Vasectomy and prostate cancer risk: a 38-year nationwide cohort study.

A man's risk of prostate cancer has been linked to his prior reproductive history, with low sperm quality, low ejaculation frequency, and a low number of offspring being associated with increased prostate cancer risk. It is however highly controversial whether vasectomy, a common sterilization procedure for men, influences prostate cancer risk.

We established a cohort of all Danish men (born from 1937) and linked information on vasectomy, doctor visits, socioeconomic factors and cancer from nationwide registries using unique personal identification numbers. Incidence risk ratios for prostate cancer by time since vasectomy and age at vasectomy during the follow-up were estimated using log-linear Poisson regression.

Overall, 26,238 cases of prostate cancer occurred among 2,150,162 Danish men during 53.4 million person-years of follow-up. Overall, vasectomized men had an increased risk of prostate cancer compared with non-vasectomized men (relative risk 1.15; 95% CI, 1.10 to 1.20). The increased risk of prostate cancer following vasectomy persisted for at least 30 years after the procedure and was observed regardless of age at vasectomy and cancer stage at diagnosis. Adjustment for the number of visits to doctor and socioeconomic factors did not explain the association.

Vasectomy is associated with a statistically significant increased long-term risk of prostate cancer. The absolute increased risk following vasectomy is nevertheless small, but our finding supports a relationship between reproductive factors and prostate cancer risk.

Journal of the National Cancer Institute. 2019 May 23 [Epub ahead of print]

Anders Husby, Jan Wohlfahrt, Mads Melbye

Department of Epidemiology Research, Statens Serum Institut, DK-2300 Copenhagen, Denmark.