title: Risk factors associated with endometriosis: importance of study population for characterizing disease in the ENDO Study.
abstract: OBJECTIVE
  We sought to identify risk factors for endometriosis and their consistency across study populations in the Endometriosis: Natural History, Diagnosis, and Outcomes (ENDO) Study.
  
  
  METHODS
  In this prospective matched, exposure cohort design, 495 women aged 18-44 years undergoing pelvic surgery (exposed to surgery, operative cohort) were compared to an age- and residence-matched population cohort of 131 women (unexposed to surgery, population cohort). Endometriosis was diagnosed visually at laparoscopy/laparotomy or by pelvic magnetic resonance imaging in the operative and population cohorts, respectively. Logistic regression estimated the adjusted odds ratios (AORs) and 95% confidence intervals (CIs) for each cohort.
  
  
  RESULTS
  The incidence of visualized endometriosis was 40% in the operative cohort (11.8% stage 3-4 by revised criteria from the American Society for Reproductive Medicine), and 11% stage 3-4 in the population cohort by magnetic resonance imaging. An infertility history increased the odds of an endometriosis diagnosis in both the operative (AOR, 2.43; 95% CI, 1.57-3.76) and population (AOR, 7.91; 95% CI, 1.69-37.2) cohorts. In the operative cohort only, dysmenorrhea (AOR, 2.46; 95% CI, 1.28-4.72) and pelvic pain (AOR, 3.67; 95% CI, 2.44-5.50) increased the odds of diagnosis, while gravidity (AOR, 0.49; 95% CI, 0.32-0.75), parity (AOR, 0.42; 95% CI, 0.28-0.64), and body mass index (AOR, 0.95; 95% CI, 0.93-0.98) decreased the odds of diagnosis. In all sensitivity analyses for different diagnostic subgroups, infertility history remained a strong risk factor.
  
  
  CONCLUSIONS
  An infertility history was a consistent risk factor for endometriosis in both the operative and population cohorts of the ENDO Study. Additionally, identified risk factors for endometriosis vary based upon cohort selection and diagnostic accuracy. Finally, endometriosis in the population may be more common than recognized.
authors: Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City, UT 84132, USA. c.matthew.peterson@hsc.utah.edu
authors: C Matthew
authors: CM
authors: Peterson
authors: Erica B
authors: EB
authors: Johnstone
authors: Ahmad O
authors: AO
authors: Hammoud
authors: Joseph B
authors: JB
authors: Stanford
authors: Michael W
authors: MW
authors: Varner
authors: Anne
authors: A
authors: Kennedy
authors: Zhen
authors: Z
authors: Chen
authors: Liping
authors: L
authors: Sun
authors: Victor Y
authors: VY
authors: Fujimoto
authors: Mary L
authors: ML
authors: Hediger
authors: Germaine M
authors: GM
authors: Buck Louis
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D015331:Cohort Studies; D004412:Dysmenorrhea / Q000150:complications; D004715:Endometriosis / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D020073:Gravidity; D006801:Humans; D015994:Incidence; D007246:Infertility / Q000150:complications*; D010535:Laparoscopy; D007813:Laparotomy; D016015:Logistic Models; D008279:Magnetic Resonance Imaging; D016017:Odds Ratio; D010298:Parity; D017699:Pelvic Pain / Q000150:complications; D010388:Pelvis / Q000601:surgery*; D011247:Pregnancy; D011446:Prospective Studies; D012307:Risk Factors; D055815:Young Adult