Open Access Research

Outdoor exposure and vitamin D levels in urban children with asthma

Sonali Bose1*, Patrick N Breysse1, Meredith C McCormack1, Nadia N Hansel1, Robert R Rusher2, Elizabeth Matsui1, Roger Peng1, Jean Curtin-Brosnan1, Gregory B Diette1 and for the Center for Childhood Asthma in the Urban Environment

Author affiliations

1 Johns Hopkins University, Baltimore, MD 21205, USA

2 University of South Carolina, Columbia, SC, USA

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Citation and License

Nutrition Journal 2013, 12:81  doi:10.1186/1475-2891-12-81

Published: 12 June 2013

Abstract

Background

The inner-city pediatric population in the United States has a disproportionate burden of asthma. Recent attention has focused on the immunomodulatory role of vitamin D, which may be protective against disease morbidity. As the primary determinant of vitamin D status in humans is exposure to sunlight, we aimed to determine if 25-OH vitamin D levels in urban preschool children with asthma were low, influenced by time spent outdoors, and associated with asthma morbidity.

Methods

Serum 25-OH vitamin D levels were measured at baseline in a cohort of 121 inner-city children ages 2–6 years with asthma in Baltimore, MD. Participants were followed longitudinally at 3 and 6 months to assess time spent outdoors, asthma symptoms through questionnaires and daily diaries, and allergic markers.

Results

In a predominantly black population of preschool children, the median 25-OH vitamin D level was 28 ng/mL (IQR 21.2-36.9), with 54% of the children below the traditionally sufficient level of 30 ng/mL and 7.4% in the range associated with risk of rickets (< 15 ng/mL). The median time spent outdoors was 3 hours/day (IQR 2–4), and greater time spent outdoors was not associated with higher vitamin D levels. 25-OH vitamin D did not show seasonal variation in our cohort (p = 0.66). Lower 25-OH levels were correlated with higher IgE levels.

Conclusions

Urban African-American preschool children with asthma have high rates of vitamin D insufficiency, and increased outdoor exposure is unlikely to correct these low 25-OH vitamin D levels. Repletion in this population may require dietary supplementation.

Keywords:
Asthma; Vitamin D; Outdoor; Ultraviolet; Exposure