Cough is a natural reflex action that helps to clear the airways from irritants and mucus. While an occasional cough is normal and harmless, a cough that persists for an extended period can indicate an underlying medical condition requiring proper evaluation and treatment. A chronic cough is defined as a cough that lasts for more than eight weeks and often lasts for months or even years. It can significantly impact an individual’s quality of life, causing physical, emotional, and social consequences. The constant interruption of sleep due to cough can lead to fatigue, impaired concentration, and reduced work productivity. Additionally, the forceful expulsion of air during coughing can lead to complications such as urinary incontinence, fainting, and even broken ribs in severe cases. Furthermore, coughing can strain social interactions, particularly in the context of contagious respiratory illnesses, causing embarrassment and anxiety.
Chronic cough represents a significant health burden in the United Kingdom. According to research, 6.2% of the UK population experiences chronic cough at some point in their lifetime. Notably, older adults aged 65 years and above exhibit a prevalence of 6.4%. Furthermore, individuals with current or former smoking habits demonstrate an elevated prevalence of 6.3%, reflecting the detrimental effects of tobacco exposure on respiratory health.
It is important to recognise that chronic cough is not merely a symptom but a condition that warrants comprehensive medical attention. Failure to address a persistent cough can lead to further complications and a diminished overall quality of life. This article will discuss the causes of chronic cough and various effective treatment approaches that can help to improve this condition.
What are the causes of chronic cough?
There are various causes of chronic cough. Smoking represents a significant contributing factor to the development of chronic cough. The toxic chemicals present in tobacco smoke act as irritants, leading most cigarette smokers to develop a persistent “smoker’s cough.” However, the harmful substances responsible for this cough also increase the risk of more severe respiratory conditions, such as COPD, pneumonia, and lung cancer. Consequently, a chronic cough in smokers is a cause for concern, as it may indicate the manifestation of these underlying respiratory diseases.
While chronic cough is often associated with smoking, it is also a concern for non-smokers. Fortunately, for the non-smoking population, most cases of chronic cough are attributed to less severe underlying conditions. These include postnasal drip, asthma, gastroesophageal reflux disease (GERD), and certain respiratory infections. However, regardless of the cause, persistent cough can lead to significant negative consequences, such as worry, embarrassment, exhaustion, and impaired quality of life. This highlights the importance of proper diagnosis and treatment to address chronic cough effectively, regardless of its underlying aetiology.
Major causes of chronic cough
While numerous conditions can contribute to a chronic cough, the majority of cases are attributable to five primary causes:
Postnasal drip: Postnasal drip, also known as the upper airway cough syndrome, is a leading cause of chronic cough. It occurs when excess mucus from the nasal cavity drips down the throat, triggering a cough reflex. This condition can arise from various factors, including viral infections, allergies, sinusitis, and environmental irritants.
The nasal membranes play a crucial role in air conditioning by warming, moisturising, and filtering it. However, when these membranes become irritated due to viruses, allergens, dust particles, or airborne chemicals, they produce excessively thin, watery mucus. As this mucus drips down the throat, it can stimulate the nerves in the nasopharynx, triggering a persistent cough. Patients with postnasal drip often experience increased coughing at night and may be aware of a tickling sensation at the back of their throats. However, coughing can also occur during the day, and the throat may or may not be irritated or sore.
A trial of treatment is often given to determine if postnasal drip is the cause of a chronic cough. Non-prescription decongestants or antihistamines, containing either or a combination of these medications, can be an initial step. Home remedies include inhaling steam from a hot shower or kettle or nasal saline irrigation, which involves flushing the nasal passages with a saline solution. If found effective, this irrigation process can be repeated thrice daily. These remedies help soothe the nasal passages and alleviate the chronic cough associated with postnasal drip.
Asthma: Asthma is a long-term inflammatory disease that affects the airways in your lungs. It can present itself in several forms, one of which is known as cough-variant asthma. Unlike typical asthma, which is often characterised by wheezing and shortness of breath, cough-variant asthma primarily manifests as a persistent, dry cough. In asthma, the airways in the lungs can temporarily constrict due to a phenomenon known as bronchospasm. This constriction can cause a wheezing sound as air struggles to pass through the narrowed passages. However, in the case of cough-variant asthma, the coughing may be the sole symptom, without the presence of wheezing or breathlessness.
Physicians may order pulmonary function tests to diagnose asthma as the underlying cause of a chronic cough. If these tests are inconclusive, a methacholine challenge test may be performed, where the patient inhales a small dose of methacholine, a drug that can induce bronchospasm and wheezing in individuals with asthma.
