Abstract
BackgroundThe 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.MethodsSerum 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.ResultsIn 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.ConclusionsUrban 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.
Highlights
Asthma morbidity is strikingly high among inner-city children in the United States, especially among AfricanAmericans [1,2]
The findings from this study suggest that, UV light is necessary for dermal vitamin D production, black urban children with asthma appear to be unresponsive to what little daily sunlight they do receive, as higher daily levels of outdoor exposure were not linked to higher 25-OH D
Our study showed that vitamin D insufficiency is common in highly affected African-American preschool-aged children with asthma, and that increases within the range of time typically spent outdoors by urban children would not be an effective strategy for repletion
Summary
Asthma morbidity is strikingly high among inner-city children in the United States, especially among AfricanAmericans [1,2]. While the reasons for this disparity are not entirely clear, several risk factors, including an urban environment enriched with air pollutants and unique allergens, lower socio-economic status, and poor diet, may predispose such children to more severe disease [2]. Of these factors, serum 25 hydroxy (OH) vitamin D levels are disproportionately low in such populations [3,4,5] and may help to explain higher rates of asthma darker skin and a diet inadequate to compensate for deficiencies in production. 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
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