title: Vasectomy and risk of aggressive prostate cancer: a 24-year follow-up study.
abstract: OBJECTIVE
  Conflicting reports remain regarding the association between vasectomy, a common form of male contraception in the United States, and prostate cancer risk. We examined prospectively this association with extended follow-up and an emphasis on advanced and lethal disease.
  
  
  METHODS
  Among 49,405 U.S. men in the Health Professionals Follow-Up Study, age 40 to 75 years at baseline in 1986, 6,023 patients with prostate cancer were diagnosed during the follow-up to 2010, including 811 lethal cases. In total, 12,321 men (25%) had vasectomies. We used Cox proportional hazards models to estimate the relative risk (RR) and 95% CIs of total, advanced, high-grade, and lethal disease, with adjustment for a variety of possible confounders.
  
  
  RESULTS
  Vasectomy was associated with a small increased risk of prostate cancer overall (RR, 1.10; 95% CI, 1.04 to 1.17). Risk was elevated for high-grade (Gleason score 8 to 10; RR, 1.22; 95% CI, 1.03 to 1.45) and lethal disease (death or distant metastasis; RR, 1.19; 95% CI, 1.00 to 1.43). Among a subcohort of men receiving regular prostate-specific antigen screening, the association with lethal cancer was stronger (RR, 1.56; 95% CI, 1.03 to 2.36). Vasectomy was not associated with the risk of low-grade or localized disease. Additional analyses suggested that the associations were not driven by differences in sex hormone levels, sexually transmitted infections, or cancer treatment.
  
  
  CONCLUSIONS
  Our data support the hypothesis that vasectomy is associated with a modest increased incidence of lethal prostate cancer. The results do not appear to be due to detection bias, and confounding by infections or cancer treatment is unlikely.
authors.forename: Mohummad Minhaj
authors.initials: MM
authors.lastname: Siddiqui
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Wilson
authors.forename: Mara M
authors.initials: MM
authors.lastname: Epstein
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Rider
authors.forename: Neil E
authors.initials: NE
authors.lastname: Martin
authors.forename: Meir J
authors.initials: MJ
authors.lastname: Stampfer
authors.forename: Edward L
authors.initials: EL
authors.lastname: Giovannucci
authors.forename: Lorelei A
authors.initials: LA
authors.lastname: Mucci
mesh_terms: D000328:Adult; D000368:Aged; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology*; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D014659:Vasectomy / Q000009:adverse effects*