What Is Cough-Variant Asthma?

Cough-variant asthma is a form of asthma in which the primary symptom is a dry, non-productive cough. The symptoms differ from symptoms of other forms of asthma. Sometimes, cough-variant asthma—especially when not properly treated—is a precursor to "classic" asthma in which shortness of breath, wheezing, and chest pain are accompanied by a wet, productive cough.

Cough-variant asthma can be difficult to diagnose because chronic dry coughing can be attributed to many conditions. But a diagnosis is important because treatment of cough variant asthma is not the same as treatment for other types of chronic coughing.

Cough-Variant Asthma Symptoms

Cough-variant asthma is confusing because it doesn't have many features of asthma. A chronic, non-productive cough is the distinguishing feature, but there are not usually other typical signs or symptoms of asthma.

There are many reasons you could develop a chronic cough, which is defined as a cough lasting more than eight weeks in adults and four weeks in children. The timing of the severe coughing episodes could be a clue that asthma is involved.

Cough-variant asthma should be suspected if:

• Bouts of coughing awaken you from sleep (nocturnal asthma)
• You experience coughing fits after exercise (exercise-induced asthma)
• Coughing worsens in cold, dry weather (cold-weather asthma)
• Hay fever or exposure to dust or pet dander sets off a coughing episode (allergic asthma)

Cause

As with classic asthma, the cause of cough-variant asthma has not been established. In some cases, cough-variant asthma may be an early sign of the onset of classic asthma. Children are more likely to be affected by cough-variant asthma than adults.

There is growing evidence that asthma is part of a continuum of disorders called the atopic march. Atopy, a genetic tendency toward allergic diseases, is believed to develop from early childhood.

• It starts when the immature immune system is exposed to substances that it does not yet recognize as harmless.
• An immune overreaction to these harmless substances can set off a chain reaction in which the immune system progressively regards other substances as harmful.

With that said, not everyone who has cough-variant asthma will develop classic asthma. A 2010 review of studies from Italy suggests that only around 30% of people with cough-variant asthma will go on to do so.

Given it is a milder form of the disease, cough-variant asthma is more likely to resolve on its own by the teen or adult years than moderate persistent or severe persistent asthma.

Prospective studies have also suggested that one of four people with idiopathic chronic cough (cough of unknown origin) have cough-variant asthma.

Diagnosis

Cough-variant asthma can be misdiagnosed, and it is a difficult diagnosis to confirm.

Asthma is mainly diagnosed based on your symptoms, medical history, and a variety of tests that evaluate your lung function. These tests, called pulmonary function tests (PFTs), measure the capacity of the lungs and the force of exhalations after exposure to different substances. Other tests may be considered, as needed.

Pulmonary Function Tests

For adults and children over age 5, the first PFT used is called spirometry. It involves a device called a spirometer into which you breathe so that your forced expiratory volume in one second (FEV1) and forced volume capacity (FVC) can be measured.

Your initial FEV1 and FVC values are then retested after you have inhaled a medication called a bronchodilator that opens the airways. Based on changes in the FEV1 and FVC values, the healthcare provider may be able to definitively diagnose asthma.

There are downsides to spirometry. It cannot be used in younger children whose lungs are still developing and it has a high rate of false-positives results. This makes borderline results much harder to interpret.

If spirometry test results are uncertain with a bronchodilator, another test called a bronchoprovocation challenge may be conducted. For this test, the FEV1 and FVC values are compared before and after exposure to substances or events that can trigger allergy symptoms.

These include:

• Methacholine, an inhaled drug that can cause bronchoconstriction (narrowing of the airways) in people with asthma
• Exercise, which may trigger exercise-induced allergy
• Cold air, which may trigger cold-weather asthma
• Histamine, a naturally occurring substance that may trigger allergic asthma

The problem with bronchoprovocation is that people with cough-variant asthma have less hyperresponsiveness (airway sensitivity) than people with classic asthma and tend to be less responsive to methacholine and other stimuli.

Breath Test

A breath test for exhaled nitric oxide (an inflammatory gas released from the lungs) is highly predictive of cough-variant asthma even if all other tests are inconclusive.

Differential Diagnoses

There are other possible causes of chronic cough in the differential diagnosis that your provider may consider during your evaluation.

This may include:

• Bronchiectasis
• Congestive heart failure
• Chronic rhinosinusitis
• Cystic fibrosis
• Chronic obstructive pulmonary disease (COPD)
• Gastroesophageal reflux disease (GERD)
• Pulmonary embolism
• Vocal cord dysfunction

Treatment

The treatment of cough-variant asthma is virtually the same as for classic asthma. If the symptoms are mild and intermittent, an albuterol inhaler may be all that is needed. If the symptoms are persistent, an inhaled corticosteroid like Flovent (fluticasone) may be used on a daily basis to reduce airway inflammation hyperresponsiveness.

Some healthcare providers endorse a more aggressive approach to treatment under the presumption that it may prevent the onset of classic asthma. This is especially true if coughing fits are severe.

In cases like these, the healthcare provider may prescribe a rescue inhaler, a daily inhaled corticosteroid, and a daily oral drug known as a leukotriene modifier until the chronic cough resolves. If needed, an oral corticosteroid may be added for one to three weeks if the coughing episodes are severe.

Once the symptoms are fully resolved, daily inhaled corticosteroids may be continued to prevent them from returning. A healthcare provider can then monitor your condition and determine how long daily treatment is needed.

A Word From Verywell

Any cough that lasts more than eight weeks in adults or four weeks in children should not be ignored. Speak with your healthcare provider and keep a diary detailing when coughing episodes occur (such as at nighttime or after exercising). The different causes of chronic coughing are treated differently—getting an accurate diagnosis is the first step in getting treatment to relieve your cough.