What is Chronic Cough?
Coughing is a complex reflex action where various muscles and neural pathways work together. Its main purpose is to protect our breathing system by clearing foreign materials that could be harmful or disrupt normal breathing. Although coughing is generally a good thing, ongoing or long-term coughing can indicate an underlying health problem and may need further investigation and treatment.
Coughs can be classified into three categories: acute cough (lasting less than 3 weeks), subacute cough (lasting 3 to 8 weeks), and chronic cough (lasting more than 8 weeks in adults). Chronic cough is a common yet often overlooked condition that can significantly impact a person’s quality of life. It can sometimes pose a diagnostic challenge for doctors as it may be a symptom of both commonly known and lesser-known diseases.
This overview will mainly focus on chronic cough, discussing its causes, how common it is, its symptoms, how it’s diagnosed, and how it’s managed.
What Causes Chronic Cough?
Chronic cough can be a sign of a variety of conditions, both related and unrelated to the respiratory system.
Asthma is one potential cause, with cough-variant asthma being a type where coughing is the only symptom. This is because the airways become overly sensitive to certain triggers, leading to episodes of coughing which can be persistent day or night. Professionals often use breathing tests, like spirometry, to diagnose this type of asthma.
Nonasthmatic Eosinophilic Bronchitis (NAEB), which shares similar characteristics with asthma, can also cause chronic cough. In this condition, inflammation occurs in the bronchial tubes but without the inconsistent airflow obstructions seen in asthma. People with reoccurring NAEB are at a greater risk of developing asthma later on.
Chronic Bronchitis, a common type of Chronic Obstructive Pulmonary Disease (COPD) caused by smoking, is another notorious contributor to chronic cough. People tend to ignore their cough due to the condition developing over time and just incorporating it into their daily life. However, any change in the cough should be checked out for more severe issues like lung cancer.
Gastroesophageal Reflux Disease (GERD) can also induce cough through direct and indirect mechanisms related to stomach acid’s effects. Stomach acid can irritate the esophagus and laryngopharyngeal areas, which would trigger a protective cough reflex. It can also irritate the vagus nerve, leading to reflex coughing.
Upper Airway Cough Syndrome (UACS), previously known as postnasal drip syndrome, is a significant contributor to chronic cough. The mechanisms behind the cough involve various factors like mucus drip and inflammation in the upper and lower airways.
Certain medicines, particularly angiotensin-converting enzyme (ACE) inhibitors used for high blood pressure and heart failure, can cause a dry cough as a side effect. Gastroesophageal reflux (GER)-increasing medications and some eye drops used for glaucoma can also contribute to a cough.
Bronchiectasis is a chronic cough cause where the bronchi, the airways leading to your lungs, are abnormally widened. This condition typically expresses itself through a persistent cough that produces sputum or phlegm.
Respiratory infections like common colds typically cause a cough. If the cough reflex becomes hypersensitive, it can still last for weeks or longer after the infection has cleared. Those with respiratory infections caused by certain pathogens like the COVID-19 virus often show increased cough cases.
Tumors or cancers in the respiratory system can lead to a persistent cough. The irritation or obstruction of the airways caused by these can trigger a cough reflex.
Interstitial Lung Disease (ILD) such as idiopathic pulmonary fibrosis (IPF) often present cough as a common symptom. It may arise due to mechanical distortion from scarring and damage to lung tissues, gastric content’s backflow irritating the airways, or inflammation within the airways.
In some instances, the cause of a chronic cough is unknown, even after testing and treatment, and is considered idiopathic. In these cases, an autoimmune process in the lung might be the cause.
Risk Factors and Frequency for Chronic Cough
Chronic coughing is a common issue worldwide, affecting between 3% to 18% of adults. This condition can be influenced by various factors, including smoking habits and age. For instance, 18% of adult smokers in the U.S. experience chronic coughing. The frequency of this condition differs across regions and isn’t related to ethnicity or genetics. For example, chronic coughing is more common in Europe and America than in Asia and Africa, possibly due to differing environmental conditions, such as greater urbanization and exposure to irritants in the air in Western countries.
