title: Varying levels of family history of breast cancer in relation to mammographic breast density (United States).
abstract: OBJECTIVE
  We examined the relationship between breast cancer family history and mammographic breast density.
  
  
  METHODS
  Participants included 35,019 postmenopausal women aged >or=40 years enrolled in a population-based mammography screening program. We collected data on the number and type of 1st and 2nd degree female relatives with a history of breast cancer and their ages at diagnosis. We used the Breast Imaging Reporting and Data System breast density categories to identify women with fatty (1 = almost entirely fatty or 2 = scattered fibroglandular tissue) and dense (3 = heterogeneously dense or 4 = extremely dense) breasts. We used logistic regression to calculate odds ratios (OR) and 95% confidence intervals for dense (N = 18,111) compared to fatty breasts (N = 16,908).
  
  
  RESULTS
  The odds of having dense breasts were 17% greater for women with affected 1st degree relatives than women with no family history. The odds increased with more affected 1st degree relatives [>or=3 vs. none (OR = 1.46; 1.05-2.01)] and among women with >or=1 affected 1st degree relative diagnosed <50 years (OR = 1.22; 1.10-1.34).
  
  
  CONCLUSIONS
  Having a family history of breast cancer was more strongly associated with mammographic breast density when the affected relatives were more genetically similar. There may be common, yet undiscovered, genetic elements that affect breast cancer and mammographic breast density.
authors.affiliation: Institute for Public Health Genetics, University of Washington, Seattle, WA, USA.
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Crest
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Aiello
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Anderson
authors.forename: Diana S M
authors.initials: DS
authors.lastname: Buist
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000473:pathology; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology; D016001:Confidence Intervals; D005192:Family Health; D005260:Female; D006801:Humans; D008327:Mammography; D008403:Mass Screening / Q000379:methods; D008487:Medical History Taking; D008875:Middle Aged; D016017:Odds Ratio; D012042:Registries; D012307:Risk Factors