A study of 72,000 men enrolled in the Cancer Prevention Study II found that men with type 2 diabetes are less prone to prostate cancer. The purpose of the study was to examine the relationship between the time of the diabetes diagnosis and the risk of prostate cancer. For the study, the participants completed a questionnaire regarding information on diabetes at the study's onset in 1992 and at follow-up in 1997 and 1999. In 2002, 5318 men had been diagnosed with prostate cancer, and 10,053 men reported a physician diagnosis of diabetes.
"Diabetes was associated with lower prostate cancer incidence rates after adjustment for age, race, education, and prostate-specific antigen testing," reported the researchers in the American Journal of Epidemiology (January 15, 2005). The results of the study showed that men who were diagnosed with diabetes within the last 3 years had slightly higher rates of prostate cancer, compared with men without diabetes. On the other hand, the participants who had had diabetes for at least 4 years had a one-third lower rate of prostate cancer.