Gastroesophageal Reflux Disease: It’s a condition where stomach contents, including acid, flow back from the stomach into the oesophagus. While heartburn is the most common symptom, GERD can cause chronic cough without the typical reflux symptoms. The acid that refluxes into the oesophagus can irritate the nerves in the oesophagal lining, triggering the cough reflex. In fact, up to one-third of patients with GERD experience cough as their primary symptom without the characteristic heartburn or other reflux-related discomforts.
Diagnosing GERD-related cough can be challenging when pain is not present. Oesophageal pH monitoring may be necessary, where a probe is swallowed and remains in the lower oesophagus for 24 hours to detect the presence of acid reflux. However, this method is expensive and inconvenient.
As with other causes of chronic cough, a trial of treatment is often a more straightforward approach to diagnosis. It may involve lifestyle modifications, such as avoiding triggers like alcohol, chocolate, peppermint, caffeine, garlic, onions, citrus fruits, tomato sauce, or fatty foods. Eating smaller meals, avoiding lying down for two hours after eating, taking liquid antacids (particularly at bedtime), and elevating the head of the bed or using a wedge-shaped pillow to prevent reflux at night can also be beneficial.
Chronic Bronchitis and bronchiectasis: Chronic bronchitis is characterised by persistent inflammation of the bronchial tubes, leading to airway narrowing and excessive mucus production. It is often caused by tobacco use or long-term exposure to high levels of industrial air pollutants. Conversely, bronchiectasis is a condition where chronic inflammation damages the walls of the bronchial tubes, resulting in permanent widening and distortion.
In both conditions, the underlying inflammation leads to a chronic cough. Effective treatment involves smoking cessation, avoiding air pollutants, and potentially using inhaled corticosteroids and long-acting bronchodilators. Individuals with chronic bronchitis are prone to exacerbations or flare-ups, characterised by increased coughing, thick, discoloured mucus production, shortness of breath, and fatigue. Management of these exacerbations typically involves antibiotics and oral corticosteroids, such as prednisone.
Angiotensin-converting enzyme (ACE) Inhibitors: ACE inhibitors, such as enalapril and lisinopril, are widely used to treat hypertension and heart failure. However, a persistent, dry cough is a well-known side effect of these medications.
The cough often begins with a mild throat tickle and progresses to a persistent, dry cough, which can develop within three weeks to one year after initiating ACE inhibitor therapy. Once established, the cough tends to linger. While some patients may tolerate a mild cough and continue the medication, switching to an alternate antihypertensive medication such as angiotensin-receptor blockers or calcium channel blockers is the only effective solution for severe persistent cough.
Several other less common underlying conditions can also contribute to persistent cough. These include airborne environmental irritants, aspiration during swallowing, heart failure, lung infections, pertussis (whooping cough), lung cancer, other lung diseases, and psychological disorders. It is important to note that many individuals may have multiple coexisting conditions contributing to their chronic cough. Proper diagnosis, involving a comprehensive evaluation and identification of the specific underlying causes, is crucial for effective treatment and management of this persistent and debilitating condition, regardless of the patient’s smoking status.
When to see a cough specialist?
Chronic cough is a prevalent and potentially debilitating condition that can significantly impact an individual’s quality of life. While numerous underlying causes exist, the most common causes include postnasal drip, asthma, gastroesophageal reflux disease, chronic bronchitis/bronchiectasis, and ACE inhibitors.
Treatment strategies are tailored to the identified cause and may involve a combination of lifestyle modifications, medications, and other interventions. For instance, in cases of postnasal drip, nasal irrigation, decongestants and antihistamines may be recommended. Asthma-related cough may be managed with bronchodilators, inhaled corticosteroids, and avoidance of triggers. GERD-related cough often responds well to acid suppressants like proton pump inhibitors and lifestyle changes like dietary modifications and weight loss. In chronic bronchitis or bronchiectasis cases, smoking cessation and avoidance of air pollutants are crucial, along with the potential use of inhaled corticosteroids and bronchodilators. For ACE inhibitor-induced cough, switching to an alternative medication from a different class may be necessary to alleviate the persistent cough.
Proper diagnosis and targeted treatment are essential for resolving chronic cough and alleviating the associated physical, emotional, and social consequences. A respiratory specialist can comprehensively evaluate your condition, identify potential respiratory disorders, and provide personalised treatment plans tailored to your needs.
As a leading sleep and respiratory consultant specialising in chronic cough and breathing disorders, I offer consultations to diagnose and treat these conditions. Please contact me if you have any further queries about chronic cough or want further advice on the potential treatments available.
