Vitamin D, Steroids, and Asthma in African American Youth

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.