Table 3.

RR estimates and 95% CI for the association between OC use and mortality in the CTS

All-cause deaths (N = 523)Breast cancer deaths (N = 261)
Baseline variableNo.RR (95% CI)No.RR (95% CI)
OC use status
 Never2871.001061.00
 Evera2360.84 (0.67–1.05)1550.89 (0.64–1.23)
OC use duration, y
 <1340.77 (0.52–1.14)190.83 (0.49–1.43)
 1 to <5800.85 (0.63–1.16)540.88 (0.59–1.33)
 5 to <10670.99 (0.72–1.36)440.97 (0.63–1.50)
 ≥10450.67 (0.47–0.96)320.75 (0.48–1.18)
Ptrend0.220.72
Age at first OC use, y
 <20260.76 (0.46–1.26)230.87 (0.49–1.55)
 20–24780.66 (0.46–0.95)580.65 (0.42–1.02)
 25–29510.87 (0.61–1.24)350.99 (0.63–1.57)
 ≥30740.90 (0.68–1.18)330.94 (0.61–1.45)
Years between last OC use and breast cancer diagnosis
 ≥251410.84 (0.65–1.07)830.85 (0.59–1.21)
 20–24380.84 (0.57–1.24)300.98 (0.60–1.58)
 10 to <20371.00 (0.66–1.53)270.99 (0.58–1.67)
 <1080.47 (0.18–1.22)70.44 (0.15–1.31)
Years between menarche and first OC use
 <9490.71 (0.47–1.08)410.82 (0.50–1.34)
 9 to <15820.76 (0.55–1.06)600.79 (0.52–1.21)
 ≥15970.90 (0.69–1.16)470.94 (0.64–1.37)
Years of OC use before FFTP
 First OC after FFTP890.79 (0.61–1.03)490.90 (0.62–1.32)
 No FFTP591.09 (0.77–1.53)330.82 (0.51–1.32)
 <3100.62 (0.31–1.26)50.52 (0.20–1.34)
 3 to <6290.84 (0.53–1.32)250.97 (0.57–1.65)
 ≥6440.82 (0.54–1.24)380.84 (0.51–1.38)
Calendar year of first OC use
 <19722070.85 (0.68–1.08)1330.90 (0.65–1.26)
 ≥1973220.57 (0.30–1.06)160.45 (0.20–1.03)

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 by age (in years) at breast cancer diagnosis. Covariates included in the models are race, ER status, tumor stage, socioeconomic status, smoking status, alcohol consumption, number of comorbidities, years since last mammogram, BMI at cohort entry and age at menarche.

Abbreviations: CTS, California Teachers Study; FFTP, first full-term pregnancy; OC, oral contraceptives.

  • aTwo deaths occurred among current OC users.