Age- and sex-specific risks of colorectal cancers in diabetic patients.

Diabetes has been reported to increase the risk of colorectal neoplasm in most but not all studies. However, the data on age- and sex-specific incidence rates and relative risks associated with diabetes are limited. We carried out this population-based cohort study to investigate the overall sex- and age-specific risks of colorectal cancer in association with diabetes. Diabetic patients (n = 615,532) and age- and sex-matched control individuals (n = 614,871), selected from the claim datasets, were followed up from 2000 to 2006. The rates of admission due to colon and rectum cancers were estimated using the person-years approach, and the age- and sex-specific hazard ratio (HR) for both the malignancies were determined using the Cox regression model. The overall incidence rate of colon cancer was 9.94 per 10,000 patient-years for the diabetic patients, as opposed to 7.84 per 10,000 patient-years for the control-group patients. The corresponding observation for rectal cancer was 7.16 and 6.28 per 10,000 patient-years. Diabetic patients aged ≥ 45 years had significantly high HRs for developing colon cancer (1.20-1.45-fold). We also noted a significantly high HR of rectal cancer in diabetic men (1.18-fold) aged ≥ 45 years, but not in diabetic women. In conclusion, diabetes may significantly increase the risk of colorectal cancer, especially in patients aged 45-64 years. Diabetologists should keep this relationship in mind while treating middle-aged diabetic men and should also advise these patients to undergo regular screening tests for colorectal cancer.