More sexual partners, more cancer?

a couple’s feet poking out from under the sheets

Two headlines caught my eye recently:

The relationship between chronic diseases and number of sexual partners: an exploratory analysis

and

Study warns more sex might mean higher likelihood for cancer

It may be hard to believe, but both of these refer to same medical research. I’m not sure which one I like better. The first one is the actual title of the research, which provides no information about its findings. The second one is a newspaper headline. It cuts right to the chase about the study’s main findings. While it’s much more specific — and alarming — it is also misleading.

Is there a link between the number of sexual partners and cancer?

The study investigating this possibility was published BMJ Sexual & Reproductive Health. It enrolled about 2,500 men and 3,200 women who were 50 or older (average age 64). Each person was surveyed about the total number of sexual partners they’d had over the course of their lives. This information was compared with a number of medical conditions they’d developed, including cancer, heart disease, and stroke.

The study demonstrated that

Men who reported 10 or more sexual partners in their life were nearly 70% more likely to have developed cancer when compared with those reporting 0 or 1 lifetime sexual partners.
For women, the findings were even more dramatic: women who reported 10 or more sexual partners in their life were nearly 91% more likely to have developed cancer when compared with those reporting 0 or 1 lifetime sexual partners.

Men were more likely than women to report having at least 10 partners (22% of men vs. 8% of women) while women were more likely to have fewer partners (41% of women and 28.5% of men reporting having had 0 to 1 partners).

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It’s worth noting this study was performed in England with health information initially collected in the late 1990s. The results could have been different if researchers had assessed risk of a different population or at a different point in time. In addition, self-reporting was relied upon to assess sexual behavior, and it’s possible the reported number of sexual partners and other health behaviors were not accurate.

Does this mean having sex leads to cancer?

The answer is almost surely no.

That’s because this type of study cannot assess whether sex causes cancer. It can only determine whether there is a correlation between the two. Also, we already know of ways that sexual behavior can indirectly affect cancer risk without actually causing cancer, especially through sexually transmitted infections. Some of the strongest connections are for:

human papilloma virus (HPV), which increases the risk of cancers of the cervix, mouth, penis, and anus
human immunodeficiency virus (HIV) infection, which increases the risk of cancers such as Kaposi’s sarcoma and lymphoma
hepatitis B and hepatitis C infection, which have been linked to liver cancer
gonorrhea, which increases the risk of prostate cancer (particularly among African American men).

In addition, people with more sexual partners tended to smoke more and drink more alcohol. These factors could, themselves, increase the risk of cancer. So, certain factors — in these cases, infections, smoking, and drinking — could have an impact on cancer risk, rather than having sex or the number of sexual partners.

While future research could find previously unidentified risks in having a higher number of sexual partners, we already know enough to explain the connection.

The bottom line

While it may be tempting to conclude from this new research that limiting the number of sexual partners you have will lower your risk of cancer, I think that would be a misinterpretation of the data. The better take-home message would be to take precautions to avoid sexually transmitted diseases and pursue other proven strategies to lower your cancer risk, including stopping smoking and limiting alcohol.