Table 3

RR of breast cancer according to timing of postmenopausal hormone use

Estrogen onlyEstrogen with progestin only
CasesControlsRRa (95% CI)CasesControlsRRa (95% CI)
Duration of use (yrs)
 All users
  <54024491.08 (0.92–1.27)1981931.36 (1.07–1.73)
  ≥56055781.36 (1.17–1.58)117931.58 (1.16–2.15)
  Continuous (per yr)b,c1.02 (1.01–1.03)1.04 (1.01–1.08)
P < 0.001P = 0.005
 Current users
  <51571921.07 (0.84–1.37)1631701.32 (1.02–1.70)
  ≥54434491.34 (1.12–1.59)107911.50 (1.09–2.06)
  Continuous (per yr)b1.02 (1.01–1.02)1.04 (1.01–1.07)
P = 0.002P = 0.01
Time since last use (yrs)
 Current user6006411.25 (1.08–1.45)2702611.39 (1.12–1.71)
  <584531.76 (1.21–2.56)31191.71 (0.92–3.18)
  5–954501.22 (0.80–1.87)
  10–191611621.12 (0.87–1.43)1462.38 (0.82–6.87)d
  ≥201071121.04 (0.77–1.40)
  Continuous (per yr)b0.99 (0.99–1.00)0.98 (0.97–0.99)
P < 0.001P < 0.001
  • a Relative to nonusers (3827 cases and 4132 controls). Logistic regression models conditional on age and state. RRs were adjusted for age at menopause, type of menopause, age at first full-term pregnancy, body mass index, family history of breast cancer, education, screening mammography history, recent alcohol consumption, history of benign breast disease, age at menarche, and recent physical activity. Women who used both unopposed estrogen and estrogen-progestin are excluded.

  • b Includes nonusers.

  • c In the test of the difference in RRs for the duration of estrogen-only versus estrogen-progestin use, χ2 = 2.64, 1 degrees of freedom, P = 0.10. Among users of estrogen with progestin added <10 days/month, RR, 1.05; 95% CI, 0.99–1.12, P = 0.1, 10–21 days/month, RR, 1.03, 95% CI, 0.98–1.09, P = 0.3; >21 days/month, RR, 1.05, 95% CI, 1.00–1.10, P = 0.05.

  • d Estimate for time since last use ≥5 years.