title: Relation of Vitamin E and Selenium Exposure to Prostate Cancer Risk by Smoking Status: A Review and Meta-Analysis.
abstract: BACKGROUND
  Epidemiological studies of selenium and vitamin E, two antioxidants hypothesized to reduce prostate cancer risk, have shown no discernible benefit. It has been proposed, however, that tobacco smoking may modify the effect of these nutrients.
  
  
  METHODS
  We performed a meta-analysis of studies evaluating the relation of vitamin E and selenium exposure to prostate cancer risk in never smokers vs. ever smokers and, when feasible, former and current smokers. Overall and stratum-specific meta-risk ratios (meta-RRs) and 95% confidence intervals (CIs) were calculated using random-effects models.
  
  
  RESULTS
  A total of 21 studies have met the inclusion criteria. Meta-RR (95% CI) estimates of prostate cancer associated with vitamin E use were 1.03 (0.95-1.11) in never smokers and 0.98 (0.90-1.07) in ever-smokers. For selenium, meta-RRs were 1.09 (0.78-1.52 and 0.76 (0.60-0.96) for never and ever-smokers, respectively; however, results for current smokers were weaker than those for former smokers. Sub-analyses according to different exposure assessment methods and outcome definitions produced similar results across strata.
  
  
  CONCLUSIONS
  The association between vitamin E and prostate cancer is not modified by smoking. Selenium exposure is associated with lower prostate cancer risk among ever-smokers; however, the lack of an association for current smokers indicates that this finding needs to be interpreted with caution.
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, U.S.A. Department of Internal Medicine, University of Maryland School of Medicine, Baltimore, MD, U.S.A.
authors.forename: Yeunjung
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, U.S.A. Department of Epidemiology, Gillings School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, U.S.A. jingkai@live.unc.edu.
authors.forename: Jingkai
authors.initials: J
authors.lastname: Wei
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, U.S.A.
authors.forename: Jessica
authors.initials: J
authors.lastname: Citronberg
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, U.S.A. Winship Cancer Institute, Emory University, Atlanta, GA, U.S.A.
authors.forename: Terryl
authors.initials: T
authors.lastname: Hartman
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, U.S.A. Winship Cancer Institute, Emory University, Atlanta, GA, U.S.A.
authors.forename: Veronika
authors.initials: V
authors.lastname: Fedirko
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, U.S.A. Winship Cancer Institute, Emory University, Atlanta, GA, U.S.A.
authors.forename: Michael
authors.initials: M
authors.lastname: Goodman
mesh_terms: D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D012044:Regression Analysis; D012307:Risk Factors; D012643:Selenium / Q000494:pharmacology*; D012907:Smoking / Q000009:adverse effects*; D014810:Vitamin E / Q000494:pharmacology*
chemical_list: D014810:Vitamin E; D012643:Selenium
keywords: Selenium exposure; Vitamin E; prostate cancer risk; smoking status