title: Association of vasectomy and prostate cancer among men in a Maryland cohort.
abstract: OBJECTIVE
  To evaluate the association of vasectomy with prostate cancer.
  
  
  METHODS
  Participants were male members of the CLUE II cohort followed since 1989. On a questionnaire mailed in 1996, the men were asked if they had had a vasectomy and their age at vasectomy. Between 1996 and April 2004, 78 prostate cancer cases were confirmed among the 3373 men who were at least 35 years old at baseline and who completed the questions about vasectomy. Cox proportional hazards regression was used to estimate age-adjusted hazard ratios (HR) of prostate cancer.
  
  
  RESULTS
  The HR for prostate cancer for men who had had a vasectomy was 2.03 (95% CI: 1.24-3.32). Risk of low-grade disease (HR=2.87; 95% CI 1.49-5.54), but not high-grade disease (HR=0.99; 95% CI 0.36-2.76), was higher in men who had had a vasectomy. No statistically significant associations were observed for low- or high-stage disease. The association for vasectomy was more pronounced in men who were 40 years at the time of vasectomy (HR=2.63; 95% CI 1.40-4.94) than in men who were younger at vasectomy.
  
  
  CONCLUSIONS
  The results from this prospective study suggest a positive association between vasectomy and prostate cancer, especially low-grade disease.
authors.affiliation: Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, 615 N. Wolfe St., Room E6138, Baltimore, MD 21205, USA.
authors.forename: Sabine
authors.initials: S
authors.lastname: Rohrmann
authors.forename: Dina N
authors.initials: DN
authors.lastname: Paltoo
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Platz
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Hoffman
authors.forename: George W
authors.initials: GW
authors.lastname: Comstock
authors.forename: Kathy J
authors.initials: KJ
authors.lastname: Helzlsouer
mesh_terms: D000328:Adult; D000367:Age Factors; D006801:Humans; D008297:Male; D008396:Maryland / Q000453:epidemiology; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000473:pathology; D011795:Surveys and Questionnaires; D014659:Vasectomy