Association between vitamin D deficiency and insufficiency and the risk of childhood asthma: evidence from a meta-analysis.

OBJECTIVE: Whether vitamin D deficiency and insufficiency are associated with childhood asthma remains unclear. Thus, we conducted a meta-analysis to summarize the evidence from epidemiological studies of vitamin D deficiency and insufficiency and the risk of childhood asthma.
METHODS: Pertinent studies were identified by searching of PubMed and Web of Knowledge. The random effect model was used to combine the results. Meta-regression and subgroups analyses were used to explore potential sources of between-study heterogeneity. Publication bias was estimated using Egger's regression asymmetry test.
RESULTS: Finally, 14 articles with 15 studies including 3424 cases for vitamin D deficiency and 9 articles with 10 studies including 2756 cases for vitamin D insufficiency were included in this meta-analysis. The relative risk (95% confidence interval) of childhood asthma risk for vitamin D deficiency was 1.684 (1.321-2.148), and the associations were significant in America and Europe. Significant association of childhood asthma between vitamin D insufficiency and childhood asthma risk was found overall [1.577 (1.230-2.023)] and the subgroups of America, Europe and Asia. No evidence of significant publication bias between vitamin D deficiency and insufficiency and childhood asthma risk were found.
CONCLUSIONS: Results from this meta-analysis suggested that vitamin D deficiency and insufficiency might increase the risk of childhood asthma.