Association of short-term increases in ambient air pollution and timing of initial asthma diagnosis among Medicaid-enrolled children in a metropolitan area.
Wendt-JK; Symanski-E; Stock-TH; Chan-W; Du-XL
Environ Res 2014 May; 131:50-58
OBJECTIVE: We investigated associations of short-term changes in ambient ozone (O3), fine particulate matter (PM2.5) and nitrogen dioxide (NO2) concentrations and the timing of new-onset asthma, using a large, high-risk population in an area with historically high ozone levels. METHODS: The study population included 18,289 incident asthma cases identified among Medicaid-enrolled children in Harris County Texas between 2005-2007, using Medicaid Analytic Extract enrollment and claims files. We used a time-stratified case-crossover design and conditional logistic regression to assess the effect of increased short-term pollutant concentrations on the timing of asthma onset. RESULTS: Each 10 ppb increase in ozone was significantly associated with new-onset asthma during the warm season (May-October), with the strongest association seen when a 6-day cumulative average period was used as the exposure metric (odds ratio [OR]=1.05, 95% confidence interval [CI], 1.02-1.08). Similar results were seen for NO2 and PM2.5 (OR=1.07, 95% CI, 1.03-1.11 and OR=1.12, 95% CI, 1.03-1.22, respectively), and PM2.5 also had significant effects in the cold season (November-April), 5-day cumulative lag (OR=1.11. 95% CI, 1.00-1.22). Significantly increased ORs for O3 and NO2 during the warm season persisted in co-pollutant models including PM2.5. Race and age at diagnosis modified associations between ozone and onset of asthma. CONCLUSION: Our results indicate that among children in this low-income urban population who developed asthma, their initial date of diagnosis was more likely to occur following periods of higher short-term ambient pollutant levels.
Bronchial-asthma; Particulates; Nitrogen-dioxides; Statistical-analysis; Humans; Children; Environmental-pollution; Pollutants; Exposure-levels; Seasonal-factors; Racial-factors; Age-factors;
Author Keywords: Air pollution; Asthma; Child; Incidence; Medicaid
Elaine Symanski, University of Texas School of Public Health, 1200 Herman Pressler Dr., RASW 1028, Houston, TX 77030
University of Texas, Health Science Center, Houston, Texas