Keeping blood sugar under control reduces CRC risk in people with diabetes

For individuals with diabetes mellitus (DM), optimal glycaemic control may protect against the risk of developing colonic adenoma and colorectal cancer (CRC), as reported in a population-based cohort study.

A total of 88,468 propensity score-matched patients with DM (mean age 61.5 years, 53.3 percent male) were included in the study. A mean baseline haemoglobin A1c (HbA1c) of <7 percent was used to define optimal glycaemic control.

Researchers analysed outcomes including incident CRC and colonic adenoma by applying competing risk models. They also looked at the combined effect of baseline and postbaseline glycaemic control based on time-weighted mean HbA1c during follow-up.

Over a median follow-up of 7.2 years, 1,229 (1.4 percent) patients received a diagnosis of CRC. Optimal glycaemic control was associated with a 28-percent lower CRC risk (subdistribution hazard ratio [SHR], 0.72, 95 percent confidence interval [CI], 0.65–0.81). This association was observed for left-sided colon (SHR, 0.71, 95 percent CI, 0.59–0.85) and rectum (SHR, 0.71, 95 percent CI, 0.57–0.89) but not right-sided colon (SHR, 0.86, 95 percent CI, 0.67–1.10).

With suboptimal glycaemic control at baseline/postbaseline as a reference, a decreased risk of CRC was observed among patients with optimal glycaemic control at postbaseline (SHR, 0.79), baseline (SHR, 0.71), and both time periods (SHR, 0.61). Results were consistent in an analysis wherein glycaemic control was taken as a time-varying covariate (HR, 0.75).

Meanwhile, patients with suboptimal glycaemic control had progressively greater risk of incident CRC (HbA1c 7.0 percent to <7.5 percent: SHR, 1.34; HbA1c 7.5 percent to <8.0 percent: SHR, 1.30; HbA1c 8.0 percent to <8.5 percent: SHR, 1.44; HbA1c ≥8.5 percent: SHR, 1.58; p<0.001 for trend).

Finally, optimal glycaemic control also showed a protective association with the risk of any, nonadvanced, and advanced colonic adenoma (SHRs, 0.73–0.87).