Hypothesis disproved

A study involving 29 342 American males (aged 46-81) during a 8-year-period (1992-2000), published in this weeks issue of JAMA, seems to show that frequent ejaculation gives some protection against prostate cancer (PC). The result is rather remarkable, because the study was initially designed to find out whether frequent ejaculation could possibly be a contributing factor to prostate cancer. Surprisingly, it turned out to be the other way around, but only for individuals with very high ejaculation frequency.

Adding up the ejaculations

All of the 29 342 subjects were given intimate questions about their sex habits, regarding 1) their present sex habits, 2) their habits when they were between 20 and 29 years old, and 3) their habits when they were between 40 and 49 years old. All manners of achieving ejaculation were treated equally and added up -- intercourse, masturbation, wet dreams -- and the questions were repeated every second year throughout the period.

During the period of study 1449 new cases of PC were discovered among the subjects included in the study. 953 of these tumors were confined to the prostate, while 147 had spread into the surrounding tissue.

Encouraging results

The results can be summarized as follows (see Reference for the original results, which are presented as multivariate relative risks):

  • Ejaculation rate at age 20-29: HIGH compared to LOW -- 11% lower risk of PC
  • Ejaculation rate at age 40-49: HIGH compared to LOW -- 32% lower risk of PC
  • Ejaculation rate previous year: HIGH compared to LOW -- 51% lower risk of PC

(HIGH ejaculation frequency: > 20 ejaculations per month, LOW ejaculation frequency: 4-7 ejaculations per month)

Cautious researchers

The figures were obtained by trying to eliminate factors like age, heredity, sexually transmitted disease, smoking and eating habits by multivariate analysis. The researchers themselves are characteristically cautious, and conclude their article by saying: “Our results suggest that ejaculation frequency is not related to increased risk of prostate cancer”.

More sex, just to be on the safe side

Nevertheless, I suspect that most male readers of the study will increase their ejaculation frequency considerably, just to be on the safe side.


Michael F. Leitzmann, MD; Elizabeth A. Platz, ScD; Meir J. Stampfer, MD; Walter C. Willett, MD; Edward Giovannucci, MD: Ejaculation Frequency and Subsequent Risk of Prostate Cancer
JAMA (Journal of the American Medical Association).