Reproductive and menstrual factors and colorectal cancer incidence in the Women's Health Initiative Observational Study

Neil Murphy, Linzhi Xu, Alice Zervoudakis, Xiaonan Xue, Geoffrey Kabat, Thomas E. Rohan, Sylvia Wassertheil-Smoller, Mary Jo O'Sullivan, Cynthia Thomson, Catherine Messina, Howard D. Strickler, Marc J. Gunter

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Background:Reproductive and menstrual factors have been evaluated as surrogates for long-term hormonal exposures in several prospective studies of colorectal cancer, yet findings have been conflicting.Methods:The relation of reproductive and menstrual factors (self-reported via a reproductive history questionnaire) with incident colorectal cancer was investigated among women enrolled in the Women's Health Initiative Observational Study (WHI-OS), a longitudinal cohort of 93 676 postmenopausal women (aged 50-79 years at enrolment) in which 1149 incident cases of colorectal cancer occurred over a median follow-up of 11.9 years. Multivariable Cox proportional hazards models that included established colorectal cancer risk factors were constructed to examine the association of colorectal cancer incidence with reproductive and menstrual factors.Results:Having had two children (vs nulliparous: hazard ratio (HR)=0.80, 95% confidence interval (CI): 0.64-0.99) was inversely associated with colorectal cancer risk. Compared with never users, ever use of oral contraceptives was associated with lower colorectal cancer risk (HR=0.74, 95% CI: 0.63-0.86); however, no relationship was observed for duration of oral contraceptives use (4 years vs 1 year: HR=0.94, 95% CI: 0.67-1.32). None of the remaining reproductive and menstrual factors was associated with colorectal cancer incidence.Conclusions:Parity and prior use of oral contraceptives were associated with lower colorectal cancer risk in this cohort of postmenopausal women.

Original languageEnglish (US)
Pages (from-to)117-125
Number of pages9
JournalBritish Journal of Cancer
Volume116
Issue number1
DOIs
StatePublished - Jan 3 2017

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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    Murphy, N., Xu, L., Zervoudakis, A., Xue, X., Kabat, G., Rohan, T. E., Wassertheil-Smoller, S., O'Sullivan, M. J., Thomson, C., Messina, C., Strickler, H. D., & Gunter, M. J. (2017). Reproductive and menstrual factors and colorectal cancer incidence in the Women's Health Initiative Observational Study. British Journal of Cancer, 116(1), 117-125. https://doi.org/10.1038/bjc.2016.345