Table 2

Rate ratios (RR) of breast cancer incidence according to recent body mass index (BMI) in 1992 stratified by hormone replacement therapy (HRT) use in 1992 in the Cancer Prevention Study-II Nutrition Cohort, 1992–1999

BMI 1992 (kg/m2)P
<22.022.0 to <25.025.0 to <27.027.0 to <3030.0 to <35.0≥35.0
Non-HRT users
 No. cases18730418223320472
 Age standardized rate402.5404.8412.7520.0623.5571.7
 Age-adjusted RRa1.001.031.051.291.561.44
 95% CI0.86–1.230.85–1.281.07–1.571.28–1.901.10–1.89
 Multivariate RRb1.001.061.111.411.741.61<0.0001
 95% CI0.88–1.270.91–1.361.16–1.711.42–2.131.22–2.12
 Multivariate RRc1.001.001.001.221.351.080.11
 95% CI0.83–1.220.80–1.260.97–1.541.04–1.760.75–1.55
Current HRT users
 No. cases2232531021015122
 Age standardized rate697.6587.6472.3577.9456.8621.1
 Age-adjusted RRa1.000.850.690.780.640.96
 95% CI0.71–1.020.55–0.870.62–0.990.47–0.870.62–1.49
 Multivariate RRb1.000.890.740.860.721.090.12
 95% CI0.74–1.060.59–0.940.68–1.090.53–0.980.70–1.69
 Multivariate RRc1.000.840.670.740.560.730.002
 95% CI0.69–1.010.52–0.870.56–0.970.40–0.800.45–1.21
  • a RR adjusted for age at interview.

  • b RR adjusted for age at interview, age at menarche, age at menopause, number of live births, age at first live birth, oral contraceptive use, family history of breast cancer, history of breast cysts, history of mammography, height, education, physical activity, alcohol use, and race.

  • c RR adjusted for total adult weight gain (age 18 years to 1992) in addition to all covariates listed above.