Research shows that the likelihood of chronic coughing increases with age. Notably, a study has shown that individuals aged 65 and above are more than twice likely to have a chronic cough than those aged between 18 to 39 years. This trend aligns with findings from various studies suggesting that chronic cough becomes more frequent in older people. Continued exposure to environmental factors over time could be a contributing factor. Interestingly, one study found no notable differences in cough reflex sensitivity – how easily someone coughs – among different ethnic groups, implying that racial variations in chronic cough prevalence can’t be attributed directly to differences in cough reflex sensitivity.
Beyond age and smoking, chronic coughing can also be influenced by obesity, allergies, asthma, COPD (a type of lung disease), GERD (a type of digestion disorder), usage of ACE inhibitors (a type of blood pressure medication), and sleep-related breathing issues. Although the link between air pollution/quality and chronic coughing prevalence isn’t strong, exposure to metals has positively correlated with an increased prevalence.
Signs and Symptoms of Chronic Cough
Assessing a persistent cough includes a detailed personal history and physical exam. Key stages of this evaluation involve mapping out the characteristics of the cough such as how long it’s been present, whether it’s bringing up mucus (productive) or not (nonproductive), and any additional symptoms. Other symptoms can include a runny or blocked nose (rhinorrhea), nasal congestion, sneezing, fever, production of mucus (sputum), coughing up blood (hemoptysis), shortness of breath (dyspnea), weight loss, hoarse voice (dysphonia), difficulty swallowing (dysphagia), and a distinctive, severe, hacking cough followed by a high-pitched intake of breath that sounds like ‘whoop’.
Knowing if the patient or their family has had allergies or respiratory issues previously is important. Smoking, being exposed to smoke from electronic cigarettes, and being exposed to certain substances from work or recent travel could explain the chronic cough and increase the chances of developing serious lung conditions like chronic bronchitis and lung cancer.
The evaluation should also involve asking about any medications that the patient is on, as some can result in a persistent cough. The most common reasons for a persistent cough in adults include asthma, upper airway cough syndrome (UACS), and gastroesophageal reflux disease (GERD), so it’s crucial to watch out for symptoms related to these conditions.
In some cases, you might experience a condition called silent UACS where the only symptom is a cough, usually caused by nose and sinus conditions. This can lead to a light feeling of irritation in the back of the throat and upper airways and postnasal drip (mucus dripping down the throat from the back of the nose). On examining the throat doctors may observe inflammation (pharyngitis) and a “cobblestone” appearance. Sometimes, these conditions may cause no other symptoms, so the cough might be the only sign of their presence and seem more pronounced. Silent UACS diagnosis usually comes after treatment based upon these findings brings significant relief.
Last but not least, it’s essential to pick up on any dangerous signs urgently and consider chronic infections such as tuberculosis, lung abscess, or rheumatologic diseases if the patient is experiencing fever, night sweats, or weight loss. The presence of dark yellow or greenish mucus (purulent sputum) should be investigated further. Coughing blood could indicate infections like bronchiectomy (widening of the airways), lung abscess, tuberculosis, cancer (of the lung, bronchi or larynx), rheumatism, heart failure, or having breathed in an object.
If the patient also experiences difficulty breathing (dyspnea), it could indicate airway blockage (laryngeal, tracheal, bronchial, bronchiolar), or disease of the air sacs in the lungs (lung parenchymal disease). Other details, such as if the symptoms come and go versus steadily getting worse, specific triggers, associated hoarseness, and peculiar abnormalities found during the physical exam, can help narrow down the cause of the chronic cough.
Testing for Chronic Cough
If you have a cough that’s been going on for a long time, it is important that a doctor takes a structured approach to find out what’s causing it. This usually starts with tests like a chest x-ray and pulmonary function tests – which measure how well your lungs are working.
Having a chest x-ray is generally recommended for adults who’ve had a cough for more than eight weeks. But there could be exceptions, such as if the main suspected reasons for the cough are conditions like asthma or UACS. In these cases, doctors might start treatment right away without an x-ray.
