title: Tobacco smoking and intestinal metaplasia: Systematic review and meta-analysis.
abstract: BACKGROUND
  The evaluation of specific risk factors for early endpoints in the gastric carcinogenesis pathway may further contribute to the understanding of gastric cancer aetiology.
  
  
  OBJECTIVE
  To quantify the relation between smoking and intestinal metaplasia through systematic review and meta-analysis.
  
  
  METHODS
  Articles providing data on the association between smoking and intestinal metaplasia were identified in PubMed(®), Scopus(®) and Web of Science™, searched until April 2014, and through backward citation tracking. Summary odds ratio estimates and 95% confidence intervals were computed using the DerSimonian and Laird method. Heterogeneity was quantitatively assessed using the I(2) statistic.
  
  
  RESULTS
  A total of 32 articles were included in this systematic review and 19 provided data for meta-analysis. Smoking was defined as ever vs. never (crude estimates, six studies, summary odds ratio=1.54, 95% confidence interval: 1.12-2.12, I(2)=67.4%; adjusted estimates, seven studies, summary odds ratio=1.26, 95% confidence interval: 0.98-1.61, I(2)=65.0%) and current vs. non-smokers (crude estimates, seven studies, summary odds ratio=1.27, 95% confidence interval: 0.88-1.84, I(2)=73.4%; adjusted estimates, two studies, summary odds ratio 1.49, 95% confidence interval: 0.99-2.25, I(2)=0.0%).
  
  
  CONCLUSIONS
  The weak and non-statistically significant association found through meta-analysis of the available evidence does not confirm smoking as an independent risk factor for intestinal metaplasia.
authors.affiliation: EPIUnit - Institute of Public Health, University of Porto, Porto, Portugal.
authors.forename: Samantha
authors.initials: S
authors.lastname: Morais
authors.affiliation: EPIUnit - Institute of Public Health, University of Porto, Porto, Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rodrigues
authors.affiliation: EPIUnit - Institute of Public Health, University of Porto, Porto, Portugal.
authors.forename: Liliana
authors.initials: L
authors.lastname: Amorim
authors.affiliation: EPIUnit - Institute of Public Health, University of Porto, Porto, Portugal; Department of Clinical Epidemiology, Predictive Medicine and Public Health of the University of Porto Medical School, Porto, Portugal.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Peleteiro
authors.affiliation: EPIUnit - Institute of Public Health, University of Porto, Porto, Portugal; Department of Clinical Epidemiology, Predictive Medicine and Public Health of the University of Porto Medical School, Porto, Portugal. Electronic address: nlunet@med.up.pt.
authors.forename: Nuno
authors.initials: N
authors.lastname: Lunet
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007414:Intestinal Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology*; D008297:Male; D008679:Metaplasia / Q000453:epidemiology / Q000473:pathology; D008875:Middle Aged; D016017:Odds Ratio; D011174:Portugal / Q000453:epidemiology; D011230:Precancerous Conditions / Q000453:epidemiology / Q000473:pathology*; D015995:Prevalence; D011379:Prognosis; D018570:Risk Assessment; D017678:Sex Distribution; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D013274:Stomach Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology; D015996:Survival Rate
keywords: Meta-analysis; Precancerous conditions; Smoking; Stomach neoplasms