Hormone-related risk factors and postmenopausal breast cancer among nulliparous versus parous women: An aggregated study

Sara J. Schonfeld, Ruth M. Pfeiffer, James V. Lacey, Amy Berrington De González, Michele M. Doody, Robert T. Greenlee, Yikyung Park, Catherine Schairer, Arthur Schatzkin, Alice J. Sigurdson, Patricia Hartge, Kala Visvanathan

Research output: Contribution to journalArticlepeer-review

Abstract

Nulliparity is an established breast cancer risk factor, particularly when compared with parity at young ages. The authors aggregated data from 4 US prospective studies (1979-2006) including 32,641 nulliparous (1,612 breast cancers) and 204,270 parous (8,180 breast cancers) women to examine the hypothesis that nulliparity may increase susceptibility to established postmenopausal breast cancer risk factors. The aggregated hazard ratio for nulliparous versus all parous women = 1.27 (95% confidence interval: 1.21, 1.34), and that for nulliparous versus women <25 years of age at first birth = 1.38 (95% confidence interval: 1.30, 1.46). Among nulliparous women, the hazard ratios for current menopausal hormone therapy use (vs. never use), body mass index ≥30 kg/m2 (vs. <25 kg/m2), and weekly consumption of ≥7 alcoholic drinks (vs. none) ranged from 1.3 to 1.6. The hazard ratios did not differ by parity. In a model including all women, the joint association for each of these factors and nulliparity combined compared with first birth before age 25 years was an approximately 2-fold increased breast cancer risk. Although the baseline risk is higher for nulliparous women compared with parous women, these results suggest that the associations between hormone-related factors and breast cancer do not differ by parity.

Original languageEnglish (US)
Pages (from-to)509-517
Number of pages9
JournalAmerican journal of epidemiology
Volume173
Issue number5
DOIs
StatePublished - Mar 1 2011

Keywords

  • alcohol drinking
  • body mass index
  • breast neoplasms
  • hormone replacement therapy
  • parity
  • prospective studies
  • risk factors

ASJC Scopus subject areas

  • Epidemiology

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