The association of type 2 diabetes and its complications with the risk of colorectal cancer

Abstract

Background: The prevalence of type 2 diabetes (T2D) has increased worldwide during the 21st century. T2D and colorectal cancers (CRC) share risk factors such as obesity. This study aims to estimate the association between T2D and the incidence of primary CRC, and furthermore the association of diabetic complications with the risk of CRC. Methods: We linked exposure data on T2D by severity (presence or absence of complications), overweight and obesity and alcohol related disorders from Care Register for Health Care and CRC cases from the Finnish Cancer Registry to a random sample of 2.5 million Finnish individuals of all ages that were followed from 2000 to 2017. To account for the cumulative burden of exposures, we employed a multi-state model where transition rates to CRC were modeled with Poisson regression, adjusted for age, calendar period, sex, overweight and obesity and alcohol related disorders. Results: The cohort included 171,789 people diagnosed with T2D, with a median age of 67.6 at diagnosis. From the 23 533 CRCs diagnosed in the entire cohort, 2430 were in people with diabetes. Individuals diagnosed with T2D were at a higher risk of CRC (Hazard ratio 1.26, 95 % confidence interval 1.20–1.32). Persons with diabetic complications had a higher risk of CRC than those without complications after 10 years since the initial T2D diagnosis (1.21, 1.02–1.45, p = 0.033). Men with diabetic nephropathy had a significantly higher risk of CRC (1.51, 1.23–1.86) than men with diabetes without nephropathy. Conclusion: Our research shows that people with uncomplicated T2D are at an increased risk of CRC in the first 10 years after T2D diagnosis. The risk of CRC among individuals with complicated T2D remains elevated also in longer term follow-up.