It has been postulated that sexual activity may be a risk factor for prostate cancer. For example, increased sexual activity may indirectly increase prostate cancer risk through infectious disease acquisition, or retained secretions may harbor carcinogenic materials in men with decreased sexual activity. Leitzmann and colleagues used self-reported number of ejaculations to determine prospectively if ejaculation frequency is associated with prostate cancer risk.

Participants in the Health Professionals Follow-up Study completed a questionnaire every two years with questions on ejaculation frequency, beginning in 1992. Participants were to estimate their ejaculation frequency at ages 20 to 29, 40 to 49, and in the previous year. The study’s major end point was total prostate cancer incidence. The relative risk of prostate cancer was calculated after controlling for multiple other factors, such as body mass index, smoking, and dietary habits.

A total of 1,449 men were diagnosed with prostate cancer during 222,426 person-years of follow-up. Ejaculation frequency generally was unrelated to prostate cancer risk. However, men with the highest frequency of ejaculations had a slightly decreased risk, with each three ejaculations per week reducing lifetime total prostate cancer risk by 15 percent. Men with the lowest ejaculation frequency at ages 40 to 49 and across their lifetimes had a lower relative risk. Although these findings were maintained if the analysis was restricted to organ-confined prostate cancer, intermediate frequency of ejaculation at ages 40 to 49 was associated with a lower risk of advanced prostate cancer.

Having a greater frequency of ejaculations did not increase prostate cancer risk. On the contrary, very frequent ejaculations might decrease total prostate cancer and organ-confined cancer risk. In addition, there was a decrease in prostate cancer risk in patients with the lowest ejaculation frequencies. The mechanisms mediating these findings are unknown.