title: Effect of statins on serum vitamin D concentrations: a systematic review and meta-analysis.
abstract: BACKGROUND
  We conducted a systematic review and meta-analysis to assess the effects of statin therapy on serum vitamin D concentrations.
  
  
  METHODS
  We searched multiple databases including PubMed, MEDLINE, Web of Science and Google Scholar from inception to May 2016, for studies on the effects of statin treatment on serum vitamin D concentration. Quantitative data synthesis used random-effects models meta-analysis, with sensitivity analysis conducted using the leave-one-out method. Heterogeneity was quantitatively assessed using the I2index. The systematic review's registration number was CRD42016035974.
  
  
  RESULTS
  In all, seven of 644 studies met our selection criteria including three randomized controlled trials (RCT), three observational cohort studies and one case-control study. Across RCTs, treatment with statins was associated a significant increase in serum vitamin D concentrations [weighted mean difference (WMD) 2·71 ng/mL, 95% CI 0·19-5·24, I262·1%). Across studies of non-RCT design, statins treatment was associated with a decrease in vitamin D concentrations (WMD -0·70 ng/mL, 95% CI -1·20 to -0·20, I256·3%). These findings were robust in sensitivity analyses.
  
  
  CONCLUSIONS
  This meta-analysis was inconclusive on the effects of statins on vitamin D, with conflicting directions of the effects from interventional and observational studies. The suggested favourable effects from RCTs need to be confirmed in larger studies with extended follow-up in order to determine the possible health benefits.
authors.affiliation: Key State Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Chaoyang, Beijing, China.|Institute of Genetics and Developmental Biology, International College, University of Chinese Academy of Science (IC-UCAS), Chaoyang, China.
authors.forename: Mohsen
authors.initials: M
authors.lastname: Mazidi
authors.affiliation: Biochemistry and Nutrition Research Center, School of Medicine, Mashhad University of Medical Science, Mashhad, Iran.
authors.forename: Peyman
authors.initials: P
authors.lastname: Rezaie
authors.affiliation: College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada.
authors.forename: Hassan
authors.initials: H
authors.lastname: Vatanparast
authors.affiliation: Non-Communicable Disease Research Unit, South African Medical Research Council, University of Cape Town, Cape Town, South Africa.
authors.forename: Andre Pascal
authors.initials: AP
authors.lastname: Kengne
mesh_terms: D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D014807:Vitamin D / Q000097:blood*
chemical_list: D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D014807:Vitamin D
keywords: Meta-analysis; statins; vitamin D