Low Vitamin D Tied To Asthma In African American Children

NEW YORK (Reuters Health) - In a group of urban African-American youths, vitamin D deficiency was considerably more prevalent among those with asthma, a new study shows.

Vitamin D deficiency is more common in African Americans than in other races, and African American children are also more likely to have asthma, Dr. Robert J. Freishtat and associates noted in their March 18 online article in the Journal of Pediatrics. However, the role of vitamin D in asthma remains unclear.

Using data from the Asthma Severity Modifying Polymorphisms (AsthMaP) Project, the investigators compared 85 asthmatic children (ages 6 to 20) and 21 healthy controls (ages 6 to 9). Both groups were African-American, with a similar prevalence of obesity and from the same general area of Washington, DC. No one in the study was taking vitamin D supplements.

The authors diagnosed 25-hydroxyvitamin D insufficiency in subjects with levels < 30 ng/mL and deficiency in those with levels < 20 ng/mL.

Median vitamin D level was significantly lower in the asthmatic subjects than in the controls (18.5 vs 40.4 ng/mL, p = 0.002) after adjustment for age, sex, body mass index percentile, and season of sampling.
Similarly, the children with asthma had substantially higher rates of vitamin D insufficiency (86% vs 19%) and deficiency (54% vs 5%).

Results were similar when the researchers confined the analysis to children 9 years old and younger.

Because of the cross-sectional design, the study did not prove causation. For example, the authors say, children with asthma may be out in the sun less often than healthy children, or else low vitamin D contributes to asthma prevalence. They suggest that controlled clinical trials of vitamin D supplementation in young urban African Americans with asthma would help clarify the matter.

"Emerging associations between low vitamin D levels and asthma, obesity, and immunodeficiency necessitate strong consideration for routine vitamin D testing in urban African American youth, particularly those with asthma," Dr. Freishtat, from Children's National Medical Center, Washington, DC, and his associates conclude.