Impact of asthma control on susceptibility to ambient air pollution among African American teens with asthma

RATIONALE: Despite overall improvements in air quality, exposure to ambient air pollution continues to cause asthma exacerbations. Having poorly controlled asthma increases risk of future asthma exacerbations; African-American teens are at high risk of having poorly controlled asthma. We hypothesized that having poorly controlled asthma increases susceptibility to ambient air pollution among African-American teens.

METHODS: This was a prospective observational study of 23 African-American teens with persistent asthma requiring controller therapies ages 12-17 followed at a subspecialty clinic. Participants completed questionnaires, performed spirometry, and underwent a history and physical exam at each of the six study visits over an 8-week period. At the baseline visit, study physicians classified participants’ asthma as “well-controlled” or “not-well controlled” in accordance with NHLBI guidelines. A linear mixed effects model was used to evaluate the relationship of each outcome to ambient ozone concentrations at each visit and in prior days.

RESULTS: At the baseline visit, 14/23 participants had well-controlled asthma. After controlling for particulate matter exposure, an increase in ozone levels was associated with decrements of 2.7% in FVC (p=0.02) and of 2.5% in FEV₁ (p=0.07) per interquartile range (0.017 ppm) on the day of exam. Likewise, an increase in ozone levels was associated with a 0.93 increase in the total Asthma Control Questionnaire score (p<0.001). There was no effect modification by baseline level of asthma control.

CONCLUSIONS: Among African-American teens exposed to ozone levels below the National Ambient Air Quality Standard, having “well-controlled” asthma was not sufficient to protect against the pulmonary health effects of ambient air pollution.