History of diabetes mellitus and the risk of prostate cancer: the Ohsaki Cohort Study

Objective The association between diabetes mellitus and the risk of prostate cancer has been tested in previous prospective cohort studies in western populations. However, no evidence from cohort studies is available for Asian populations, whose lifestyle is very different from that of westerners. Methods The authors examined the relationship between diabetes mellitus and the risk of prostate cancer in the Ohsaki cohort followed from 1995 to 2003, in which 230 new cases of prostate cancer were identified among 22,458 Japanese men. Baseline information including diabetes mellitus status was collected using a self-administered questionnaire. The Cox proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Results Although a history of diabetes mellitus was not associated with the risk of total prostate cancer in this population, after stratification based on the clinical stage of prostate cancer, patients with diabetes mellitus showed a higher risk of advanced prostate cancer with a multivariate adjusted HR = 1.89 (95% CI: 1.02-3.50). The relationship remained robust when we excluded from the analysis cases arising in the first 2 years. Conclusion This population-based prospective cohort study indicates that a history of diabetes mellitus is associated with an increased incidence of advanced prostate cancer.