Traffic-related air pollution and asthma hospital readmission in children: a longitudinal cohort study.

OBJECTIVE: To examine the association between exposure to traffic-related air pollution (TRAP) and hospital readmission for asthma or bronchodilator-responsive wheezing. STUDY
DESIGN: A population-based cohort of 758 children aged 1-16 years admitted for asthma or bronchodilator-responsive wheezing was assessed for asthma readmission within 12 months. TRAP exposure was estimated with a land use regression model using the home address at index admission, with TRAP dichotomized at the sample median (0.37 μg/m3). Covariates included allergen-specific IgE, tobacco smoke exposure, and social factors obtained at enrollment. Associations between TRAP exposure and readmission were assessed using logistic regression and Cox proportional hazards models.
RESULTS: The study cohort was 58% African American and 32% white; 19% of the patients were readmitted within 12 months of the original admission. Higher TRAP exposure was associated with a higher readmission rate (21% vs. 16%; P = .05); this association was not significant after adjusting for covariates (aOR, 1.4; 95% CI, 0.9-2.2). Race modified the observed association; white children with high TRAP exposure had 3-fold higher odds of asthma readmission (OR, 3.0; 95% CI, 1.1-8.1), compared with white children with low TRAP exposure. In African American children, TRAP exposure was not associated with increased readmission (OR, 1.1; 95% CI, 0.6-1.8). In children with high TRAP exposure, TRAP exposure was associated with decreased time to readmission in white children (hazard ratio, 3.2; 95% CI, 1.5-6.7) compared with African American children (hazard ratio, 1.0; 95% CI, 0.7-1.4). African American children had a higher readmission rate overall.
CONCLUSION: TRAP exposure is associated with increased odds of hospital readmission in white children, but not in African American children.