title: 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: BACKGROUND
  The 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.
  
  
  METHODS
  This 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.
  
  
  RESULTS
  Asthma 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.
  
  
  CONCLUSIONS
  There 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.
authors.affiliation: Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Shi
authors.initials: S
authors.lastname: Li
authors.forename: Stuart
authors.initials: S
authors.lastname: Batterman
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Wasilevich
authors.forename: Huda
authors.initials: H
authors.lastname: Elasaad
authors.forename: Robert
authors.initials: R
authors.lastname: Wahl
authors.forename: Bhramar
authors.initials: B
authors.lastname: Mukherjee
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000633:toxicity*; D001249:Asthma / Q000453:epidemiology*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D008484:Medicaid; D008824:Michigan / Q000453:epidemiology; D016017:Odds Ratio; D012111:Residence Characteristics; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014504:Urban Health; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions