Type 2 diabetes mellitus and the risk of colorectal cancer.
OBJECTIVE
Type 2 diabetes mellitus might increase the risk of colorectal cancer on the basis of chronic hyperinsulinemia and hyperglycemia. However, epidemiologic evidence for this association is inconclusive. We conducted a population-based study to clarify this association.


METHODS
We conducted a case-control study in the United Kingdom General Practice Research Database. Cases included all patients with incident colorectal cancer diagnoses (n = 10,447). Up to 10 control subjects were selected for each case, matching on year of birth, enrollment date, and duration of database follow-up. The exposure of interest was type 2 diabetes mellitus. Odds ratios (ORs) were calculated by using conditional logistic regression.


RESULTS
A prior diagnosis of type 2 diabetes mellitus was associated with a modestly increased risk of colorectal cancer (OR, 1.42; 95% confidence interval [CI], 1.25-1.62). The association between type 2 diabetes mellitus and colorectal cancer was observed in both men (OR, 1.36; 95% CI, 1.16-1.61) and women (OR, 1.38; 95% CI, 1.14-1.67). The risk increase was observed in both colon (OR, 1.45; 95% CI, 1.25-1.70) and rectal (OR, 1.34; 95% CI, 1.08-1.68) cancers.


CONCLUSIONS
Type 2 diabetes mellitus is associated with an increased risk of colorectal cancer. The risk increase is present in both sexes, as well as in both colonic and rectal cancers.
Yang
Yu-Xiao
YX
Division of Gastroenterology, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. yang.xiao@uphs.upenn.edu
Hennessy
Sean
S
Lewis
James D
JD
D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000175:diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D016017:Odds Ratio; D011159:Population Surveillance; D012189:Retrospective Studies; D012307:Risk Factors; D017678:Sex Distribution; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects; D006113:United Kingdom / Q000453:epidemiology