A study conducted by researchers at the American Cancer Society, published in the 2005 January 15 issue of the American Journal of Epidemiology, has concluded that men with type 2 diabetes were less likely to develop prostate cancer than men without diabetes. Results of the study, using data from some 72,000 men, indicated that the risk of prostate cancer was linked to the length of time since diagnosis of diabetes. Men with diabetes for at least four years had a one-third lower rate of prostate cancer.
Results of the study
From the Department of Epidemiology and Surveillance Research, American Cancer Society, Atlanta, GA.
One previous study has suggested that diabetes may decrease risk of prostate cancer but only several years after diagnosis of diabetes. The authors examined the role of timing of diabetes diagnosis in relation to risk of prostate cancer among men in the Cancer Prevention Study II Nutrition Cohort. Participants in the study completed a mailed questionnaire including information on diabetes at enrollment in 1992 and at follow-up questionnaires in 1997 and 1999. Historical information on diabetes was also available from a previous study in 1982. The authors documented 5,318 cases of incident prostate cancer through August 31, 2001, among 72,670 men. Results from Cox proportional hazards models showed that diabetes was associated with a lower incidence of prostate cancer (rate ratio (RR) = 0.67, 95% confidence interval (CI): 0.60, 0.75). This association differed significantly by time since diagnosis of diabetes (p < 0.0002); risk of prostate cancer was slightly increased during the first 3 years after diagnosis of diabetes (RR = 1.23, 95% CI: 0.92, 1.65) but was reduced among men diagnosed 4 or more years before (RR = 0.63, 95% CI: 0.56, 0.71). Study results are consistent with the hypothesis that diabetes is associated with reduced risk of prostate cancer but only several years after diagnosis of diabetes.