A study published today claims to have found a link between having had ten or more sexual partners and an increased risk of cancer. But it’s not as simple as that.
While having a sexually transmissible infection (STI) can increase the risk of certain types of cancer, using a person’s lifetime number of sexual partners as a marker of their likely sexual health history is one of several flaws in this research.
The evidence from this study isn’t strong enough to conclude that having had multiple sexual partners increases a person’s risk of cancer.
Misinterpreting these findings could lead to stigma around STIs and having multiple sexual partners.
What the study did
The research, published in the journal BMJ Sexual & Reproductive Health, used data from 2,537 men and 3,185 women participating in the English Longitudinal Study of Ageing, a nationally representative study of adults aged 50+ in England.
The average age of participants was 64. Most were married or living with a partner, white, non-smokers, drank alcohol regularly, and were at least moderately active once a week or more.
Participants were asked to recall the number of people with whom they had ever had vaginal, oral or anal sex in their lifetime. The researchers grouped the responses into four categories shown in the table below.
The researchers then examined associations between lifetime number of sexual partners and self-reported health outcomes (self-rated health, limiting longstanding illness, cancer, heart disease and stroke).
The researchers controlled for a range of demographic factors (age, ethnicity, partnership status, and socioeconomic status) as well as health-related factors (smoking status, frequency of alcohol intake, physical activity, and depressive symptoms).
What the study found
Men with 2-4 partners and 10+ partners were more likely to have been diagnosed with cancer, compared to men with 0-1 partners. There was no difference between men with 0-1 partners and 5-9 partners.
Compared to women with 0-1 partners, women with 10+ partners were more likely to have been diagnosed with cancer.
Women with 5-9 partners and 10+ partners were also more likely to report a “limiting longstanding illness” than those with 0-1 partners.
The authors don’t specify what constitutes a limiting longstanding illness, but looking at the questions they asked participants, we can ascertain it’s a chronic condition that disrupts daily activities. It’s likely these ranged from mildly irritating to debilitating.
There was no association between number of sexual partners and self-rated general health, heart disease or stroke for either men or women.
Notably, while statistically significant, the effect size of all these associations was modest.