title: Body mass index increases risk for colorectal adenomas based on meta-analysis.
abstract: OBJECTIVE
  There have been inconsistent results published about the relationship between excess body weight, expressed as increased body mass index (BMI), and risk of colorectal adenoma (CRA). We conducted a meta-analysis to explore this relationship. We focused on whether the relationship varied based on the sex of the study subjects, study design, features of the polyps, or potential confounders, including alcohol use, nonsteroidal anti-inflammatory drug use, smoking, and exercise.
  
  
  METHODS
  We identified studies by performing a literature search of Medline, EMBASE, and ISI Web of Science through July 31, 2011, and by searching the reference lists of pertinent articles. We analyzed 36 independent studies, which included 29,860 incident cases of CRA. Summary relative risks with their 95% confidence intervals (CIs) were calculated with a random-effects model. Between-study heterogeneity was assessed using Cochran's Q statistic and I(2) analyses.
  
  
  RESULTS
  Overall, a 5-unit increase in BMI (calculated as kg/m(2)) increased the risk for CRA (summary relative risk = 1.19; 95% CI: 1.13-1.26), although there was a high level of heterogeneity among studies (P(heterogeneity) < .001; I(2) = 76.8%). Subgroup analyses revealed that the increased risk of CRA in obese individuals was independent of race, geographic location, study design, sex, adenoma progression, and confounders. The association between increased BMI and risk for CRA was stronger for colon than rectal adenoma.
  
  
  CONCLUSIONS
  Based on a meta-analysis, increased BMI increases the risk for colon but not rectal adenoma. Unlike colorectal cancer, there is no sex difference in the relationship between increased BMI and risk of CRA.
authors.affiliation: Department of Gastroenterology, Changhai Hospital of Second Military Medical University, Shanghai, China.
authors.forename: Qiwen
authors.initials: Q
authors.lastname: Ben
authors.forename: Wei
authors.initials: W
authors.lastname: An
authors.forename: Ying
authors.initials: Y
authors.lastname: Jiang
authors.forename: Xianbao
authors.initials: X
authors.lastname: Zhan
authors.forename: Yiqi
authors.initials: Y
authors.lastname: Du
authors.forename: Quan Cai
authors.initials: QC
authors.lastname: Cai
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.forename: Zhaoshen
authors.initials: Z
authors.lastname: Li
mesh_terms: D000236:Adenoma / Q000208:ethnology / Q000209:etiology* / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015179:Colorectal Neoplasms / Q000208:ethnology / Q000209:etiology* / Q000473:pathology; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000175:diagnosis / Q000208:ethnology; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors