title: Ejaculation frequency and subsequent risk of prostate cancer.
abstract: BACKGROUND
  Sexual activity has been hypothesized to play a role in the development of prostate cancer, but epidemiological data are virtually limited to case-control studies, which may be prone to bias because recall among individuals with prostate cancer could be distorted as a consequence of prostate malignancy or ongoing therapy.
  
  
  OBJECTIVE
  To examine the association between ejaculation frequency, which includes sexual intercourse, nocturnal emission, and masturbation and risk of prostate cancer.
  
  
  METHODS
  Prospective study using follow-up data from the Health Professionals Follow-up Study (February 1, 1992, through January 31, 2000) of 29 342 US men aged 46 to 81 years, who provided information on history of ejaculation frequency on a self-administered questionnaire in 1992 and responded to follow-up questionnaires every 2 years to 2000. Ejaculation frequency was assessed by asking participants to report the average number of ejaculations they had per month during the ages of 20 to 29 years, 40 to 49 years, and during the past year (1991).
  
  
  METHODS
  Incidence of total prostate cancer.
  
  
  RESULTS
  During 222 426 person-years of follow-up, there were 1449 new cases of total prostate cancer, 953 organ-confined cases, and 147 advanced cases of prostate cancer. Most categories of ejaculation frequency were unrelated to risk of prostate cancer. However, high ejaculation frequency was related to decreased risk of total prostate cancer. The multivariate relative risks for men reporting 21 or more ejaculations per month compared with men reporting 4 to 7 ejaculations per month at ages 20 to 29 years were 0.89 (95% confidence interval [CI], 0.73-1.10); ages 40 to 49 years, 0.68 (95% CI, 0.53-0.86); previous year, 0.49 (95% CI, 0.27-0.88); and averaged across a lifetime, 0.67 (95% CI, 0.51-0.89). Similar associations were observed for organ-confined prostate cancer. Ejaculation frequency was not statistically significantly associated with risk of advanced prostate cancer.
  
  
  CONCLUSIONS
  Our results suggest that ejaculation frequency is not related to increased risk of prostate cancer.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Md 20892, USA. leitzmann@mail.nih.gov
authors.forename: Michael F
authors.initials: MF
authors.lastname: Leitzmann
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Platz
authors.forename: Meir J
authors.initials: MJ
authors.lastname: Stampfer
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.forename: Edward
authors.initials: E
authors.lastname: Giovannucci
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004542:Ejaculation; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D012307:Risk Factors