In September 2018 researchers from China published their review of the medical scientific literature to assess the association between number of female sexual partners, age at first intercourse, ejaculation frequency and the risk of prostate cancer. A total of 22 studies involving 55,490 individuals (14,976 individuals with prostate cancer and 40,514 controls) were included in the review. Results showed that as the number of female sexual partners increased so did the risk of prostate cancer. It was also seen that the risk of prostate cancer was decreased by 4% for every 5-year delay in age at the time of first intercourse. In addition, it was also observed that moderate ejaculation frequency (2-4 times per week) appeared to be significantly associated with a lower risk of prostate cancer.
Jian Z et al. Sexual Activity and Risk of Prostate Cancer: A Dose-Response Meta-Analysis. J Sex Med. 2018 Sep;15(9):1300-1309