CT scans of the chest are not usually needed if the results of a chest examination and x-ray look normal. However, they might be used for checking other things that might not be visible on a regular x-ray or if something unusual shows up.
In people with a long-term cough, particularly those who have smoked a lot, doctors might decide to do a CT scan more readily because of an increased risk of lung cancer.
Pulmonary function tests can also help doctors figure out if asthma or COPD (a lung disease that makes it hard to breathe) could be causing the cough. If these tests don’t show anything, doctors might consider other tests to see if the airways react unusually to things like methacholine or histamine, although how useful this is, is sometimes questioned.
Current guidelines recommend certain techniques for measuring inflammation in the airways when assessing and managing a cough related to asthma. For example, evidence of ongoing inflammation can be checked by looking at cell counts from samples of induced sputum or bronchoalveolar lavage. If these show increased levels of particular inflammation cells (eosinophils), it could suggest a condition called eosinophilic bronchitis.
However, the usefulness of measures like fractional exhaled nitric oxide or blood eosinophils in diagnosing or guiding treatment for people with a chronic cough has yet to be fully evaluated in the clinic and more quality research is needed.
Finally, if a cough lasts more than three weeks without an obvious cause and treatments haven’t worked, it may be considered an idiopathic chronic cough. Sometimes, this is accompanied by increased lymphocytes (a type of white blood cell) in the fluid from a bronchoalveolar lavage.
Treatment Options for Chronic Cough
Patients who are given an ACE inhibitor, which is a type of blood pressure medication, may see improvements if they switch to another type of drug. If a patient is suspected of having UACS (Upper Airway Cough Syndrome), it’s helpful to use saline rinses, an old-style antihistamine, and nasal steroids.
No clear evidence shows that taking specific medications (such as antibiotics, bronchodilators, or mucolytics) helps adults with chronic cough due to chronic bronchitis.
If GERD (Gastroesophageal Reflux Disease) is a potential cause, the patient should try dietary changes, lifestyle modifications, antacids, and medications known as proton pump inhibitors for 3 months before undergoing a test that measures stomach acid in the esophagus. If tests reveal a high number of a type of white blood cell called eosinophils in the mucus/sputum or in a sample of fluid from the lungs (BAL), inhaled steroids can help treat NAEB, a type of asthma causing cough.
Some people might have more than one reason for their persistent cough, especially those who visit specialized clinics. It’s essential to recognize and deal with all the possible triggers at the same time for the cough to be fully resolved.
People with a chronic cough caused by asthma can be treated the same way as those with regular asthma. Inhaled corticosteroids, which are medications to reduce inflammation in the airways, are usually the first choice of treatment. If the symptoms don’t entirely disappear with this treatment, increasing the dose or trying a leukotriene inhibitor (another type of medication to reduce inflammation) could be considered.
There are some different choices for treating a chronic cough that doesn’t have a known cause, including drugs called opioids and some non-opioid medications. A study showed that a low dose of slow-release morphine (a type of opioid) helped reduce cough severity more than a placebo (a substance with no effect, given as a control in studies). Other non-opioid medications like gabapentin or pregabalin have also been found helpful in improving the quality of life for those with persistent, hard-to-treat coughs.
The most recent guidelines provide various treatment recommendations for chronic cough, depending on the cause. For asthma, inhaled corticosteroids are the preferred first step. For NAEB, inhaled corticosteroids are the first treatment option. If the patient doesn’t show enough improvement, the dose can be increased, and additional therapy may be considered.
For GERD, there’s limited evidence that medications to reduce stomach acid are useful, especially if there isn’t acid reflux. For UACS, corticosteroids or antihistamines are recommended at first. If the cough has no known cause, a dose of morphine can be beneficial, or gabapentin or pregabalin can be tried.
Non-medication treatments like physical therapy and speech/language therapy are often recommended for adults with chronic cough. Studies have shown that these methods can significantly reduce the severity of cough and improve quality of life.
What else can Chronic Cough be?
