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Table 3 Case-only odds ratios and 95% confidence intervals from logistic regression modelsa of associations between breast cancer tumor subtypes and demographic, reproductive, and lifestyle risk factors, combined LACE and Pathways Studies (n = 2544)

From: Epidemiology of breast cancer subtypes in two prospective cohort studies of breast cancer survivors

  Luminal A (comparison) Luminal Ba
  n N OR 95% CI
Age at diagnosis (years)     
   ≥ 65 (Ref) 637 82 Ref ---
   50 to 64 871 124 1.09 0.81, 1.47
   < 50 355 88 1.83 1.32, 2.55
   Test for trend     P = 0.0001
Race/ethnicity     
   White (Ref) 1464 215 Ref ---
   African American 92 14 0.97 0.54, 1.74
   Hispanic 135 28 1.32 0.85, 2.04
   Asian 135 30 1.38 0.90, 2.12
   Other 37 7 1.29 0.56, 2.94
Menopausal status     ---
   Postmenopausal (Ref) 1283 173 Ref  
   Premenopausal 406 95 1.32 0.87, 2.00
Family history     
   No (Ref) 1453 245 Ref ---
   Yes 410 49 0.74 0.53, 1.02
Age at first full-term pregnancy (years)     
   Nulliparous (Ref) 335 51 Ref ---
   < 26 959 158 1.25 0.88, 1.78
   ≥ 26 567 85 1.04 0.72, 1.52
Parity     
   Nulliparous (Ref) 335 51 Ref ---
   1 to 2 children 837 150 1.24 0.88, 1.76
   ≥ 3 children 691 93 1.03 0.70, 1.50
Lifetime duration of breastfeeding     
   Never (Ref) 871 135 Ref ---
   0 to 3 months 255 50 1.31 0.92, 1.88
   ≥ 4 months 711 100 0.86 0.65, 1.14
Parity among never breastfedb     
   Nulliparous (Ref) 321 50 Ref ---
   1 to 2 children 326 59 1.38 (0.89, 2.13)
   ≥ 3 children 224 26 1.01 (0.58, 1.76)
Parity among 0 to 3 months breastfedb     
   1 to 2 children (Ref) 144 33 Ref ---
   ≥ 3 children 108 17 0.90 (0.45, 1.77)
Parity among ≥ 4 months breastfedb     
   1 to 2 children (Ref) 358 56 Ref ---
   ≥ 3 children 352 44 0.84 (0.54, 1.32)
Alcohol use     
   Never (Ref) 709 131 Ref ---
   Ever 880 119 0.74 0.56, 0.98
Smoking history     
   Never (Ref) 921 163 Ref ---
   ≤ 10 251 39 0.86 0.59, 1.27
   11 to 19 147 22 0.93 0.57, 1.51
   ≥ 20 531 68 0.80 0.59, 1.09
Hormone replacement therapy (postmenopausal only)     
   Never (Ref) 314 55 Ref ---
   Ever 943 114 0.66 0.46, 0.94
Oral contraceptive use     
   Never (Ref) 647 110 Ref ---
   Ever 1160 172 0.73 0.55, 0.96
BMI (kg/m2)c     
   < 25 (Ref) 785 134 Ref ---
   25 to 29 563 79 0.92 0.67, 1.24
   ≥ 30 500 77 1.03 0.75, 1.41
BMI (kg/m2) among premenopausalb     
   < 25 (Ref) 223 50 Ref ---
   25 to 29 99 21 1.11 0.62, 2.00
   ≥ 30 81 24 1.68 0.92, 3.07
BMI (kg/m2) among postmenopausalb     
   < 25 (Ref) 480 67 Ref ---
   25 to 29 422 52 0.90 0.61, 1.33
   ≥ 30 372 50 0.99 0.66, 1.47
  1. a Adjusted for age at diagnosis, race/ethnicity, and Pathways/LACE study origin except in models with age at diagnosis or race/ethnicity as main predictors.
  2. b P for interaction not statistically significant (P > 0.05) in any tumor subtype model.
  3. c BMI = body mass index one year pre-diagnosis (LACE) and around diagnosis (Pathways).
  4. CI = confidence interval; OR = odds ratio.