Risk of Colorectal Cancer in Type 2 Diabetic Patients: A Population-based Cohort Study

Objective: Most of the existing findings on the association between diabetes mellitus and colorectal cancer were generated from studies in Western societies. However, significant differences in cancer incidence and cancer-prone lifestyles are apparent between Asian and Western countries. This study aims to estimate the risks of colorectal cancer in the diabetic population in Taiwan by conducting a large-scale, controlled cohort study. Methods: From Taiwan's Longitudinal Health Insurance Database 2005 (LHID2005), a total of 37 001 diabetic patients were identified. We also obtained data for four controls per patient, matched for sex, age and year of first entry into the LHID2005. All patients were followed up from the date of entry into the LHID2005 until they developed colorectal cancer or to the end of 2006, whichever was earlier. We used Cox's regression models to assess the risk of developing colorectal cancer, with adjustment for sex, age, comorbid disorders, and socioeconomic characteristics. Results: We identified 37 001 diabetic patients and 148 004 controls. The adjusted hazard ratio for colorectal cancer in diabetes mellitus patients was 2.1 (95% confidence interval, 1.82-2.42) compared with controls. The risk was significant to both men and women. The adjusted hazard ratios for colorectal cancer were 2.03 (95% confidence interval, 1.68-2.47) in male diabetes mellitus patients and 2.17 (95% confidence interval, 1.77-2.67) in female diabetes mellitus patients. Conclusions: Our findings based on a large population-based cohort study provide evidence that diabetes mellitus may increase the risk of colorectal cancer in Asians.