A large cohort study that evaluated Swedish family inpatient and outpatient cancer registries found that those who had diabetes had an increased risk of colorectal cancer (CRC)—the magnitude of risk was similar to having a family history of CRC.

The study had a long timeline and follow-up was conducted between 1964-2015. The 12,614,256 individuals included in the study were born after 1931; 559,375 of them had diabetes and 162,226 had CRC. The authors queried the risk of developing CRC among those who had diabetes and found that:

  • 9-fold greater risk of CRC before 50 years among those diagnosed with diabetes before 50 years (range, 1.6-2.3)
  • 9-fold higher risk of CRC before age 50 years among those diagnosed with diabetes before 50 years who also had a family history of CRC (range, 4.1-12)
  • Lifetime risk of CRC before age 50 years among diabetic patients (0.4%) was similar to those with just a family history of CRC (0.5%). It was double that of the average population (0.2%).

This study confirms the positive association between early-onset diabetes and early-onset CRC and makes a case for earlier CRC screening among young adults with diabetes.

Results from the South Australian Young Onset (SAYO) CRC study identified a similar correlation between personal and family history of diabetes and CRC risk. The study cohort included 50 unrelated young adults up to age 55 years diagnosed with CRC (23-54 years), and 253 controls without CRC (18-54 years). Personal and family history of diabetes was documented in this entire population. The study found:

  • 24% of CRC patients also suffered from type II diabetes compared with 5% of the control group
  • 51% of young adults with CRC had at least one first-degree relative with type II diabetes
  • All patients with a personal history of type II diabetes also had first-degree relatives with type II diabetes
  • 44% of CRC patients under 45 years and 60% of CRC patients 45-54 years had a first-degree relative with type II diabetes

These findings create a very strong case for raising awareness among young adults with diabetes of their increased risk of early-onset CRC, especially if there is a family history of diabetes, so they can initiate CRC screening earlier than the USPSTF recommendation of 50 years.

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