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Metformin use and prostate cancer risk

Preston MA, Riis AH, Ehrenstein V, Breau RH, Batista JL, Olumi AF, Mucci LA, Adami HO et al.

European urology, 2014

122,260 participants

Abstract

BACKGROUND: Metformin may decrease prostate cancer (PCa) risk by reducing hyperinsulinemia-associated carcinogenesis or through direct effects on cancer cells.

OBJECTIVE: To evaluate the association between metformin use and PCa diagnosis.

DESIGN, SETTING, AND PARTICIPANTS: We used the Danish Cancer Registry and the Aarhus University Prescription Database to conduct a nested case-control study among men residing in northern Denmark from 1989 to 2011. We identified 12 226 cases of PCa and used risk-set sampling to select 10 population controls per case (n=122,260) from among men alive on the index date and born in the same year. A sensitivity analysis was conducted using subjects who had prostate-specific antigen (PSA) testing prior to 1 yr before the index date.

INTERVENTION: Metformin exposure was assessed using prescriptions redeemed before the index date.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression. The association between metformin use and PCa diagnosis was determined, controlling for diabetes severity and other potential confounders.

RESULTS AND LIMITATIONS: Metformin users were at decreased risk of PCa diagnosis compared with never-users (adjusted OR [aOR]: 0.84; 95% CI, 0.74-0.96). Diabetics on no medication (aOR: 0.98; 95% CI, 0.89-1.09) or on other oral hypoglycemics (aOR: 0.98; 95% CI, 0.86-1.10) did not have a reduced risk of PCa, while users of insulin did have a…

How strong is the evidence?

Evidence Hub reads this as a case-control, done in people. Its evidence level is 4 of 5 (Low · observational). Observational designs can show an association but not prove cause. Reported size: 122,260 participants or records.

How the five levels of evidence work. The level is assigned automatically from the abstract and can be wrong, so check the paper.

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