SCOTTSDALE, ARIZ. – Serum vitamin D level was not significantly associated with atopic dermatitis or disease severity in a single-center study of more than 600 children and adolescents.
However, “we did observe a strong correlation between average serum vitamin D levels and skin type, as well as body mass index,” said Kavita Darji, a medical student at Saint Louis (Mo.) University, who presented the findings in a poster at the annual meeting of the Society for Investigative Dermatology. Those findings challenge the logic of following universal definitions of vitamin D deficiency, especially given the phenotypic heterogeneity of patients in the United States, she added in an interview.
Amy Karon/Frontline Medical News
Ms. Kavita Darji
Serum vitamin D testing is one of most common laboratory assays in this country, but clinicians still debate the risks and benefits of supplementing children and adolescents who test below the Endocrine Society’s threshold for sufficiency (30.0 ng/mL).
To identify factors affecting vitamin D levels, Ms. Darji and her associates reviewed electronic medical charts for patients under age 22 years at Saint Louis University medical centers between 2009 and 2014. The cohort of 655 patients was primarily white (64%) or black (29%), and was nearly equally balanced by gender; their average age was 10 years. The researchers analyzed only the first vitamin D serum measurement for each patient, and defined deficiency as a level under 20 ng/mL, insufficiency as a level between 20 and 29.9 ng/mL, and sufficiency as a level of at least 30 ng/mL.
Serum vitamin D levels were slightly lower among atopic patients, compared with those without atopy, but the difference did not reach statistical significance (about 25 ng/mL vs. about 38 ng/mL; P greater than .05). “We also did not find an association between AD severity and vitamin D level,” Ms. Darji reported. Instead, race and body mass index were the most significant predictors of vitamin D deficiency, probably because these factors directly affect cutaneous photo-induced vitamin D synthesis and the sequestration of fat-soluble vitamins in adipose tissue, she said.
Using the standard definitions, more than 50% of black patients were vitamin D deficient, while less than 30% had sufficient vitamin D levels. In contrast, about 25% of white patients were vitamin D deficient, while nearly 40% had sufficient vitamin D levels (P less than .0001 for proportions of deficiency by race). Furthermore, only about 10% of obese children (those who exceeded the 99th percentile of BMI for age) had sufficient vitamin D levels, compared with more than 40% of underweight children and about 30% of normal-weight children (P less than .00001).
Since vitamin D deficiency was more common among black and obese patients, “maybe they could benefit from a different cut-off value than the standard 30 ng per mL that we used,” Ms. Darji said. “The question is, do they really require these supplements? It may be beneficial to look at the unique characteristics of each patient before supplementing, because the risks of supplementation are considerable in terms of bone health and cardiovascular disease.”
Vitamin D levels did not vary significantly by gender or by month or season measured, Ms. Darji noted. She reported no funding sources and had no disclosures.