Chronic Cough has many causes. Some can be linked to respiratory diseases or conditions, and some causes require a little detective work by medical professionals to find possible underlying triggers.
In this blog we will explore respiratory conditions of the upper and lower airways that can cause chronic cough, with an overview of how to diagnose and treat these causes.
Upper Airway Conditions that Can Cause Chronic Cough
Several conditions can be responsible for chronic cough in the upper airways:
Upper airway cough syndrome (UACS)
Upper airway cough syndrome (UACS) is the most common cause of chronic cough as defined by the American College of Physicians. UACS is responsible for at least 70 percent of chronic cough in adults. Patients describe it as an abnormal sensation arising from the throat causing them to cough.
Inflammation
Inflammation caused by problems such as rhinitis, laryngitis and chronic sinusitis (inflammation in the nose, throat or sinuses) have all been linked to a persistent cough. Inflammation and production of secretions can be the result of inhalation of an allergen or from an unknown cause that will then stimulate the cough receptors in the upper airways.
Functional problems
An example of a functional problem is dysfunctional breathing. As an example, patients can have a closure of the vocal cords following some external stimulation such as exercise causing them to cough.
Environmental factors
Environmental factors can trigger chronic cough in people who have a cough hypersensitivity. Exposure to external stimulation such as dry air will cause a cough because the many cough receptors in their upper airways are already more sensitive.
Diagnosis
When diagnosing upper airway conditions linked to chronic cough physicians can look at:
- Symptoms: one of the first steps should be to record the patient’s symptoms. Post-nasal discharge, sneezing and nasal congestion are often associated with rhinitis or even nasal polyps. Allergic or non-allergic rhinitis symptoms can be easily observed and recorded.
- Endoscopy: is performed by an ENT specialist. It requires inserting a thin flexible tube with a camera on the end into the nose to look for inflammation and polyps.
- Laryngoscopy: is also performed by an ENT specialist. A thin flexible tube with a camera is inserted through the mouth to see if there is an abnormal closure of the vocal cords (like for example, during exercise).
- Sinus x-ray: signs of a chronic sinusitis can be seen on a sinus x-ray.
Lower Airway Conditions that Can Cause Chronic Cough
Lower airway conditions are the second most common cause of chronic cough. Among those conditions we find:
Asthma
Asthma touches about ten percent of our population, so it is a frequent cause of persistent cough. However, usually along with coughing, asthma causes other variable symptoms like wheezing and shortness of breath. It can also be induced by exercise or environmental factors/allergens.
Chronic Obstructive Pulmonary Disease (COPD)
COPD, most often found in long term smokers can result in a chronic cough or what we call a smoker’s cough. COPD symptoms are more fixed over time and can include wheezing and shortness of breath as well.
Other important causes to identify
Sometimes chronic cough is a symptom of a tumor or cancer in the lower airways. Lung cancer is possible at any age with or without a history of smoking or environmental exposure.
Diagnosis
It has been shown that there is a lot of under and over diagnosis of lower airway conditions. There are several tests available to diagnose asthma, COPD, and lower airway malignancies:
- Breathing test before and after a bronchodilator demonstrates if there’s an airway obstruction, and if it is reversible or partially reversable after administrating a bronchodilator. A significant response to a bronchodilator is suggestive of asthma. A non-reversible airway obstruction is more often associated with COPD.
- Methacholine challenge: also called a bronchoprovocation test, measures how reactive or responsive the airways are to an inhaled substance causing asthma symptoms. It can be requested if breathing test are normal but based on the clinical picture, asthma is still suspected.
- Exercise test: exercise-induced asthma can be diagnosed with an exercise test, as narrowing of the airways in response to exercise can be observed, but if symptoms occur after exercise and another test (e.g., methacholine) shows an increase responsiveness of the airways, exercise-induced asthma can be confirmed.
- FENO: or fractional exhaled nitric oxide measurement is used to measure the amount of nitric oxide in exhaled breath. Increasing levels of nitric oxide could indicate inflammation in the airways caused by asthma.
- CT scan/chest x-ray: a CT scan or chest x-ray can help doctors diagnose or eliminate other causes of cough like bronchiectasis or tumors.
Treating Chronic Cough
Treating chronic cough really depends on determining the cause whether it be relation to upper or lower airway conditions.
Upper Airway Conditions
If chronic cough is associated with upper airway conditions some suggested treatments available are:
- Avoiding allergy or environmental triggers. For example, things like pollution, pet dander (if allergic) and dry air.
- Using antihistamines (drugs to treat allergies) or nasal sprays suggested or prescribed by your doctor.
- Medication or surgery for nasal polyps.
- Prescribed medications to block cough receptors.
Lower Airway Conditions
Treatments for lower airway conditions will depend on identifying the cause. Some treatments include:
- Inhaled corticosteroids are the basic treatment for asthma. Depending on the type of asthma corticosteroids can be taken in combination with long-acting bronchodilators, for maintenance/preventative treatment.
- Biologics are given in the case of severe asthma when mainstay treatments are not effective. They are however very expensive.
- Bronchodilators (beta-agonists or anticholinergics) are the basic treatment for COPD (Chronic Obstructive Pulmonary Disease).
- Non-pharmacologic treatments encompass avoiding triggers like allergens and pollution, living in a smoke-free environment and keeping healthy lifestyle habits (nutrition, physical activity, stress management).
The Key Message
When looking at the relationship between chronic cough and various respiratory conditions, the key message is that a diagnosis must be confirmed to identify underlying causes. Pulmonary function tests are a must. If the results are insufficient or inconclusive, then other tests and referrals to specialists are needed.
To learn more about chronic cough please go and read our latest report:
https://chroniclungdiseases.com/en/resources/chronic-cough/
- (1) Chronic Cough: Resourses - Chronic Obstructive Pulmonary Disease
- (2) Upper airway cough syndrome (UACS) : BMJ Best Practice
- (3) Dysfunctional breathing / a review of the literature and proposal for classification : European Respiratory Society
- 4) Fractional exhaled nitric oxide measurement : AAFA
About the author
Katrina Metz is currently working as a consultant for RESPIPLUS, striving to improve education in the respiratory domain for healthcare professionals and patients alike. She has over 16 years experience working as a respiratory therapist and clinical research coordinator for the Research Institute of the McGill University Health Center.
