Can the use of asthma medication protect children from pollution effects?

Published Online: July 14, 2015

Over the past thirty years evidence has accumulated demonstrating that ambient air pollution has adverse effects on the respiratory health of both children with asthma and children without asthma. Inhaled corticosteroids (ICS) are known to improve asthma control and reduce airway hyperresponsiveness in most children with persistent asthma, but it is not known whether they protect children with asthma against the adverse effects of air pollution on lung function. Evaluation of pollution effects in the context of a clinical trial can test whether regular ICS use modifies susceptibility to air pollution.

The Childhood Asthma Management Program (CAMP) is a randomized clinical trial that evaluated the long-term effectiveness and safety of daily inhaled anti-inflammatory medication in children from eight cities in North America who were diagnosed with mild-to-moderate asthma. In an article recently published in The Journal of Allergy & Clinical Immunology (JACI), Ierodiakonou and colleagues examined short- and long-term lung function responses of asthmatic children to gaseous pollutants (ozone, carbon monoxide, nitrogen dioxide, and sulfur dioxide) in 1,003 asthmatic children participating in this trial, and tested longitudinally whether ICS and nedocromil modified the associations of pollution with lung function or airway hyperresponsiveness.

Children five to 12 years of age, all hyperresponsive to methacholine, entered the study and 311, 312, 418 children received budesonide, nedocromil, and placebo, respectively. All subjects were treated and followed for four years with visits at two months and four months intervals thereafter. More than 80% of the children attended all visits during the four years of the trial with on average 14 visits with comprehensive assessment. The authors found that short- and long-term exposure to gaseous pollutants adversely influenced lung function and airway hyperresponsiveness in children with asthma. Their findings also suggest that that use of controller medication may not protect asthmatic children from pollutant effects and may worsen the negative effects of some pollutants.

The authors explain that it is plausible that the children on the ICS had greater exposure to pollution compared to placebo, either because they were more likely to spend more time outside and exercise more due to better control of their asthma, or because they had greater minute ventilation because they were able to breathe more deeply when exercising. The public health interpretation of their findings is that controller medication use should not be assumed to be sufficient as a preventive measure on days with high pollution levels. Policy for pollution control and advice to asthmatic children to avoid outdoor activities on days of high pollution levels remain the most powerful preventive measure.

The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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