Women who have had 10 or more sexual partners do not double their risk of getting cancer

"Having sex with 10 people in your lifetime ‘increases cancer risk by 90%'"

The Sun, 13 February 2020

"Women who have had 10 or more sexual partners face DOUBLE the risk of cancer because of STIs and because promiscuous people drink and smoke more, study claims"

Mail Online, 14 February 2020

Claims that having 10 or more sexual partners in a lifetime increases the cancer risk for women by 91% are unfounded. A study did find that women who had 10 or more sexual partners were also more likely to have had cancer than those with one or no partners, but it didn’t establish that one caused the other.

The researchers also did not take several relevant factors into account.

The study looked at the number of lifetime sexual partners and different health outcomes amongst more than 5,000 adults living in England and over the age of 50.

The data used was from the 2012/13 English Longitudinal Study of Ageing, and relied on participants to honestly report their number of sexual partners, health issues and things like whether they currently smoked, how much alcohol they drank and how much exercise they did.

Of the women, around 8% had had 10 or more sexual partners in their lifetime. 41% said they’d had zero or one. For men, 22% said they’d had 10 or more sexual partners, and 29% had zero or one.

The study found that, among women, those who said they’d had 10 or more sexual partners in their lifetime had 91% higher odds of reporting a diagnosis of cancer than those with zero or one partner. There was no statistically significant difference between those reporting zero or one partner and those reporting up to nine partners.

For men, those with 10 or more sexual partners were 69% more likely to report a cancer diagnosis than those with zero or one. And those with two to four partners were 57% more likely.

Correlation is not causation

The researchers made clear in their study that they could not show higher number of sexual partners caused the cancer diagnoses. They did suggest greater potential exposure to sexually transmitted diseases and human papillomavirus (HPV)—which can cause some cancers—could be linked.

However, the study also found those with the highest numbers of sexual partners were more likely to report they smoked and drink alcohol frequently, things we know definitely do increase the risk of cancer.  The study did not collect any information on whether participants had STIs, or on other potential risk factors for cancer such as weight, previous smoking or drinking habits or family cancer history.

This means that the study doesn’t show whether the number of sexual partners itself increases cancer risk, or whether it’s simply associated with other risk factors which do increase cancer risk.

Natasha Paton, health information manager at Cancer Research UK, said “There wasn’t a significant clear and steady increase in the risk of cancer as the number of partners increased – so we cannot say whether the findings they observed were directly connected or merely chance.

“Overall, the evidence is not strong enough to support the headlines that having more than 10 sexual partners definitively increases women’s risk of cancer by 90%, or almost double.”

She added that it was “speculation” to suggest an increased cancer risk could be because of STIs or HPV in those with a higher number of sexual partners without actually gathering data on how many participants had these infections.

The study itself noted that the association found between number of sexual partners and cancer could be “a chance finding” and further research was needed to establish whether a causal relationship exists.