Serum vitamin D levels and severe asthma exacerbations in the Childhood Asthma Management Program study

Abstract

Background: Asthma exacerbations, most often caused by respiratory tract infections, are the leading causes of asthma morbidity and comprise a significant proportion of asthma-related costs. Vitamin D status might play a role in preventing asthma exacerbations.

Objectives: We sought to assess the relationship between serum vitamin D levels and subsequent severe asthma exacerbations.

Methods: We measured 25-hydroxyvitamin D levels in sera collected from 1024 children with mild-to-moderate persistent asthma at the time of enrollment in a multicenter clinical trial of children randomized to receive budesonide, nedocromil, or placebo (as-needed beta-agonists): the Childhood Asthma Management Program. Using multivariable modeling, we examined the relationship between baseline vitamin D levels and the odds of any hospitalization or emergency department visit over the 4 years of the trial.

Results: Thirty-five percent of all subjects were vitamin D insufficient, as defined by a level of 30 ng/mL or less 25-hydroxyvitamin D. Mean vitamin D levels were lowest in African American subjects and highest in white subjects. After adjusting for age, sex, body mass index, income, and treatment group, insufficient vitamin D status was associated with a higher odds of any hospitalization or emergency department visit (odds ratio, 1.5; 95% CI, 1.1-1.9; P = .01).

Conclusion: Vitamin D insufficiency is common in this population of North American children with mild-to-moderate persistent asthma and is associated with higher odds of severe exacerbation over a 4-year period.

Figure 1

Vitamin D levels and distributions by (a) study center, (b) season, and (c) race.

Figure 2

Sensitivity analysis of risk of hospitalization or ED visit by vitamin D level. The probabilities of severe exacerbations were plotted for the range of vitamin D levels in the study, and a smoothing function was used to draw a line through the values. Vertical lines represent quartiles of vitamin D levels. The risk of hospitalization start to decline around vitamin D levels of 30 ng/ml.