Asthma has become considerably more prevalent and severe in the U.S. during the last 40 years, particularly affecting youth in urban areas, yet the reasons for this are not clear. There is increasing evidence that vitamin D insufficiency contributes to more severe asthma through increased risk of respiratory infections and decreased sensitivity to glucocorticoids. Indeed, low vitamin D levels are linked with the need for exogenous glucocorticoids and increased asthma severity. Particularly relevant to health disparities, we showed a strong association between vitamin D insufficiency and asthma in urban African American (AA) youth. Importantly, AA youth in ours and other studies had lower vitamin D levels than non-AA participants.
Because AA youth residing in urban Washington, DC have markedly worse asthma than other racial/ethnic groups (e.g. prevalence rate 20% higher than the national rate 15 and emergency department utilization rates up to 5 times the national rates and nearly 10 times the Healthy People 2010 target rate), we will utilize our access to this population at the extreme of asthma disparities to examine the contribution of vitamin D to disparities in the chronic control and acute severity of asthma. The overall goal of this study is to provide critical epidemiological/molecular information that will inform the interpretation of ongoing and impending randomized clinical trials of vitamin D supplementation in asthma, especially with regard to urban AA youth with asthma. We hypothesize that low serum 25-hydroxyvitamin D [25(OH)D] levels are associated with poor chronic asthma control, worse acute asthma severity, and glucocorticoid insensitivity. The knowledge generated by the experiments in this application will be crucial to translation of this inexpensive, easily-accessible, and thereby potentially disparity-reducing prospective therapy for asthma.