Racial differences in physiologic parameters related to asthma among middle-class children

Background: Asthma morbidity and mortality are higher in the United States for African-American (AA) children when compared to European-American (EA) Children. Study objectives: To explore racial differences in physiologic factors associated with pediatric asthma severity. Design: Cross-sectional. Methods: We analyzed data from two groups of children in suburban Detroit, one of which contains non-urban, middle-class AA children, a group not usually included in childhood asthma studies. All children were 6 to 8 years of age. Clinical evaluations included medical history, physical examination, skin testing, spirometry, and methacholine challenge. Results: The study population (n = 560) was 14% African American, 51% of the participants were male, and the mean age was 6.8 ± 0.4 years. Socioeconomic status (parental education) was similar overall by race, although some strata-specific differences were observed. The prevalence of physician-diagnosed asthma was 10% for both AA and EA groups. AA children were more reactive to methacholine than EA children (42% vs 22%, respectively; p = 0.001), and had significantly higher total IgE than EA children (geometric mean, 60.6 vs 27.5 IU/mL; p = 0.001). Serum IgE was related to methacholine reactivity in EA children (p = 0.001), but not AA children (p = 0.73). These differences remained after adjustment for gender, age, parental education, parental smoking, and maternal smoking during pregnancy. Conclusions: Our data support previous reports of racial differences in lung volume, airway responsiveness, and serum IgE concentrations. We found a racial difference in the relationship between total serum IgE and airway responsiveness that is unreported elsewhere. Overall, our results suggest that AA children may be predisposed to asthma.