Although large-scale prospective cohort studies have related hyperglycemia to increased risk of cancer overall, studies specifically on colorectal cancer have been generally small. We investigated the association between prediagnostic levels of glycosylated hemoglobin (HbA1c), a marker for average glucose level in blood, and colorectal cancer risk in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition cohort. One thousand and twenty-six incident colorectal cancer cases (561 men and 465 women) and 1,026 matched controls were eligible for the study. Multivariate conditional logistic regression was used to estimate odds ratios (ORS) adjusted for possible confounders. Increasing HbA1c percentages were statistically significantly associated with a mild increase in colorectal cancer risk in the whole population [OR, 1.10; 95% confidence interval (CI), 1.01,1.19 for a 10% increase in HbA1c]. In women, increasing HbA1c percentages were associated with a statistically significant increase in colorectal cancer risk (OR, 1.16; 95% CI, 1.01, 1.32 for a 10% increase in HbA1c) and with a borderline statistically significant increase in rectum cancer (OR, 1.22; 95% CI, 0.99,1.50 for a 10% increase in HbA1c). No significant association with cancer risk was observed in men. The results of the current study suggest a mild implication of hyperglycemia in colorectal cancer, which seems more important in women than in men, and more for cancer of the rectum than of the colon.
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