When a person has a chronic cough, there are many different possible causes that a doctor might consider. These include:
- Bronchiolitis (an inflammation of the small airways in the lungs)
- Bronchogenic carcinoma (a type of lung cancer)
- Chronic aspiration (regularly inhaling food, drink, or stomach acid into the lungs)
- Congestive heart failure (a condition where the heart doesn’t pump blood as well as it should)
- Foreign body in the airway (when an object is accidentally inhaled into the windpipe or lungs)
- Neuromuscular disorders (conditions that affect the nerves that control your voluntary muscles)
- Psychogenic cough (a cough that’s related to a psychological issue)
It’s crucial for doctors to evaluate these possibilities thoroughly to make an accurate diagnosis.
What to expect with Chronic Cough
Coughing is more than just a symptom; it can actually be a sign that a disease is getting worse. This is particularly true for patients with idiopathic pulmonary fibrosis (IPF), a condition that affects the lungs. A study of 242 patients with IPF found that coughing was linked to the disease getting worse, no matter how severe the disease was to begin with. Interestingly, patients with more advanced forms of lung fibrosis (scarring) were found to cough more often.
But it’s not enough to simply note the presence of a cough. It’s important to figure out whether the cough is due to the inflammation or scarring from the disease itself, or if it might be due to another health issue.
In a more recent study, researchers found that many people diagnosed with chronic coughing – a persistent cough that lasts for at least 5 years – kept on coughing for that long. This was slightly more upbeat than an earlier study, which had found that 60% of patients saw their coughing symptoms get worse or stay the same after 7 years.
The difference in these study results could be due to the different groups of patients who were studied. The first study only studied patients with unexplained, or “idiopathic”, chronic cough. The most recent study looked at people with various conditions that cause coughing, as well as those with idiopathic cough. This might give us a more accurate picture of what’s happening among the general population of chronic cough patients.
One thing to note is that in this most recent study, there was a high number of patients with autoimmune diseases, conditions where the body’s immune system attacks its own cells. This is a common characteristic in patients with idiopathic chronic cough. Most patients with asthma and chronic rhinitis (runny nose) were successfully managed with local steroid creams or antihistamines. Unfortunately, most patients with reflux disease didn’t get treatment with proton pump inhibitors, which is not a successful treatment for cough associated with reflux disease.
The researchers also found that overweight and obesity could predict ongoing issues with coughing affecting quality of life. Specifically, people who qualified as obese were at a higher risk for continued cough-related problems.
Possible Complications When Diagnosed with Chronic Cough
If not properly addressed, a persistent cough can cause various problems that greatly affect your quality of life. Having long periods of coughing can lead to physical tiredness, interrupted sleep, and increased stress, all of which can harm your overall health and happiness. Frequently coughing can also cause muscle issues like chest pain and sore abdominal muscles. Socially, a relentless cough can lead to embarrassment and less social interaction because it disrupts conversations and other group activities. Continuous irritation of the air pathways can also make existing lung conditions worse, possibly resulting in other issues like bronchitis or pneumonia. Also, constant coughing can contribute to stress urinary incontinence, especially in women. Therefore, it’s important to deal with a constant cough through medical help and changes in lifestyle. This can help to prevent these problem and improve overall health and daily activities for people suffering from this relentless condition.
Preventing Chronic Cough
The main goal of strategies to prevent and stop chronic cough is to tackle the root causes and lessen the chance of ongoing breathing troubles. This often includes lifestyle changes like quitting smoking and avoiding exposure to pollution. Information campaigns can really help highlight the dangers of smoking and the benefits of keeping the air in our homes clean.
Having regular check-ups with doctors or nurses can catch and treat breathing problems early, stopping them from turning into a stubborn cough. Getting vaccinated against lung infections that can be prevented is another important step. Moreover, having rules at work that limit contact with dangers in the air can really help keep chronic cough at bay.
Combining individual choices, education for everyone, and medical treatments can help society decrease the impact of chronic coughing on people’s health and healthcare systems. By working together, we can make a big difference.