Diabetes Mellitus and the Occurrence of Colorectal Cancer: An Updated Meta-Analysis of Cohort Studies

Background: Recently, it has been found that diabetes patients have a higher incidence of colorectal cancer than the general population, but epidemiological studies examining a potential relationship between the two have produced inconsistent conclusions. Thus, we set out to perform a meta-analysis of cohort studies to evaluate the association between diabetes and colorectal cancer. Materials and Methods: Using diabetes,'' colorectal cancer,'' and associated key words, we performed a systematic review of published cohort studies in multiple databases, including MEDLINE, EMBASE, ISI Web of Knowledge databases, OVID, CNKI, CBMD ISC, WANFANG, and CQVIP. We then applied stringent inclusion and exclusion criteria to identify which studies to include in our analysis. STATA version 12.0 software (StataCorp., College Station, TX) was used to conduct statistical analysis, including consolidated statistics calculations, tests for heterogeneity, and publication bias evaluations. Results: We obtained a total of 532 potential articles. In accordance with our inclusion and exclusion criteria, we selected 29 articles for the meta-analysis. The analysis of extracted information indicated that diabetes is a risk factor for the development of colorectal cancer (relative risk 1.22, 95% confidence interval 1.19-1.26). Subgroup analyses by control populations, regions, gender, follow-up time, and colorectal cancer site also support this finding. Conclusions: The risk of individuals with diabetes to develop colorectal cancer is 1.22 times higher than that of individuals without diabetes. The positive association remains consistent for both men and women and for studies carried out in North America, Europe, and Asia, as well as for different follow-up times.