Prostate cancer strikes 232,000 American men annually and kills 30,000, numbers similar to the toll of breast cancer on women. Could sex boost men's risk? That disturbing possibility has been raised by several recent studies:
* Italian researchers found that compared with men who never married, those who did--and presumably had more sex--had significantly greater risk of prostate cancer. For men married more than twice, risk was three times that of never-married men.
* University of Illinois researchers correlated prostate cancer risk with men's age at first intercourse and estimated lifetime number of women sex partners. The younger the men became sexually active, the greater their risk. And the more sex partners they reported, once again, the greater their risk.
* And University of Iowa researchers found that as number of women sex partners increased, so did risk of prostate cancer, with men who reported sex more than three times a week showing the greatest risk.
On the other hand, the largest study shows just the opposite--that frequent sex protects against prostate cancer. Researchers at the National Cancer Institute asked 29,000 men, aged 46 to 81, to estimate their number of weekly ejaculations during their twenties, forties, and during the past year. Compared with men who reported seven or fewer ejaculations per month, men who experienced 21 or more were significantly less likely to develop prostate cancer.