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Table 1 Mean ± SE for continuous baseline covariates, and number (%) for categorical baseline covariates for breast cancer cases and controls occurring during the intervention phases of the Women’s Health Initiative CEE + MPA and CEE trials

From: Sex hormone associations with breast cancer risk and the mediation of randomized trial postmenopausal hormone therapy effects

  CEE + MPA trial CEE trial
  Cases Controls P-value* Cases Controls P-value*
N 348 348   235 235  
Age 64.32 ± 6.85 64.33 ± 6.82 0.98 64.5 ± 7.11 64.49 ± 7.06 0.97
BMI 29.33 ± 5.56 28.46 ± 5.69 0.04 31.46 ± 5.98 29.32 ± 5.70 <0.01
Gail model five-year risk score (%) 1.85 ± 0.89 1.72 ± 0.84 0.05 1.84 ± 1.65 1.36 ± 0.90 0.08
Race (%)    0.99    0.98
White 305 (87.6) 305 (87.6)   184 (78.3) 184 (78.3)
Black 21 (6.0) 21 (6.0)   36 (15.3) 35 (14.9)
Other 22 (6.3) 22 (6.3)   15 (6.4) 16 (6.8)
Smoking (%)    0.11    0.72
Never 158 (46.1) 186 (54.1)   129 (55.1) 126 (53.6)
Past 155 (45.2) 131 (38.1)   87 (37.2) 86 (36.6)
Current 30 (8.7) 27 (7.8)   18 (7.7) 23 (9.8)
Family history of breast cancer (%)    0.006    0.23
Yes 79 (24.0) 50 (15.2) 52 (23.5) 42 (18.5)
No 250 (76.0) 280 (84.8)   169 (76.5) 185 (81.5)  
  1. *P-values are significance levels from Student’s t-test and chi-square tests of no difference between cases and controls for continuous and categorical variables.
  2. Matching variables in control selection. BMI, body mass index; CEE, conjugated equine estrogens; MPA, medroxyprogesterone acetate.