PURPOSE OF THE STUDY.
Recent data indicate that increased serum concentrations of 25-hydroxyvitamin D are associated with higher percent-predicted forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). These researchers sought to establish the relationship between serum vitamin D levels, pulmonary function, and asthma control.
This was a cross-sectional analysis of Italian children aged 5 to 11 years with asthma (intermittent or persistent) consecutively evaluated at a university hospital–based outpatient clinic in Verona, Italy, in the winter and spring of a single year.
Asthma control was classified according to the Global Initiative for Asthma (GINA) guidelines. Children and parents completed the Childhood Asthma Control Test questionnaire. Pulmonary-function testing was performed according to American Thoracic Society guidelines. A single measurement of each child's serum vitamin D level (25-hydroxy cholecalciferol) was obtained.
Of the 75 asthmatic children, 7 (9.4%) had sufficient vitamin D levels (≥30 ng/mL), 28 (37.3%) had insufficient levels (20–30 ng/mL), and 40 (53.3%) had deficient levels (<20 ng/mL). A statistically significant positive correlation (P = .011) was found between serum levels of vitamin D and asthma-control scores according to the questionnaire. Serum levels of 25-hydroxyvitamin D were associated with percent-predicted FVC (P = .04), but correlation between percent-predicted FEV1 and vitamin D levels was not significant.
Deficient and insufficient vitamin D serum levels were found in most asthmatic children in this study. There was a positive association between vitamin D levels and asthma control, and it was observed that lower vitamin D levels were associated with reduced asthma control. These data suggest that higher vitamin D levels are positively associated with pulmonary function, particularly FVC; however, the correlation is relatively weak.
This study raises the question of whether vitamin D deficiency negatively affects asthma control and pulmonary function. Although the cross-sectional design reveals a correlation between vitamin D insufficiency/deficiency and poor asthma control, it does not prove a causal relationship. As suggested by the authors, interventional studies are warranted to evaluate the effect of vitamin D supplementation in poorly controlled asthmatic patients.
- Copyright © 2011 by the American Academy of Pediatrics