Number of sexual partners, age at first intercourse, and ejaculation frequency appear to influence a man’s risk for prostate cancer, according to new research.

The notion that sexual activity might affect prostate cancer risk has been controversial. A meta-analysis published in 2002 reported that increased ejaculation frequency and having more sexual partners were associated with prostate cancer risk, but age at first intercourse was not.

Since then, more research has been conducted. The current study incorporated the newer studies and applied a dose-response analysis to the data to determine the roles of the above factors.

The research team searched relevant databases and identified twenty-two studies on the topic published through April 2018. Overall, the studies included 55,490 participants from nine countries. Most studies came from North America, but Europe, Australia, Asia, the Caribbean, and Cuba were also represented.

They found that men with fewer sexual partners were at lower risk for prostate cancer. For every 10 female partners the men had, their risk increased 1.10 fold.

First intercourse at an older age also seemed to lower prostate cancer risk, which was decreased 4% for every five years of delay.

The roles that number of sexual partners and age at first intercourse play might be explained by the “STIs hypothesis,” the authors said. Having an active sex life for a longer duration with many partners increases the likelihood of exposure to sexually transmitted infections and possibly “riskier lifestyle behaviors” which might contribute to cancer risk.

However, hormonal levels, injury, and inflammation might also be involved, the authors noted.

They added that moderate ejaculation frequency – two to four times a week – “might play a certain role in protecting from [prostate cancer].” They suggested several explanations for this finding. For example, frequent ejaculation might decrease the amount of carcinogens in prostatic fluid or curb the development of prostatic intraluminal crystalloids, which have been linked to prostate cancer.

Geography and culture may also influence prostate cancer risk. The authors explained that prostate cancer rates are lower in west and south Asia (e.g., India and Iran) than in the United States. Because of religious traditions, men in those cultures may be older at their first intercourse and have fewer sexual partners than their North American counterparts.

Additional research is needed to validate these findings, the authors said.

The study was published online in August as an article in press in the Journal of Sexual Medicine. 

Resources

•  The Journal of Sexual Medicine - “Sexual Activity and Risk of Prostate Cancer: A Dose–Response Meta-Analysis”
  Jian, Zhongyu MD, et al.
  (Full-text article in press. Published online: August 16, 2018)
  https://www.jsm.jsexmed.org/article/S1743-6095(18)31064-6/fulltext