A group of researchers from the University of Montreal and the INRS – Institut Armand-Frappier, have published their latest findings where they state that men who have sex with more than 20 women during their lifetime have a lower risk of being diagnosed with prostate cancer. On the contrary, having more than 20 male partners is associated with a twofold higher risk of developing the malignancy.
The study, published in the journal of Cancer Epidemiology by Marie-Elise Parent and Marie-Claude Rousseau, professors at university’s School of Public Health, and their colleague Andrea Spence, analyzed data from the Montreal study PROtEuS (Prostate Cancer & Environment Study), where 3,208 men filled a questionnaire that included question regarding their sex lives. Among these men, 1,590 were diagnosed with prostate cancer and 1,618 men were included as controls.
Researchers found that men diagnosed with prostate cancer, had twice the chance of having a relative with cancer. Surprisingly, the number of sexual partners was tightly linked with the probabilities of developing prostate cancer.
Men who had never had sexual intercourse were more likely to develop this malignancy when compared to those who had.
Furthermore, if a man had more than 20 different female sexual partners, they had a 28% lower risk of developing any type of prostate cancer, along with a 19% reduction for particularly aggressive types of cancer.
“It is possible that having many female sexual partners results in a higher frequency of ejaculations, whose protective effect against prostate cancer has been previously observed in cohort studies,” Dr. Parent explained in a University of Montreal news release.
There have been previous studies suggesting the mechanisms behind this observed protective effect lies either within the reduction of cancer-causing substances in prostatic fluid or through decreased production of intraluminal crystalloids.
Even though only 12% of participants admitted having at least one sexually transmitted infection (STI), this was not an influencing factor in the probability of developing prostate cancer.
Although having only one male partner did not affect the risk of prostate cancer, having more than 20 male partners doubled the risk for this malignancy and increased by 500% the risk of having a less aggressive type of prostate cancer.
Nonetheless, the hypotheses underlying these results are highly speculative. According to Dr. Parent, “It could come from greater exposure to STIs, or it could be that anal intercourse produces physical trauma to the prostate”.
“We were fortunate to have participants from Montreal who were comfortable talking about their sexuality, no matter what sexual experiences they have had, and this openness would probably not have been the same 20 or 30 years ago,” Dr. Parent explained. “Indeed, thanks to them, we now know that the number and type of partners must be taken into account to better understand the causes of prostate cancer.”