Dr Kow says: “To be honest, they are responsible for symptoms like cough and shortness of breath less than 5% to 10% of the time.”
More common symptoms of a lung tumour would be weight loss, loss of appetite and coughing up blood (haemoptysis). A history of smoking is also quite common.
Meanwhile, among the diseases that affect the lung parenchyma resulting in chronic cough is interstitial lung disease.
This disease, which affects the tissue and space around the air sacs of the lungs (the interstitium), tends to cause a dry cough and shortness of breath that gets worse with time.
“One of the more common interstitial lung diseases that can cause these symptoms is pulmonary fibrosis, of which idiopathic pulmonary fibrosis is the most common,” he says, adding that these patients tend to be in their 70s and male.
Another condition is a lung abscess.
“It’s not so common, but if patients present with shortness of breath and cough with a productive sputum, which tends to be quite mucopurulent (pus-like) and foul-smelling, and if they’ve had an underlying lung infection prior to this, a pneumonia for example, then you might suspect a lung abscess if the pneumonia didn’t heal well,” he says.
Finally, Dr Kow says that there is the 10% of patients with cough in whom, despite proper history-taking, physical examination and investigation, no cause can be found for the cough.
“We will probably categorise these patients as having idiopathic chronic cough,” he says, adding that this is more likely in females as it is hypothesised that females tend to have a more sensitive cough reflex, compared to males.