RESULTSThere  was no association of prostate cancer with the number of sexual  partners or with the maximum number of ejaculations in 24 h. There was a  negative trend (
P < 0.01) for the association between risk  and number of ejaculations in the third decade, independent of those in  the fourth or fifth. Men who averaged five or more ejaculations weekly  in their 20s had an odds ratio (95% confidence interval) of 0.66  (0.49–0.87) compared with those who ejaculated less often.
CONCLUSIONSThe  null association with the number of sexual partners argues against  infection as a cause of prostate cancer in this population. Ejaculatory  frequency, especially in early adult life, is negatively associated with  the risk of prostate cancer, and thus the molecular biological  consequences of suppressed or diminished ejaculation are worthy of  further research.