Diabetes associated with reduced risk of prostate cancer

The results of a study published in the January 15th issue of the American Journal of Epidemiology suggest an association between diabetes type 2 and a reduced risk of prostate cancer. However, this is only observed several years after diabetes diagnosis.

“One previous study has suggested that diabetes may decrease risk of prostate cancer but only several years after diagnosis of diabetes,” Dr. Carmen Rodriguez and colleagues from the American Cancer Society in Atlanta note.The researchers examined the relationship between the time of diabetes diagnosis and the risk of prostate cancer in men enrolled in the Cancer Prevention Study II Nutrition Cohort. Subjects completed a mailed questionnaire regarding information on diabetes at baseline in 1992 and at follow-up in 1997 and 1999. The team also used data available from a previous study in 1982.Through August 31, 2002, a total of 5318 cases of incident prostate cancer were documented among 72,670 men. A total of 10,053 men (13.8%) reported a history of physician-diagnosed diabetes. Of these, 1643 (16.3%) reported using insulin injections.”Self-reported diabetes was associated with lower prostate cancer incidence rates after adjustment for age, race, education, and prostate-specific antigen testing (rate ratio (RR) = 0.67),” the researchers report.Men who were diagnosed with diabetes within the last 3 years had slightly higher rates of prostate cancer compared to nondiabetic men (RR = 1.23). However, in men who had diabetes for at least 4 years, the rate of prostate cancer was lower than in nondiabetic men (RR = 0.63).”Our results are consistent with the hypothesis that risk of prostate cancer differs by time since diagnosis of diabetes,” Dr. Rodriguez’s team concludes. The data also “provide limited support for a role of insulin and testosterone in prostate carcinogenesis.”(Source: Am J Epidemiol 2005;161:147-152: Reuters Health: Oncolink: January 2005.)