CHAMPAIGN, Ill. -- Men should already know that sex with multiple partners, especially unprotected sex, can increase their risk of contracting HIV and various venereal diseases.

They also can add that it may raise their odds of getting prostate cancer in middle age, according to a study published in a recent issue of the American Journal of Epidemiology.

The study, titled "Sexual Factors and the Risk of Prostate Cancer," was written by Karin Rosenblatt, a professor of community health at the University of Illinois; and Janet Stanford and Kristine Wicklund, researchers in the Program in Epidemiology at the Fred Hutchinson Cancer Research Center in Seattle. In it, the authors wrote that their findings "suggest that there is a direct positive relationship between the number of lifetime female sexual partners and the risk of prostate cancer in middle-aged men." The findings are consistent with several previous studies, they noted, and "suggest that sexual behavior and associated exposure to sexually transmitted agents enhance the risk of prostate cancer." The study was based on a population-based interview survey of 1,456 men ages 40-64 in King County, Wash. The study group consisted of 753 men who had been diagnosed with prostate cancer between 1993 and 1996. They were identified by the Seattle-Puget Sound cancer registry, part of the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program.

The control group of 703 men was chosen using random-digit telephone dialing, with an age distribution similar to that of the study group.

The analysis showed a linear relationship between risk and number of female sexual partners, with those having 30 or more sexual partners shown to have more than twice the risk of having prostate cancer. (The respondents were asked to estimate their number of partners within the following ranges: 1, 2-4, 5-14, 15-29, and 30 or more.)

The authors established that relationship after controlling for factors such as age, age at first intercourse, race, family history of prostate cancer, and number of prostate specific antigen (PSA) tests in the past five years. They found no relationship between prostate cancer and frequency of intercourse.

Rosenblatt pointed out that though the numbers were cause for concern, they should not be overplayed. "I'm not sure we've figured out the mechanism with this, and also some studies don't show any association and some studies do, so I think there needs to be a little more research in this area." Similar studies on other cancers, however, such as cervical cancer, have shown even greater risk with the increase in number of sexual partners.

###