PURPOSE OF THE STUDY.
Vitamin D deficiency has been hypothesized to be a contributing factor to development of asthma, asthma severity, and asthma exacerbations, but the data are conflicting. The authors aimed to synthesize the epidemiologic literature evaluating the association between vitamin D and asthma incidence, prevalence, severity, and exacerbations.
Observational studies reporting the relationship between asthma measures and 25(OH)D levels in the English-language literature.
A systematic search using PubMed was conducted by using “vitamin D,” “asthma,” and their synonyms. Data were grouped by pediatric versus adult population. Meta-analysis was performed by analyzing the association between serum 25 (OH)D and asthma incidence, prevalence, severity, and exacerbations.
Twenty-three articles were identified. Meta-analysis was limited by small numbers of studies and inconsistent methods for most outcomes. In children, meta-analysis showed a statistically significant relationship between lower vitamin D levels and higher risk of asthma exacerbation, but this was not robust to analysis method. The available data did not support a role for vitamin D in incidence, prevalence, or severity of asthma.
This systematic review and meta-analysis found that in the pediatric population, there is an association between low 25(OH)D and higher risk of asthma exacerbations requiring hospitalization or medical treatment but raised concerns about study methodology, including the role of confounding factors in this association.
This systematic review identified 23 published reports that examined serum vitamin D levels and asthma incidence, prevalence, severity or exacerbation, but found substantial heterogeneity in the literature. The authors call for prospective clinical trials to confirm these observational findings. Because vitamin D is so closely tied to diet, lifestyle, and race/ethnicity, there is a strong possibility of confounding in observational studies, and clinical trials are required to determine whether vitamin D supplementation should be used to prevent asthma exacerbations.
- Copyright © 2015 by the American Academy of Pediatrics