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

To examine the association between exposure to traffic-related air pollution (TRAP) and hospital readmission for asthma or bronchodilator-responsive wheezing.

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.

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.

TRAP exposure is associated with increased odds of hospital readmission in white children, but not in African American children.