title: High mammographic density in women of Ashkenazi Jewish descent.
abstract: BACKGROUND
  Percent mammographic density (PMD) adjusted for age and body mass index is one of the strongest risk factors for breast cancer and is known to be approximately 60% heritable. Here we report a finding of an association between genetic ancestry and adjusted PMD.
  
  
  METHODS
  We selected self-identified Caucasian women in the California Pacific Medical Center Research Institute Cohort whose screening mammograms placed them in the top or bottom quintiles of age-adjusted and body mass index-adjusted PMD. Our final dataset included 474 women with the highest adjusted PMD and 469 with the lowest genotyped on the Illumina 1 M platform. Principal component analysis (PCA) and identity-by-descent analyses allowed us to infer the women's genetic ancestry and correlate it with adjusted PMD.
  
  
  RESULTS
  Women of Ashkenazi Jewish ancestry, as defined by the first principal component of PCA and identity-by-descent analyses, represented approximately 15% of the sample. Ashkenazi Jewish ancestry, defined by the first principal component of PCA, was associated with higher adjusted PMD (P = 0.004). Using multivariate regression to adjust for epidemiologic factors associated with PMD, including age at parity and use of postmenopausal hormone therapy, did not attenuate the association.
  
  
  CONCLUSIONS
  Women of Ashkenazi Jewish ancestry, based on genetic analysis, are more likely to have high age-adjusted and body mass index-adjusted PMD. Ashkenazi Jews may have a unique set of genetic variants or environmental risk factors that increase mammographic density.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Caswell
authors.forename: Karla
authors.initials: K
authors.lastname: Kerlikowske
authors.forename: John A
authors.initials: JA
authors.lastname: Shepherd
authors.forename: Steven R
authors.initials: SR
authors.lastname: Cummings
authors.forename: Donglei
authors.initials: D
authors.lastname: Hu
authors.forename: Scott
authors.initials: S
authors.lastname: Huntsman
authors.forename: Elad
authors.initials: E
authors.lastname: Ziv
mesh_terms: D000328:Adult; D000368:Aged; D000071060:Breast Density; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002140:California; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007585:Jews / Q000235:genetics*; D042361:Mammary Glands, Human / Q000002:abnormalities* / Q000473:pathology; D008327:Mammography; D008875:Middle Aged; D011247:Pregnancy; D044465:White People