title: Vitamin D deficiency is associated with increased risk of Alzheimer's disease and dementia: evidence from meta-analysis.
abstract: BACKGROUND
  In recent years, the associations between vitamin D status and Alzheimer's disease (AD) and dementia have gained increasing interests. The present meta-analysis was designed to estimate the association between vitamin D deficiency and risk of developing AD and dementia.
  
  
  METHODS
  A literature search conducted until February 2015 identified 10 study populations, which were included in the meta-analysis. Pooled risk ratios (RRs) and 95% confidence interval (CI) were calculated with a random-effect model using Stata software package.
  
  
  RESULTS
  Results of our meta-analysis showed that subjects with deficient vitamin D status (25(OH)D level < 50 nmol/L) were at increased risk of developing AD by 21% compared with those possessing 25(OH)D level > 50 nmol/L. Similar analysis also found a significantly increased dementia risk in vitamin D deficient subjects. There is no evidence for significant heterogeneity among the included studies.
  
  
  CONCLUSIONS
  Available data indicates that lower vitamin D status may be associated with increased risk of developing AD and dementia. More studies are needed to further confirm the associations and to evaluate the beneficial effects of vitamin D supplementation in preventing AD and dementia.
authors.affiliation: Shandong Provincial Research Center for Bioinformatic Engineering and Technique, School of Life Sciences, Shandong University of Technology, Zibo, 255049, P. R. China.
authors.forename: Liang
authors.initials: L
authors.lastname: Shen
authors.affiliation: Shandong Provincial Research Center for Bioinformatic Engineering and Technique, School of Life Sciences, Shandong University of Technology, Zibo, 255049, P. R. China. jhf@sdut.edu.cn.
authors.forename: Hong-Fang
authors.initials: HF
authors.lastname: Ji
mesh_terms: D000544:Alzheimer Disease / Q000097:blood* / Q000150:complications; D003704:Dementia / Q000097:blood* / Q000150:complications; D019587:Dietary Supplements; D006801:Humans; D012307:Risk Factors; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood* / Q000150:complications
chemical_list: D014807:Vitamin D