title: Endometriosis and mammographic density measurements in the Nurses' Health Study II.
abstract: Endometriosis and mammographic density have been hypothesized to be influenced by sex steroid hormonal exposures in adolescence and early adulthood. We investigated the association between endometriosis and mammographic density, a consistent and independent risk factor for breast cancer.
  
  
  
  We conducted a cross-sectional analysis among 1,581 pre- and postmenopausal women not previously diagnosed with breast cancer in the Nurses' Health Study II cohort. We measured average percent mammographic density and absolute dense and non-dense breast area using a validated computer-assisted method. Multivariable linear regression was used to estimate the association between endometriosis and mammographic density among pre- and postmenopausal women separately.
  
  
  
  Among premenopausal women, average percent mammographic density was 43.1 % among women with endometriosis (n = 91) and 40.5 % among women without endometriosis (n = 1,150). Endometriosis was not associated significantly with mammographic density among premenopausal (% difference = 2.00 percentage points 95 % CI -1.33, 5.33) or among postmenopausal women (% difference = -0.89 percentage points 95 % CI -5.10, 3.33). Among premenopausal women, there was heterogeneity by BMI at age 18 (p value = 0.003), with a suggested association among those who were lean at age 18 (BMI < 20.6 kg/m(2)) (% difference = 3.74 percentage points 95 % CI -0.29, 7.78).
  
  
  
  Endometriosis was not found to be associated with overall measurements of mammographic density.
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA, 02115, USA. lfarland@mail.harvard.edu.|Department of Obstetrics, Gynecology, and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA. lfarland@mail.harvard.edu.
authors.forename: Leslie V
authors.identifier: 0000-0001-7455-8531
authors.initials: LV
authors.lastname: Farland
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA, 02115, USA.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Rulla M
authors.initials: RM
authors.lastname: Tamimi
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA, 02115, USA.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: A Heather
authors.initials: AH
authors.lastname: Eliassen
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA, 02115, USA.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.|Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA, USA.
authors.forename: Donna
authors.initials: D
authors.lastname: Spiegelman
authors.affiliation: Slone Epidemiology Center, Boston University, Boston, MA, USA.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Bertrand
authors.affiliation: Department of Epidemiology, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Boston, MA, 02115, USA.|Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.|Department of Obstetrics, Gynecology, and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
authors.forename: Stacey A
authors.initials: SA
authors.lastname: Missmer
mesh_terms: D000328:Adult; D000071060:Breast Density; D001943:Breast Neoplasms / Q000453:epidemiology / Q000473:pathology; D003430:Cross-Sectional Studies; D004715:Endometriosis / Q000453:epidemiology* / Q000473:pathology; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods; D008875:Middle Aged; D017698:Postmenopause; D017697:Premenopause; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology
keywords: Breast cancer; Breast density; Endometriosis; Epidemiology; Mammographic density