Murtola TJ et al. (2008) Antidiabetic medication and prostate cancer risk: a population-based case-control study. Am J Epidemiol [doi:10.1093/aje/kwn190]

The decreased risk of prostate cancer observed in some studies of men with diabetes has previously been suggested to be the result of a possible effect of the use of antidiabetic medications. In the first study of its kind, Murtola et al. have evaluated the risk of prostate cancer in men receiving antidiabetic drugs.

The authors identified all incident prostate cancer cases in Finland between 1995 and 2002 from the Finnish Cancer Registry, which were matched with controls randomly selected by the Population Register Center of Finland to produce 24,723 matched case–control pairs. Medication use by the study population during this period was established using the nationwide prescription database of the Social Insurance Institution of Finland.

The risk of prostate cancer was lower in men using any antidiabetic drug than in those not receiving such medication (odds ratio 0.89, 95% CI 0.84–0.94). This association was strengthened when the analysis was adjusted for age, place of residence and use of other medications commonly prescribed along with antidiabetic drugs (e.g. aspirin, cholesterol-lowering drugs or antihypertensive drugs; odds ratio 0.84, 95% CI 0.79–0.90). Overall prostate cancer risk correlated inversely with amount of oral drugs or insulin used and duration of medical treatment.

Given that a reduction in prostate cancer risk was seen in men receiving multiple oral antidiabetic drugs and also in insulin users, the association between diabetes and low prostate cancer risk is probably not an effect of antidiabetic drug therapy but rather of the underlying diabetes itself.