What is cough-variant asthma?
Cough-variant asthma is a type of asthma in which the main symptom is a dry, non-productive cough. (A non-productive cough does not expel sputum from the respiratory tract.) People with cough-variant asthma (or CVA) often have no other “classic” asthma symptoms, such as wheezing or shortness of breath.
Cough-variant asthma is sometimes called chronic cough to describe a cough that has lasted longer than six to eight weeks. Coughing with asthma can occur during the day or at night. If you have night-time asthma, it can interrupt sleep. People with cough-variant asthma often notice that coughing increases with exercise, called exercise-induced asthma. Coughing may increase when they are exposed to asthma triggers or allergy-causing substances like dust or strong fragrances, or when they are in cold air.
Who gets cough-variant asthma?
Anyone can get cough-variant asthma at any time, but it is common in young children with childhood asthma. Cough-variant asthma may lead to the development of “classic” asthma, with symptoms that include shortness of breath and wheezing.
What causes cough-variant asthma?
Like “classic” or “typical” asthma, no one really knows what causes cough-variant asthma. However, coughing may start after people are exposed to allergens, or when they are breathing in cold air. Coughing may also follow an upper respiratory infection. For example, sinusitis with asthma is common.
In addition, a cough that begins after a person has begun taking beta-blockers is likely to be cough-variant asthma. Beta-blockers are drugs used to treat high blood pressure, heart disease, heart failure, migraines, palpitations, and other conditions. Beta-blockers are also found in eye drops to treat glaucoma. These eye drops can bring on asthma symptoms, including cough. Asthma and aspirin-sensitivity is another cause of coughing with asthma.
How is cough-variant asthma diagnosed?
Cough-variant asthma is somewhat difficult to diagnose because the cough may be the only symptom, and the cough itself may appear to be bronchitis or a cough associated with postnasal drip.
Your GP will ask you questions about your medical history and will examine you and listen to you breathe. However, people with cough-variant asthma often have normal physical examinations, chest X-rays, peak flow measurements and spirometry. Spirometry involves measuring how much air you can exhale after first taking a deep breath, and how quickly you can empty your lungs. The asthma test uses a device called a spirometer to do the measuring.
A methacholine challenge test (also known as a histamine challenge test) will indicate asthma, but it may require the use of a special facility. This test may be performed if your symptoms and spirometry test do not clearly show asthma. When inhaled, methacholine causes the airways to spasm and narrow if asthma is present. During the test, you inhale increasing amounts of methacholine aerosol mist before and after spirometry. The methacholine test is considered positive - meaning that asthma is present - if the lung function drops by at least 20 per cent. A bronchodilator (airway-opening drug) is always given at the end of the test to reverse the effects of the methacholine.
Another way to diagnose cough-variant asthma involves treatment. The GP may choose to give the patient standard asthma treatments. If the cough responds to these types of treatments, a diagnosis of cough-variant asthma can be made.
How is cough-variant asthma treated?
Cough-variant asthma is treated in the same way that typical asthma is treated. You may be given an asthma inhaler with salbutamol, ipratropium, and/or inhaled steroids (anti-inflammatory agents). You should see a gradual improvement in asthma symptoms over six to eight weeks.