STIs are the main suspect in this increased risk of cancer, but people with more sex partners also tended to indulge in other risky behaviors, Smith noted.
“In our study, those with a greater number of sexual partners were more likely to smoke cigarettes and drink alcohol frequently, behaviors known to be associated with cancer risk,” Smith said. “It is possible that the number of sexual partners one has had captures a combination of likelihood of exposure to STIs and lifestyle profile.”
The study was published Feb. 13 in the journal BMJ Sexual & Reproductive Health.
Two U.S. health experts not involved with the study commented on the findings.
While interesting, this study has flaws that make it hard to draw meaningful conclusions about what it found, said Dr. Konstantin Zakashansky, an associate professor of obstetrics, gynecology and reproductive science with the Icahn School Medicine at Mount Sinai in New York City.
Sex and cancer are both touchy subjects, and it’s questionable whether one can trust people to accurately report either their promiscuity or their cancer diagnosis, Zakashansky said.
“The problem is people over-reporting, underreporting. You don’t know how truthful they are,” Zakashansky said. “There’s also recall bias, where they genuinely don’t remember.”
These are real problems with the study, agreed Mia Gaudet, scientific director of epidemiology research with the American Cancer Society.
But Gaudet said that the report does shine a spotlight on a potential cause of cancer that requires further research.
“The overall conclusions are consistent with what we know about the potential role of viruses in cancer, and support further study,” Gaudet said.
Human papillomavirus (HPV) has been linked to cervical, oral, anal and penile cancers, she noted, while hepatitis B and C are tied to liver cancer. It’s likely other viruses could be linked to other forms of cancer.
“Sexual health is something that’s understudied because of the taboos around it. While this study isn’t ideal, it’s helpful to have some information around this space,” Gaudet said.
In the meantime, people who’ve been promiscuous should talk with their doctor, Smith urged.
“People who had risky sexual encounters should contact their health care providers to get checked for potential sexually transmitted infectious and should discuss openly about how to minimize this risk,” Smith said. “Using appropriate protection will reduce the risk of related cancers going forward.”