Menstrual and reproductive factors in relation to mammographic density: The Study of Women's Health Across the Nation (SWAN)

Lesley M. Butler, Ellen B Gold, Gail A. Greendale, Carolyn J. Crandall, Francesmary Modugno, Nina Oestreicher, Charles P. Quesenberry, Laurel A. Habel

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


Menstrual and reproductive factors may increase breast cancer risk through a pathway that includes increased mammographic density. We assessed whether known or suspected menstrual and reproductive breast cancer risk factors were cross-sectionally associated with mammographic density, by measuring area of radiographic density and total breast area on mammograms from 801 participants in the Study of Women's Health Across the Nation (SWAN), a multi-ethnic cohort of pre- and early perimenopausal women. From multivariable linear regression, the following menstrual or reproductive factors were independently associated with percent mammographic density (area of dense breast/breast area): older age at menarche (β = 10.3, P < 0.01, for >13 vs. <12 years), premenstrual cravings and bloating (β = -3.36, P = 0.02), younger age at first full-term birth (β = -8.12, P < 0.01 for ≤23 years versus no births), greater number of births (β = -6.80, P < 0.01 for ≥3 births versus no births), and premenopausal status (β = 3.78, P < 0.01 versus early perimenopausal). Only number of births remained associated with percent density after adjustment for age, race/ethnicity, study site, body mass index (BMI), and smoking. In addition, stratified analyses revealed that the association with number of births was confined to women within the lowest BMI tertile (β = -12.2, P < 0.01 for ≥3 births versus no births). Our data support a mechanism for parity and breast cancer that involves mammographic density among pre- and early perimenopausal women that may be modified by body size.

Original languageEnglish (US)
Pages (from-to)165-174
Number of pages10
JournalBreast Cancer Research and Treatment
Issue number1
StatePublished - Nov 2008


  • Age at first birth
  • Body size
  • Breast cancer risk factor
  • Mammographic density
  • Menarche
  • Menstrual factors
  • Parity
  • Perimenopause
  • Premenopausal
  • Reproductive factors

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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