1. ^aInstitute for Circumpolar Health Studies, University of Alaska Anchorage, 3211 Providence Drive Diplomacy 404, Anchorage, Alaska, USA
2. ^bDepartment of Biostatistics, Vanderbilt University, Nashville, Tennessee, USA
3. ^cDepartment of Biostatistics, University of Washington, Seattle, Washington, USA

Correspondence: ME Gordian, Institute for Circumpolar Health Studies, University of Alaska Anchorage, 3211 Providence Drive Diplomacy 404, Anchorage, AK 99508, USA. Tel.: +1-907-786-6569; Fax: +1-907-786-6576; E-mail: anmeg1@uaa.alaska.edu

Received 18 January 2005; Accepted 8 March 2005; Published online 29 June 2005.

Abstract

This study investigated whether proximity to traffic at residence location is associated with being diagnosed with asthma as a young child. A survey of parents of children (aged 5–7) in kindergarten and first-grade in 13 schools was completed in Anchorage, Alaska, and Geographical Information System (GIS) mapping was used to obtain an exposure measure based on traffic density within 100 m of the cross streets closest to the child's residence. Using the range of observed exposure values, a score of low, medium or high traffic exposure was assigned to each child. After controlling for individual level confounders, relative to the low referent group, relative risks (95% confidence intervals) of 1.40 (0.77, 2.55) and 2.83 (1.23,6.51) were obtained in the medium and high exposure groups, respectively. For the null hypothesis of no difference in risk, a significance level of 0.056 was obtained, which suggests that further investigation would be worthwhile. Children without a family history of asthma were more likely to have an asthma diagnosis if they resided in a high traffic area than children who had one or more parents with asthma. The relative risk for children without a family history of asthma is 2.43 (1.12, 5.28) for medium exposure and 5.43 (2.08, 13.74) for high exposure. For children with a family history of asthma, the relative risk is 0.66 (0.25, 1.74) for medium exposure and 0.67 (0.12, 3.69) for high exposure. The P-value for the overall "exposure-effect" (i.e. both main effects AND interaction terms) is 0.0097.