Patients with very mild or well-controlled asthma can significantly improve day-to-day lung function if regularly treated with low dose inhaled corticosteroids (ICS), according to a new study published in Primary Care Respiratory Journal. The study was conducted by researchers at the Woolcock Institute of Medical Research in Sydney, Australia.

Asthma is a respiratory condition in which the airway constricts, become inflamed, and is lined with excessive amounts of mucous. Inhaled corticosteroids that suppress inflammation and reduce the swelling of the airway lining are commonly prescribed to help prevent asthma. The Australian researchers conducted a study over an 11 month period in order to compare the effects of ICS and placebo on asthma control in mild asthmatics.

The results of the randomized, double-blind placebo study showed significant and clinically important treatment benefits of ICS on several markers. These include lung function, airway hyperresponsiveness and exhaled nitric oxide – all predictors of exacerbation (asthma attack) risk and other adverse outcomes. Currently asthma treatment is based on controlling symptoms, but it does not recommend ICS treatment if patients only have symptoms two days a week or less. The authors suggest that the results of this study lead to questions about the appropriate treatment and prevention strategies.

Further, results indicated that contrary to common beliefs about mild asthma, there is no “ceiling” effect for lung function. For patients whose lung function is over 90% of predicted normal value, there may be room for improvement if treated.

“While we’re not advocating that every patient with mild asthma should be on preventer medication, the study shows that when we are discussing the risks and benefits of treatment with these patients, we should talk about their risk of future exacerbations as well as whether they will notice any difference in their current symptoms,” writes research leader Assoc. Prof. Helen Reddel.

Study participants who received placebo were almost 3 times as more likely to experience a mild exacerbation.

Reddel comments that: “In recent years the emphasis in asthma treatment has been on how well a patient’s symptoms are controlled.” In this study, the patients had asthma that was so mild “with symptoms once a week or less, that they themselves didn’t see any benefit in regular preventer treatment.”

“However for those participants receiving ICS during the study, their lung function was better, they had less airway inflammation and less airway twitchiness. All of these things are predictors of reduction in risk of future adverse outcomes.” Although the sample size was small, the authors were able to get measurements of airway twitchiness, airway inflammation and daily spirometry. These data are useful in determining future risk and are often not easily obtainable in larger groups.

Does continuous use of inhaled corticosteroids improve outcomes in mild asthma? A double-blind randomised controlled trial
Helen K Reddel, Elena G Belousova, Guy B Marks, Christine R Jenkins
Primary Care Respiratory Journal. (2008). 17(1):39-45.
doi: 10.3132/pcrj.2008.00014
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Written by: Peter M Crosta