Effect of vitamin D and inhaled corticosteroid treatment on lung function in children

Abstract

Rationale: Low vitamin D levels are associated with asthma and decreased airway responsiveness. Treatment with inhaled corticosteroids improves airway responsiveness and asthma control.

Objectives: To assess the effect of vitamin D levels on prebronchodilator FEV(1), bronchodilator response, and responsiveness to methacholine (PC(20), provocative concentration of methacholine producing a 20% decline in FEV(1)) in patients with asthma treated with inhaled corticosteroids.

Methods: We measured 25-hydroxyvitamin D levels in the serum of children with persistent asthma at the time of enrollment in the Childhood Asthma Management Program. We divided subjects into the vitamin D sufficiency (>30 ng/ml), insufficiency (20-30 ng/ml), and deficiency (<20 ng/ml) groups. Covariates included age, treatment, sex, body mass index, race, history of emergency department visits, hospitalizations, and season that vitamin D specimen was drawn. Our main outcome measures were change in prebronchodilator FEV(1), bronchodilator response, and PC(20) from enrollment to 8-12 months.

Measurements and main results: Of the 1,024 subjects, 663 (65%) were vitamin D sufficient, 260 (25%) were insufficient, and 101 (10%) were deficient. Vitamin D-deficient subjects were more likely to be older, African American, and have a higher body mass index compared with the vitamin D-sufficient and insufficient subjects. In the inhaled corticosteroid treatment group, prebronchodilator FEV(1) increased from randomization to 12 months by 140 ml in the vitamin D-deficient group and prebronchodilator FEV(1) increased by 330 ml in the vitamin D insufficiency group and by 290 ml in the vitamin D sufficiency group (P = 0.0072), in adjusted models.

Conclusions: In children with asthma treated with inhaled corticosteroids, vitamin D deficiency is associated with poorer lung function than in children with vitamin D insufficiency or sufficiency.

Figure 1.

Change in (A) prebronchodilator FEV₁ and (B) prebronchodilator FEV₁ percent predicted from randomization to 12 months for vitamin D deficiency (solid line, n = 20), insufficiency (dotted line, n = 69), and sufficiency (dashed line, n = 216) groups, while adjusting for age, sex, race, body mass index, history of emergency department visit, and season that vitamin D level was drawn in patients treated with inhaled corticosteroids. The differences in prebronchodilator FEV₁ and prebronchodilator FEV₁ percent predicted for the vitamin D groups were obtained by multivariate analyses using least-squares means regression. As demonstrated in (A), the change in prebronchodilator FEV₁ for the vitamin D deficiency group (P = 0.0072) is significantly less than for the vitamin D–sufficient group (reference group). The change in prebronchodilator FEV₁ for the vitamin D insufficiency group is not significantly different from that for the vitamin D–sufficient group (P = 0.45). There were no significant differences in baseline prebronchodilator FEV₁ values between the groups at randomization. (B) Similar results are shown for prebronchodilator FEV₁ percent predicted in subjects treated with inhaled corticosteroids. Vitamin D–sufficient subjects experienced an increase of 5.2% in prebronchodilator FEV₁ percent predicted, vitamin D–insufficient subjects experienced an increase of 6.1%, and subjects who were vitamin D deficient experienced an decrease of 1.5% in prebronchodilator FEV₁ percent predicted (P = 0.036 compared with vitamin D–sufficient group).