Review: Diabetes is associated with a significantly increased risk of colorectal cancer

Clinical question

Is diabetes a risk factor for colorectal cancer?

The Evidence

The reviewers found 24 studies in Medline and EMBASE.  They combined the data from these studies to estimate out the relative risk of colorectal cancer in people with diabetes compared with people without diabetes.

They found that people with diabetes had a significantly higher risk of colorectal cancer.  The relative risk was 1.28 (95% confidence interval 1.19 – 1.39).

Appraisal hints

Users of this evidence are advised to consider:

  • This evidence does not prove a causal link between the diabetes and colorectal cancer.  Perhaps some other factor is causing both.
  • Whether the reviewers did enough to find all of the relevant data in this area
  • The quality assessment applied to the studies
  • The details of the subgroup analyses performed (e.g. by type or duration of diabetes, age, gender, etc.)
  • Whether the studies were sufficiently similar to warrant their combination in a meta-analysis.


Luo W, Cao Y et al. Diabetes mellitus and the incidence and mortality of colorectal cancer: A meta-analysis of twenty four cohort studies.
Colorectal Dis. 2011 Nov 5. doi: 10.1111/j.1463-1318.2011.02875.x. [Epub ahead of print]