MedicalResearch.com Interview with: Jennifer R. Rider, ScD, MPH Assistant Professor of Medicine Channing Division of Network Medicine Brigham and Women's Hospital and Harvard Medical School Department of Epidemiology Harvard T.H. Chan School of Public Health Boston, MA 02115 Medical Research: What is the background for this study? What are the main findings? Dr. Rider: Numerous studies have investigated the potential role of sexual activity on the development of prostate cancer. However, most of these studies have been small and retrospective, making them more prone to bias. In addition, previous studies often relied on proxies of exposure for sexual activity (number of sexual partners, age at first marriage, etc.), which may not adequately measure the aspects of sexual activity that are most important for prostate health. The current study is the largest prospective study to date on ejaculation frequency and prostate cancer. It includes 18 years of follow up of almost 32,000 healthy men, 3839 of whom later were diagnosed with prostate cancer.  We asked men about their average monthly frequency of ejaculation between the ages of 20-29, 40-49, and in the year prior to the questionnaire (1991). We find that frequency of ejaculation throughout life course is inversely associated with risk of prostate cancer at all three of these time points. For instance, men who have an average monthly ejaculation frequency of 21 or more times/moth at ages 40-49 have a statistically significant 22% reduction in risk of developing prostate cancer compared to men with a frequency of 4-7 times/month, adjusting for multiple dietary and lifestyle factors, and prostate cancer screening history. (more…)