Researchers in the UK found that having 10 or more sexual partners over a lifetime almost doubled the risk of a woman developing cancer [1], and raised it by two thirds for men [2].
In addition, the study reported women with a higher number of sexual partners have heightened odds of a chronic health condition, though the same was not found in men.
The study, published in BMJ Sexual & Reproductive Health, draws on information from almost 6,000 respondents to an English longitudinal study on ageing.
As an observational study, it cannot establish cause. Nevertheless, the authors say their findings chime with those of previous studies implicating sexually transmitted infections in the development of several types of cancer and hepatitis.