30 Oct 2014
In - Sex Research

You may have seen this headline splashed across the papers today, but is the research it’s based on enough to suggest men should change their behavior? To put it bluntly, we don’t think so.

This isn’t the first time that sex and prostate cancer risk have been mentioned in the same sentence. In fact there have been a couple of previous studies suggesting that frequent sexual activity may be related to decreased prostate cancer risk.

The study that's hit the headlines this week was carried out by researchers at the University of Montreal in Canada as part of a larger study looking for environmental factors influencing men’s risk of developing prostate cancer.

The research team interviewed 1,590 men with prostate cancer and 1,618 men without prostate cancer and asked them about the number of both male and female sexual partners they’d had over their lifetime, as well as a number of other questions relating to their sexual history.

They found that men who reported never having had sex were almost twice as likely (194 per cent) to have been diagnosed with prostate cancer than men who said they had, which has been reported in some papers as ‘celibacy doubles the risk of the disease’. However, this result should be treated cautiously because, as the researchers themselves point out, the numbers are very low. Only 15 of the 1,590 prostate cancer cases and ten of the 1,618 non-prostate cancer controls said that they’d never had sexual intercourse - and the difference was not statistically significant.

The researchers also found that men who reported having sex with more than 20 women were 28 per cent less likely to have been diagnosed with prostate cancer compared to men who’d only had one female sexual partner. Some papers have also picked up on the finding that of the men diagnosed with prostate cancer, those who said they’d had more than 20 female sexual partners were 19 per cent less likely to have the aggressive form of the disease compared to men who’d only had one female sexual partner. However, again, this result is not statistically significant, so should be treated with caution.

The authors also noted that men who had more than 20 male sexual partners were almost twice as likely to have been diagnosed with prostate cancer as men who’d had only female sexual partners. However, once again, the number of men who said that they’d ever had a male sexual partner was low - only 78 of the 1,590 prostate cancer cases and 63 of the 1,618 non-prostate cancer controls. And the result was not statistically significant. It’s worth pointing out too, as many newspapers also did, that there was no association between risk of prostate cancer and men who said they’d had one male sexual partner.

One of the big problems with this type of research is that it relies on the people being interviewed remembering accurately, and telling the truth about, the number of sexual partners they’ve had over their lifetime. The researchers do note this as a limitation of their study, although they go on to say that the interviewers believed the majority of respondents (96 per cent) to be giving ‘truthful’ or ‘probably truthful’ responses.

Another point to note is that the men in this study were mainly Canadians of French descent, so we can’t say with certainty that the patterns observed in this population would be the same in any other population groups.

Finally, the most important caution message is that the researchers have spotted a link (correlation) between two things – number of sexual partners and risk of prostate cancer – but this is not the same as saying that one factor causes or prevents the other. We can’t say from this data that having multiple female sexual partners will prevent a man from getting prostate cancer, or that having two or more male partners will cause it.

So our take-home message is that while this is an eye-catching story, it’s incredibly difficult to draw any concrete conclusions on the association between the number of women a man has had sex with and his prostate cancer risk. And the results of this research should not encourage men to sleep with more women to protect themselves against the disease. Sorry guys.

It would be far more beneficial for men to familiarise themselves with the known risk factors for prostate cancer – being over 50 years old, having a family history of the disease, or being of Black ethnic origin. If you fall into any of these groups, it’s important that you speak to your GP about your risk.

The NHS choices website has also responded to the media frenzy around this research. Read what they have to say here.

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