Inhaled steroids may worsen asthma with air pollution

Asthma is condition characterized by episodes of acute symptomatic flare-ups within the context of of chronic lung inflammation. Steroid medications are problematic as a long-term solution for any chronic inflammatory disorder and can contribute to the degradation of immune tolerance. Research recently published in the Journal of Allergy and Clinical Immunology demonstrates that inhaled corticosteroids may in fact worsen asthma in the presence of CO (carbon monoxide). The authors state:

"Although ambient air pollution has been linked to reduced lung function in healthy children, longitudinal analyses of pollution effects in asthmatic patients are lacking...We sought to investigate pollution effects in a longitudinal asthma study and effect modification by controller medications."

Lung function not protected by inhaled steroid medication

They examined lung function for 1003 children with asthma in response to ozone, carbon monoxide (CO), nitrogen dioxide, and sulfur dioxide concentrations over four years, quantifying the effects of budesonide (Pulmicort) and nedocromil. Indices of lung function included FEV₁ and forced vital capacity (FVC) percent predicted, FEV₁/FVC ratio, and PC₂₀. Their data show that lung function was not protected by the medications during pollutant exposure, and the treatment worsened the effect of CO (carbon monoxide):

"Same-day and 1-week average CO concentrations were negatively associated with postbronchodilator percent predicted FEV₁ (change per interquartile range, −0.33 and −0.41, respectively) and FVC (−0.19 and −0.25, respectively). Longer-term 4-month CO averages were negatively associated with prebronchodilator percent predicted FEV₁ and FVC (−0.36, respectively). Four-month averaged CO and ozone concentrations were negatively associated with FEV₁/FVC ratio. Increased 4-month average nitrogen dioxide concentrations were associated with reduced postbronchodilator FEV₁ and FVC percent predicted. Long-term exposures to sulfur dioxide were associated with reduced PC₂₀ (percent change per interquartile range, −6%). Treatment augmented the negative short-term CO effect on PC₂₀."

Quoted from a news release in Medscape Medical News, coauthor Diane R. Gold, MD, MPH, from the Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, Massachusetts stated:

"This means use of controller medication may not protect asthmatic children from pollutant effects and may actually worsen the negative effects of some pollutants."

Underlying causes of chronic airway inflammation

Investigating and targeting the underlying causes that promote loss of immune tolerance and chronic inflammation including loss of barrier integrity, a dysbiotic microbiome, imbalanced cytokine signaling, food intolerance, deficiencies in key co-factors, and others are fundamental to the functional approach to asthma case management. This deeper analysis by the clinician but produces more gratifying outcomes than immunosuppression by corticosteroids. The authors conclude:

"Air pollution adversely influences lung function and PC₂₀ in asthmatic children. Treatment with controller medications might not protect but rather worsens the effects of CO on PC₂₀."