Ethnic differences in the prevalence of asthma in middle class children

Background: Studies have shown a higher prevalence of asthma among boys compared with girls and in blacks compared with whites, but it has been difficult to separate socioeconomic from racial effects because the blacks in the studied populations were more likely to have low socioeconomic status. Objective: To compare the prevalence of asthma in a socioeconomically homogeneous, middle class, multiethnic population of schoolchildren. Methods: Based on a telephone survey of all families of third-graders in Southfield, Michigan, we ascertained the prevalence of physician-diagnosed asthma and probable undiagnosed asthma. One reason Southfield was chosen for study was because the city comprises an integrated middle class population with only 4% blacks and 7% whites having incomes below federal poverty limits. Results: The lifetime prevalence of asthma was 9.5% (12% for blacks and 6% for whites) and higher in boys (14%) than girls (5%), a pattern that was reflected in period prevalence estimates. The lifetime prevalence of probable undiagnosed asthma was greater in blacks (16.6%) than whites (10.8%), with little sex difference. Adjusting for sex and maternal education, the prevalence of physician-diagnosed asthma and probable asthma were associated independently with black ethnicity. Conclusions: Our study is unique in the similarity of the black and white families' socioeconomic status and residence in the same middle class community. Since access to medical care and macro-environmental conditions were similar across this study population, our results are consistent with the hypothesis that differences in biologic factors between blacks and whites and boys and girls play a role in asthma risk.