title: Association between vitamin D deficiency and insufficiency and the risk of childhood asthma: evidence from a meta-analysis.
abstract: 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.
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Man
authors.affiliation: Shandong Traditional Chinese Medicine University China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Shandong Traditional Chinese Medicine University China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pediatrics, People's Hospital of Pingyi Shandong Province, China.
authors.forename: Ju
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zheng
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Ming
authors.initials: M
authors.lastname: Chi
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Yujin
authors.initials: Y
authors.lastname: Chao
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Qiuer
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Chunmei
authors.initials: C
authors.lastname: Song
authors.affiliation: Department of Pediatrics, General Hospital of Jinan Military Area China.
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
keywords: Vitamin D deficiency; childhood asthma; meta-analysis; vitamin D insufficiency