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. Author manuscript; available in PMC: 2013 Jul 1.
Published in final edited form as: Cancer Epidemiol Biomarkers Prev. 2012 May 7;21(7):1089–1096. doi: 10.1158/1055-9965.EPI-12-0201

Table 5.

Association between various reproductive, hormonal and surgical exposures and risk of postmenopausal breast cancer among women who underwent natural menopause.

Exposure Univariate OR (95%CI) P Multivariate OR (95%CI) P
Oophorectomy, ever/never 0.13 (0.02–0.54) 0.006 0.13 (0.03–0.57)1 0.007
Parity, per birth 0.97 (0.83–1.13) 0.70 0.97 (0.83–1.13)2 0.69
Breastfeeding, per month4 0.99 (0.97–1.01) 0.16
Oral contraceptive use, ever/never 0.77 (0.46–1.27) 0.30 0.89 (0.52–1.50)3 0.66
Age at menarche, per year4 0.91 (0.81–1.03) 0.14
1

Estimate adjusted for parity (per birth) and oral contraceptive use (ever/never).

2

Estimate adjusted for oophorectomy (ever/never) and oral contraceptive use (ever/never).

3

Estimate adjusted for oophorectomy (ever/never) and parity (per birth).

4

Two of the three cases that had an oophorectomy had missing data on breastfeeding and one case had missing data on age at menarche and thus were excluded from the multivariate model for these exposures.