title: Bayesian model averaging in meta-analysis: vitamin E supplementation and mortality.
abstract: BACKGROUND
  The strength and relevance of a meta-analysis depends on the validity of the statistical methods used. Of special importance is appropriately assessing different sources of variability. Many studies including meta-analyses have evaluated the efficacy and safety of vitamin E and have yielded varying results. Illuminating and resolving these disparities requires addressing study variability and model uncertainty.
  
  
  OBJECTIVE
  To describe Bayesian meta-analysis methods for combining data from clinical trials, using recent studies that analyzed the relationship between vitamin E dose and all-cause mortality.
  
  
  METHODS
  Studies used in a previously published meta-analysis appended by studies identified by a search of MEDLINE from August 2004 to December 2005 using the MeSH terms vitamin e and alpha tocopherol.
  
  
  METHODS
  
  
  
  METHODS
  men and nonpregnant women; use of vitamin E alone or in combination with other vitamins or minerals; random allocation of participants to either vitamin E or a placebo or other control group; intervention and follow-up duration greater than 1 year; 10 or more deaths.
  
  
  METHODS
  Independent data extraction by one author was reviewed and confirmed by a second author. Corresponding authors of the original publications were contacted when questions arose.
  
  
  RESULTS
  Data collection included the number of patients and deaths, percent men, use of other vitamins or minerals, mean age, and length of follow-up. We combined study results using Bayesian hierarchical model averaging. Analyses used Markov chain Monte Carlo computational techniques.
  
  
  CONCLUSIONS
  Vitamin E intake is unlikely to affect mortality regardless of dose. The Bayesian meta-analyses presented here are ideal for incorporating disparate sources of variability, including trial effect and model uncertainty.
authors.affiliation: Department of Biostatistics, University of Texas, MD Anderson Cancer Center, Houston, TX, USA. dberry@mdanderson.org.
authors.forename: Donald
authors.initials: D
authors.lastname: Berry
authors.forename: J Kyle
authors.initials: JK
authors.lastname: Wathen
authors.forename: Margaret
authors.initials: M
authors.lastname: Newell
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage* / Q000009:adverse effects*; D001499:Bayes Theorem; D003627:Data Interpretation, Statistical; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015201:Meta-Analysis as Topic; D009010:Monte Carlo Method; D009026:Mortality; D014810:Vitamin E / Q000008:administration & dosage* / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D014810:Vitamin E