Prostate cancer (PCA) is a common malignancy among men, influenced by genetics, lifestyle, and socioeconomic factors. The role of sexual activity, including age of first sexual intercourse, sexual orientation, and number of sexual partners, in PCA risk remains controversial. The objective was to evaluate the association between various sex-related behaviors and the incidence of prostate cancer.

In this prospective cohort study, we analyzed data from the UK Biobank (UKB). A total of 136,047 male participants free of prostate cancer at baseline were included. We focused on age at first intercourse, number of lifetime sexual partners, sexual orientation and same-sex experience. Cox proportional hazards regression analysis was used to estimate the association between sex-related behaviors and prostate cancer incidence.

During a mean follow-up of 13.11 years, 7,666 (5.60%) incident PCA cases were recorded. Among the 136,047 participants with a mean age of 55.67 years, the risk of prostate cancer was lower among those who had their first sexual intercourse at a later age [Q4 vs. Q1 hazard ratio (HR), 0.89; 95% confidence interval (CI), 0.83-0.95], and higher among those who had more sexual partners [Q3 vs. Q1 HR, 1.09; 95% CI, 1.03-1.15; Q4 vs. Q1 HR, 1.08; 95% CI, 1.01-1.15]. Moreover, although a significant interaction with age stratification was detected (P for interaction < 0.05), sexual orientation and same-sex experience were not significantly associated with the risk of PCA.

Findings from this cohort study suggest that a later age at first sexual intercourse and fewer sexual partners may reduce the risk of developing PCA.