Relationship between type-2 diabetes and use of metformin with risk of colorectal adenoma in an American population receiving colonoscopy

The aim of this study is to explore the relationship between type-2 diabetes, its treatments (Use of metformin) and the development of colorectal adenoma. Colonoscopy reports from a total of 66 endoscopists in one big hospital in midwest during 2008–2009 were reviewed. Colonoscopy findings including quality of preparation, polyp size, location, morphology, pathology and history of diabetes and metformin treatment were retrieved. Of the 7382 colonoscopy reports were reviewed, 3465 average risk patients were included in our final analysis. The pathologically proven Adenoma detection rate (ADR) in total population was 24.6 % (30.2% in Men and 19.2% in Women). Old age and male sex were significantly associated with increasing risk of colorectal adenoma. Type-2 diabetes was associated increased risk of colorectal adenoma (OD 1.35, 95% confidence interval 1.08–1.70, p = 0.009). A total of 426 subjects (12.29%) had diabetes and 405 of these subjects (11.7%) had type-2 diabetes. Within diabetic patient group, people who were taking metformin have significantly lower risk of colorectal adenoma (OD 0.55, 95% confidence interval 0.34–0.87, p = 0.011). Diabetic subjects have increased risk of developing colorectal adenoma. Our study also supports the beneficial effect of metformin in development of colorectal adenoma.