title: Vitamin D levels in Alzheimer's and Parkinson's diseases: a meta-analysis.
abstract: OBJECTIVE
  Recent accumulating evidence shows that vitamin D deficiency is prevalent in individuals with AD and PD. The purpose of the present study is to perform a meta-analysis on the 25-hydroxyvitamin D (25(OH)D) status in this population of patients.
  
  
  METHODS
  We searched all articles in English published up to March 2012 concerning the 25(OH)D level in AD and PD patients. For AD, six studies covering 319 patients and 573 controls were included in the meta-analysis. For PD, five studies discussing 434 patients and 3451 controls were included.
  
  
  RESULTS
  It was found that AD patients had lower levels of 25(OH)D than healthy controls (summary standardized mean difference [SMD], -1.39; 95% confidence interval [CI], -2.79 to 0.01). Similar results were found for PD patients versus healthy controls (summary SMD, -1.33; 95% CI, -2.44 to -0.21).
  
  
  CONCLUSIONS
  The results indicate that despite the similar mean age between patients and healthy controls in each identified study, both AD and PD patients have lower levels of 25(OH)D than controls.
authors: Shandong Provincial Research Center for Bioinformatic Engineering and Technique, Shandong University of Technology, Zibo, PR China.
authors: Yan
authors: Y
authors: Zhao
authors: Yan
authors: Y
authors: Sun
authors: Hong-Fang
authors: HF
authors: Ji
authors: Liang
authors: L
authors: Shen
mesh_terms: D000544:Alzheimer Disease / Q000097:blood* / Q000503:physiopathology; D006801:Humans; D010300:Parkinson Disease / Q000097:blood* / Q000503:physiopathology; D015995:Prevalence; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000453:epidemiology* / Q000503:physiopathology
chemical_list: D014807:Vitamin D