Prevalence of Asthma in School Children on the Arizona-Sonora Border

Background Mexican-born children living in the United States have a lower prevalence of asthma than other US children. Although children of Mexican descent near the Arizona (AZ)-Sonora border are genetically similar, differences in environmental exposures might result in differences in asthma prevalence across this region. Objective The objective of this study was to determine if the prevalence of asthma and wheeze in these children varies across the AZ-Sonora border. Methods The International Study of Asthma and Allergy in Children written and video questionnaires were administered to 1753 adolescents from 5 middle schools: Tucson (school A), Nogales, AZ (schools B, C), and Nogales, Sonora, Mexico (schools D, E). The prevalence of asthma and symptoms was compared, with analyses in the AZ schools limited to self-identified Mexican American students. Results Compared with the Sonoran reference school E, the adjusted odds ratio (OR) for asthma was significantly higher in US schools A (OR 4.89, 95% confidence interval [CI] 2.72-8.80), B (OR 3.47, 95% CI 1.88-6.42), and C (OR 4.12, 95% CI 1.78-9.60). The adjusted OR for wheeze in the past year was significantly higher in schools A (OR 2.19, 95% CI 1.20-4.01) and B (OR 2.67, 95% CI 1.42-5.01) on the written questionnaire and significantly higher in A (OR 2.13, 95% CI 1.22-3.75), B (OR 1.95, 95% CI 1.07-3.53), and Sonoran school D (OR 2.34, 95% CI 1.28-4.30) on the video questionnaire compared with school E. Conclusions Asthma and wheeze prevalence differed significantly between schools and was higher in the United States. Environmental factors that may account for these differences could provide insight into mechanisms of protection from asthma.