title: Cigarette smoking and adenomatous polyps: a meta-analysis.
abstract: OBJECTIVE
  Through the past 2 decades, a consistent association between cigarette smoking and colorectal adenomatous polyps, recognized precursor lesions of colorectal cancer, has been shown. We performed a meta-analysis to provide a quantitative pooled risk estimate of the association, focusing on the different characteristics of the study populations, study designs, and clinical feature of the polyps.
  
  
  METHODS
  We performed a comprehensive literature search of studies linking cigarette smoking and adenomas. We used random effects models to evaluate pooled relative risks and performed dose-response, heterogeneity, publication bias, and sensitivity analyses.
  
  
  RESULTS
  Forty-two independent observational studies were included in the analysis. The pooled risk estimates for current, former, and ever smokers in comparison with never smokers were 2.14 (95% confidence interval [CI], 1.86-2.46), 1.47 (95% CI, 1.29-1.67), and 1.82 (95% CI, 1.65-2.00), respectively. The association was stronger for high-risk adenomas than for low-risk adenomas. Studies in which all controls underwent full colonoscopy showed a higher risk compared with studies in which some or all controls underwent partial colon examination.
  
  
  CONCLUSIONS
  This meta-analysis provides strong evidence of the detrimental effect of cigarette smoking on the development of adenomatous polyps. Smoking is important for both formation and aggressiveness of adenomas.
authors.affiliation: Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan, Italy. edoardo.botteri@ieo.it
authors.forename: Edoardo
authors.initials: E
authors.lastname: Botteri
authors.forename: Simona
authors.initials: S
authors.lastname: Iodice
authors.forename: Sara
authors.initials: S
authors.lastname: Raimondi
authors.forename: Patrick
authors.initials: P
authors.lastname: Maisonneuve
authors.forename: Albert B
authors.initials: AB
authors.lastname: Lowenfels
mesh_terms: D018256:Adenomatous Polyps / Q000453:epidemiology*; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D006801:Humans; D017594:Publication Bias; D012107:Research Design; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012907:Smoking / Q000009:adverse effects*