LAUSR

Use of vitamin K antagonists (VKAs) has been suggested to reduce the risk of prostate cancer. We conducted a nested case–control study using Danish demographic and health data registries and summarized existing evidence in a meta‐analysis. The case–control study included all Danish men aged 40–85 years with incident histologically verified prostate adenocarcinoma between 2005 and 2015 (cases). For each case, we selected 10 age–matched controls. We used conditional logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CI) for prostate cancer associated with long–term VKA use adjusted for concomitant drug use, medical history and socioeconomic status. Among 38,832 prostate cancer cases, 1,089 (2.8%) had used VKAs for 3 or more years compared to 10,803 (2.8%) controls yielding a crude OR of 1.01 (95% CI, 0.95–1.08). Multivariable adjustment for covariates had limited influence on the association (OR, 1.03; 95% CI, 0.97–1.10). We observed no dose–response relationship (e.g. OR for 5–10 years of use, 1.06 95% CI, 0.97–1.16). We included 8 studies in the meta–analysis reporting effect estimates from 0.51 (95% CI, 0.23–1.13) to 1.10 (95% CI, 0.94–1.40). Using random effect methods, a pooled effect estimate of 0.86 (95% CI, 0.70–1.05) was obtained; however, there was considerable across–study heterogeneity (I2: 93.9%). In conclusion, we did not observe a reduced risk of prostate cancer associated with VKA use in this nationwide study and, taken together with previous study findings, a major protective effect of VKAs against prostate cancer seems unlikely.