Table 2.

RR estimates and 95% CI for the association between OC use and risk of mortality in the Women's CARE Study

All-cause deaths (N = 1,064)Breast cancer deaths (N = 828)
Baseline variableNo.RR (95% CI)No.RR (95% CI)
OC use status
 Never2551.001721.00
 Ever8091.01 (0.86–1.19)6561.03 (0.85–1.25)
 Former7671.01 (0.86–1.19)6161.03 (0.85–1.24)
 Current410.89 (0.62–1.28)390.95 (0.65–1.40)
OC use duration, y
 <11870.94 (0.77–1.15)1420.92 (0.73–1.17)
 1–<52951.17 (0.97–1.41)2301.15 (0.93–1.43)
 5–<101800.97 (0.78–1.19)1541.02 (0.80–1.29)
 ≥101470.93 (0.74–1.16)1301.00 (0.78–1.28)
Ptrend0.520.35
Age at first OC use, y
 <203241.01 (0.82–1.24)2831.06 (0.84–1.35)
 20–242640.97 (0.80–1.18)2201.01 (0.81–1.27)
 25–291361.03 (0.83–1.28)920.93 (0.71–1.22)
 ≥30841.06 (0.82–1.36)601.09 (0.81–1.47)
Years between last OC use and breast cancer diagnosis
 ≥252361.11 (0.92–1.34)1751.12 (0.90–1.41)
 20–241911.01 (0.82–1.23)1450.97 (0.77–1.24)
 10 to <202500.94 (0.76–1.15)2161.00 (0.80–1.27)
 <101310.82 (0.64–1.06)1190.87 (0.65–1.15)
Years between menarche and first OC use
 <94081.01 (0.83–1.23)3551.06 (0.85–1.33)
 9 to <152530.95 (0.79–1.15)1980.97 (0.77–1.21)
 ≥151471.08 (0.88–1.33)1021.05 (0.82–1.35)
Years of OC use before FFTP
 1st OC use after FFTP3961.01 (0.86–1.20)3141.05 (0.86–1.29)
 No FFTP1251.06 (0.84–1.35)890.90 (0.68–1.20)
 <3610.89 (0.66–1.21)510.89 (0.63–1.25)
 3 to <6981.09 (0.84–1.41)881.15 (0.86–1.52)
 ≥61250.94 (0.74–1.21)1100.96 (0.73–1.27)
Calendar year of first OC use
 <19725441.05 (0.89–1.24)4211.07 (0.88–1.31)
 ≥19732640.87 (0.69–1.09)2340.87 (0.67–1.13)

NOTE: Total number of deaths may vary due to missing values in corresponding variables. All models use age (in days) as the time metric and stratify on age (in years) at breast cancer diagnosis. Covariates included in the models are study site, race, ER status, tumor stage, education level, smoking status, alcohol consumption, number of comorbidities, number of mammograms within the 5 years before breast cancer diagnosis, BMI 5 years before cancer diagnosis, and age at menarche.

Abbreviations: CARE, Contraceptive and Reproductive Experiences; FFTP, first full-term pregnancy; OC, oral contraceptives.