title: Type 2 diabetes mellitus and risk of colorectal adenoma: a meta-analysis of observational studies.
abstract: To summarize the relationship between type 2 diabetes mellitus (T2DM) and risk of colorectal adenomas (CRA), we performed a meta-analysis of observational studies.
  
  
  
  To find studies, we searched PubMed, Embase, the Cochrane Library, Web of Science and conference abstracts and related publications for American Society of Clinical Oncology and the European Society of Medical Oncology. Studies that reported relative risks (RRs) or odds ratios (ORs) with 95 % confidence intervals (CIs) for the association between T2DM and risk of CRA were included. The meta-analysis assessed the relationships between T2DM and risk of CRA. Sensitivity analyses were performed in two ways: (1) by omitting each study iteratively and (2) by keeping high-quality studies only. Publication bias was detected by Egger's and Begg's tests and corrected using the trim and fill method.
  
  
  
  This meta-analysis included 17 studies with 28,999 participants and 6798 CRA cases. We found that T2DM was a risk factor for CRA (RR: 1.52; 95 % CI: 1.29-1.80), and also for the advanced adenoma (RR: 1.41; 95 % CI: 1.06-1.87). Patients with existing T2DM (RR: 1.56; 95 % CI: 1.16-2.08) or newly diagnosed T2DM (RR: 1.51; 95 % CI: 1.16-1.97) have a risk of CRA. Similar significant results were found in retrospective studies (RR: 1.57; 95 % CI: 1.30-1.89) and population based cross-sectional studies (RR: 1.46; 95 % CI: 1.21-1.89), but not in prospective studies (RR: 1.27; 95 % CI: 0.77-2.10).
  
  
  
  Our results suggested that T2DM plays a risk role in the risk of developing CRA. Consequently, medical workers should increase the rate of CRA screening for T2DM patients so that they can benefit from behavioural interventions that can help prevent the development of colorectal cancer. Additional, large prospective cohort studies are needed to make a more convincing case for these associations.
authors.affiliation: Medical Service Research Division, Navy Medical Research Institute, Shanghai, China.
authors.forename: Feifei
authors.initials: F
authors.lastname: Yu
authors.affiliation: Department of Health Statistics, Second Military Medical University, No. 800 Xiangyin Road, Shanghai, 200433, China.
authors.forename: Yibin
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Colorectal Surgery, Changhai Hospital, Shanghai, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Health Statistics, Second Military Medical University, No. 800 Xiangyin Road, Shanghai, 200433, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Feng
authors.affiliation: Department of Health Statistics, Second Military Medical University, No. 800 Xiangyin Road, Shanghai, 200433, China.
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Jin
authors.affiliation: Department of Health Statistics, Second Military Medical University, No. 800 Xiangyin Road, Shanghai, 200433, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.affiliation: College of Art & Science, University of San Francisco, San Francisco, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Health Statistics, Second Military Medical University, No. 800 Xiangyin Road, Shanghai, 200433, China. hejia63@yeah.net.
authors.forename: Jia
authors.initials: J
authors.lastname: He
mesh_terms: D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D005260:Female; D006801:Humans; D007328:Insulin / Q000009:adverse effects* / Q000627:therapeutic use; D008297:Male; D064887:Observational Studies as Topic; D012307:Risk Factors
chemical_list: D007328:Insulin
keywords: Colorectal adenoma; Meta-analysis; Type 2 diabetes mellitus