Diabetes mellitus and the risk of cancer - Results from a large-scale population-based cohort study in Japan

Background: An association between diabetes mellitus (DM) and cancer has long been speculated, but no conclusive evidence has been obtained. Methods: We prospectively examined the association between a history of DM and subsequent risk of cancer in the Japan Public Health Center-Based Prospective Study. A total of 97 771 general Japanese persons (46 548 men and 51 223 women) aged 40 to 69 years who responded to the baseline questionnaire, from January 1990 to December 1994, were followed up for cancer incidence through December 31, 2003. At baseline, 6.7% of men and 3.1% of women had a history of DM. Results: A total of 6462 cases of newly diagnosed cancer were identified. In men, a 27% increase in the risk of total cancer incidence was observed in those with a history of DM (n=3907 [366 with DM]; hazard ratio [HR], 1.27; 95% confidence interval [CI], 1.14-1.42). The HR was especially high for those with cancer of the liver (n=312 [52 with DM]; HR, 2.24; 95% CI, 1.64- 3.04), pancreas n=118 [16 with DM]; HR, 1.85; 95% CI, 1.07-3.20), and kidney (n=99 [13 with DM]; HR, 1.92; 95% CI, 1.06-3.46). We also observed a moderately increased risk of colon cancer (n=491 [46 with DM]; HR, 1.36; 95% CI, 1.00-1.85) and of stomach cancer with borderline significance (n=977 [87 with DM]; HR, 1.23; 95% CI, 0.98-1.54). In women, a borderline significant increase in risk was observed for the incidence of total cancer (n=2555 [104 with DM]; HR, 1.21; 95% CI, 0.99-1.47), while statistical significance was observed for the incidence of stomach cancer (n=362 [20 with DM]; HR, 1.61; 95% CI, 1.02-2.54) and liver cancer (n=120 [10 with DM]; HR, 1.94; 95% CI, 1.00-3.73) and borderline significance was observed for the incidence of ovarian cancer n=74 [5 with DM]; HR, 2.42; 95% CI, 0.96-6.09). Conclusion: Patients with DM drawn from the general Japanese population may be at increased risk of total cancer and of cancer in specific sites.