Proximity to major roadways and asthma symptoms in the School Inner-City Asthma Study

Background: Traffic proximity has been associated with adverse respiratory health outcomes. Less is known about the combined impact of residential and school exposures on pediatric asthma. Objective: We sought to use spatial analysis methodology to analyze residential and school proximity to major roadways and pediatric asthma morbidity. Methods: The School Inner-City Asthma Study (n = 350) recruited school-aged children with asthma. Each participant's school and home addresses were geocoded, and distances from major roadways were measured to calculate a composite measure accounting for both home and school traffic exposure. Generalized estimating equation models were clustered by subject and adjusted for age, race/ethnicity, sex, income, environmental tobacco smoke, controller medication, upper respiratory tract infections, and seasonality. Results: The majority of participants (62%) attended schools within 100 m from major roadways, and 40% also resided within 100 m of major roadways. In multivariate analyses major roadway proximity was independently associated with increased asthma symptom days. At greater than the threshold of 100 m, children had 29% less odds of a symptom day over the past 2 weeks for each 100-m increase in distance from a major roadway (odds ratio, 0.71; 95% CI, 0.58-0.87; P < .01). Children farther from a major roadway also had significantly less reported health care use (odds ratio, 0.63; 95% CI, 0.47-0.85; P <.01) and were significantly less likely to have poor asthma control (odds ratio, 0.80; 95% CI, 0.69-0.94; P <.01). There was not a meaningful association between distance to a major roadway and lung function outcomes. Conclusions: Proximity to a major roadway, a composite measure of home and school exposure but primarily driven by home exposure, was associated with greater asthma morbidity. More studies are needed to evaluate the independent effect of school distance to a roadway on asthma morbidity.