Does Sexual Activity Affect My Risk of Cancer?

What does sex have to do with prostate cancer? Could a man’s sexual activity have any repercussions—one way or the other—on his risk of getting prostate cancer?

In the past, scientists considering this question have come up with good but conflicting theories, says epidemiologist Elizabeth A. Platz, Sc.D. Some researchers speculate that men who have sex more often “may be more likely to acquire a sexually transmitted disease, which may infect the prostate, cause inflammation and other damage, and increase the risk of prostate cancer.” (For more on the growing link between inflammation and prostate cancer, read story ) Another thought is that men who have sex more often have a higher sex drive, because of a higher level of male hormones—which, in turn, may increase the risk of prostate cancer.

But other researchers believe that sexual activity may actually decrease the risk of prostate cancer—that regular ejaculation, if you will, “cleans house” in the prostate, making it a less welcome harbor for cancer-causing agents, infection, and stagnant materials that could lead to inflammation.

Previous studies have been inconclusive, notes Platz, but “taken together, they hint that men who have more sex, or who have had a sexually transmitted disease, are more likely to have prostate cancer.”

Platz and her colleagues at Harvard and the National Cancer Institute were unconvinced. As part of a massive study, led by epidemiologist Michael Leitzmann at Harvard, they recently studied nearly 30,000 men participating in the Health Professionals Follow-up Study. Most of these men were white and middle-aged, and very few had ever had a sexually transmitted disease. “In 1992, we asked the men who did not have prostate cancer to report their typical number of ejaculations per month in their twenties, forties, and during the past year,” says Platz.

Over the next eight years, nearly 1,500 of these men went on to develop prostate cancer.

The scientists found that men who reported more ejaculations—more than 21 a month, on average across their adult life—had twothirds the lifetime risk of prostate cancer of men who reported fewer (4 to 7) ejaculations a month. Notes Platz: “Compared with men reporting fewer ejaculations per month at all ages, men who reported 21 or ejaculations per month had one-fourth the risk of prostate cancer.”

Certain important features of this study make these observations more credible, she adds. One is the sheer number of men involved; another is “the fact that the men reported their ejaculation frequency well before they were diagnosed with prostate cancer.” Also, the scientists were able to rule out such factors as a man’s history of sexually transmitted diseases, which could have clouded the results.

Another recent study of many men, with and without prostate cancer, has produced similar findings, says Platz. “Based on these two large, well-conducted studies, men should not be worried that frequent ejaculation will cause prostate cancer.” The next step, she adds, is to figure out why frequent ejaculation seems to have this protective effect, and the role inflammation plays here.