title: Smoking-associated risks of conventional adenomas and serrated polyps in the colorectum.
abstract: OBJECTIVE
  Prior studies suggest cigarette smoking is associated with 1.5- to twofold increased risk of colorectal adenomas and possibly a higher risk of serrated polyps. Further clarification of risk differences between adenomas and serrated polyps is needed with regard to co-occurrence and polyp location.
  
  
  METHODS
  We conducted a combined analysis of conventional adenoma and serrated polyp occurrence using individual-level data from 2,915 patients participating in three colonoscopy-based clinical trials. All participants had ≥1 adenomas removed at baseline and were followed for up to 4 years. Smoking habits and other lifestyle factors were collected at baseline using questionnaires. We used generalized linear regression to estimate risk ratios and 95 % confidence intervals.
  
  
  RESULTS
  Smokers were at slightly increased risk of adenomas compared to never smokers [current: RR 1.29 (95 % CI 1.11-1.49) and former: RR 1.18 (1.05-1.32)]. Smoking was associated with greater risk of serrated polyps [current: RR 2.01 (1.66-2.44); former: RR 1.42 (1.20-1.68)], particularly in the left colorectum. Associations between current smoking and occurrence of serrated polyps only [RR 2.33 (1.76-3.07)] and both adenomas and serrated polyps [RR 2.27 (1.68-3.06)] were more pronounced than for adenomas only [RR 1.31 (1.08-1.58)]. Results were similar for other smoking variables and did not differ by gender or for advanced adenomas.
  
  
  CONCLUSIONS
  Cigarette smoking has only a weak association with adenomas, but is associated with a significantly increased risk of serrated polyps, particularly in the left colorectum. Since a minority of left-sided serrated polyps is thought to have malignant potential, the role of smoking in initiation phases of carcinogenesis is uncertain.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA, janefigu@usc.edu.
authors.forename: Jane C
authors.initials: JC
authors.lastname: Figueiredo
authors.forename: Seth D
authors.initials: SD
authors.lastname: Crockett
authors.forename: Dale C
authors.initials: DC
authors.lastname: Snover
authors.forename: Carolyn B
authors.initials: CB
authors.lastname: Morris
authors.forename: Gail
authors.initials: G
authors.lastname: McKeown-Eyssen
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sandler
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Ahnen
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Robertson
authors.forename: Carol A
authors.initials: CA
authors.lastname: Burke
authors.forename: Robert S
authors.initials: RS
authors.lastname: Bresalier
authors.forename: James M
authors.initials: JM
authors.lastname: Church
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Church
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
mesh_terms: D000236:Adenoma / Q000453:epidemiology* / Q000209:etiology; D000368:Aged; D003111:Colonic Polyps / Q000453:epidemiology* / Q000209:etiology; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006801:Humans; D008019:Life Style; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D016032:Randomized Controlled Trials as Topic; D012306:Risk; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D011795:Surveys and Questionnaires