Traffic Air Pollution Linked to Repeated Hospital Encounters for Asthma

Air pollution caused by traffic near the home affects asthma severity in children, resulting in repeated hospital encounters, according to a study published this month in Annals of Allergy, Asthma & Immunology, the scientific journal of the American College of Allergy, Asthma, and Immunology.

Ralph J. Delfino, M.D., Ph.D., from the University of California, Irvine, and colleagues, studied records for 2,768 children from two hospitals in northern Orange County, Calif. Beginning with the first hospital encounter, investigators analyzed children's estimated exposures at their home addresses to the traffic-related air pollutants nitrogen oxides (NOx) and carbon monoxide (CO). They estimated the risk of recurrent hospital encounters from exposure to air pollution using recurrent proportional hazards analysis, adjusting for sex, age, health insurance, census-derived poverty, race/ethnicity, residence distance to hospital, and season.

Previous studies have demonstrated that high home or school traffic density is associated with prevalence of diagnosed asthma, but the impact of exposure to traffic on repeated episodes of asthma requiring hospital care is unclear, they report.

"Traffic-related NOx and CO were associated with repeated hospital encounters for asthma in children, suggesting that local traffic-generated air pollution near the home affects asthma symptom severity," the researchers wrote.

Approximately half of the repeated encounters in this study population occurred between ages 1 and 3 years. Based on their significant findings in infants with a primary diagnosis of asthma at their first hospital encounter, the authors suggest that early-life exposures to traffic pollutants may affect asthma severity and development.

Investigators did not find that children of lower socioeconomic status were at increased risk from air pollution exposures. They found evidence that this unexpected result was probably due to follow-up data that was less accurate in this group.

"Prospective environmental data are sparse for high-risk populations who present to the hospital with asthma exacerbations. Additional work with improved assessments of air pollutant exposures and asthma outcomes in such high-risk populations is likely to be fruitful given the present results," Delfino and his colleagues concluded.

For more information, go to www.annallergy.org.

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