Asthma exacerbation and proximity of residence to major roads: a population-based matched case-control study among the pediatric Medicaid population in Detroit, Michigan

Abstract

BackgroundThe relationship between asthma and traffic-related pollutants has received considerable attention. The use of individual-level exposure measures, such as residence location or proximity to emission sources, may avoid ecological biases.MethodThis study focused on the pediatric Medicaid population in Detroit, MI, a high-risk population for asthma-related events. A population-based matched case-control analysis was used to investigate associations between acute asthma outcomes and proximity of residence to major roads, including freeways. Asthma cases were identified as all children who made at least one asthma claim, including inpatient and emergency department visits, during the three-year study period, 2004-06. Individually matched controls were randomly selected from the rest of the Medicaid population on the basis of non-respiratory related illness. We used conditional logistic regression with distance as both categorical and continuous variables, and examined non-linear relationships with distance using polynomial splines. The conditional logistic regression models were then extended by considering multiple asthma states (based on the frequency of acute asthma outcomes) using polychotomous conditional logistic regression.ResultsAsthma events were associated with proximity to primary roads with an odds ratio of 0.97 (95% CI: 0.94, 0.99) for a 1 km increase in distance using conditional logistic regression, implying that asthma events are less likely as the distance between the residence and a primary road increases. Similar relationships and effect sizes were found using polychotomous conditional logistic regression. Another plausible exposure metric, a reduced form response surface model that represents atmospheric dispersion of pollutants from roads, was not associated under that exposure model.ConclusionsThere is moderately strong evidence of elevated risk of asthma close to major roads based on the results obtained in this population-based matched case-control study.

Neighborhood-Level Factors Related to Asthma in Children Living in Urban Areas

“…In analyzing traffic-related pollution, Cook, deVos, Pereira, Jardin, and Weinstein (2011) and Li et al (2011) used proximity of houses to major roads and estimated traffic counts to analyze asthma. They both used case–control studies to demonstrate increased risk of asthma-related events such as ED visits.…”

Inner City Asthma

“…61–63 Studies have also found that the closer a child lives to a source of outdoor pollutants such as a major highway or bus route, the more problems with asthma symptoms and exacerbations he/she experiences. 64,65 A Rochester, MN study found that after using matching for other asthma risk factors using propensity scores to equalize asthma risk, children living in census tracks with proximity to a major highway or railroad had a higher risk of asthma. 66 Pollutant, interaction with allergens may play a role in the increased sensitization seen in inner-city communities: among 5 to 7 year-olds in New York City, higher levels of polycyclic aromatic hydrocarbons (PAH) were associated with increased levels of cockroach sensitization.…”

Geographic and racial variation in asthma prevalence and emergency department use among Medicaid-enrolled children in 14 southern states

“…Among Medicaid-enrolled children, ED visits and hospitalizations decreased by 41.6% [20]. Proximity to interstate highways has also been associated with higher prevalence of asthma and higher exacerbation rates [21,22]. …”