Number of sexual partners linked to PCa risk

The number of sexual partners a man has could be related to risk of being diagnosed with prostate cancer, Canadian researchers report.

The results, which were published online in Cancer Epidemiology (Sept. 29, 2014), were obtained as part of the Montreal study PROtEuS (Prostate Cancer & Environment Study), in which 3,208 men responded to a questionnaire that included questions about their sex lives. Of these men, 1,590 were diagnosed with prostate cancer between September 2005 and August 2009, while 1,618 men formed the control group.

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The authors found that men who said they had never had sexual intercourse were almost twice as likely to be diagnosed with prostate cancer as those who said they had. In addition, compared to men who have had only one partner during their lifetime, having sex with more than 20 women was associated with a 28% lower risk of being diagnosed with the disease.

"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," said senior author Marie-Elise Parent, BSc, MSc, PhD, of the University of Montreal and INRS - Institut Armand-Frappier in a press release.

According to some studies, the underlying mechanism of this protective effect is in reducing the concentration of cancer-causing substances in prostatic fluid or lowering the production of intraluminal crystalloids. In all participants, the age at which they first had sexual intercourse or the number of sexually transmitted infections (STIs) they had contracted did not affect the risk of prostate cancer. Moreover, only 12% of all participants reported having had at least one STI in their lifetime, according to the authors.

The gender of the sexual partner appeared to have an effect on the link; having more than 20 male partners was associated with a twofold higher risk of getting prostate cancer compared to those who have never slept with a man. However, having only one male partner did not affect the risk of prostate cancer compared to those who have never had sexual intercourse with a man.

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