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Table 2 Adjusted odds ratios (OR) and 95% confidence intervals (CI) for association between breast cancer subtypes associated and reproductive factors

From: Parity, hormones and breast cancer subtypes - results from a large nested case-control study in a national screening program

  Luminal A-like Luminal B-like HER2-negative Luminal B-like HER2-positive HER2-positive Triple-negative
ER+ PR+ HER2- ER+ PR- HER2- ER+ PR+/PR- HER2+ ER- PR- HER2+ ER- PR- HER2-
Controls (n) Cases (n) OR* 95% CI Controls (n) Cases (n) OR 95% CI Controls (n) Cases (n) OR 95% CI Controls (n) Cases (n) OR 95% CI Controls (n) Cases (n) OR 95% CI
Age at first birth (years)
 13–20 3951 746 1 Reference 1001 169 1 Reference 553 96 1 Reference 279 54 1 Reference 495 95 1 Reference
 21–22 2277 460 1.04 (0.91, 1.18) 620 120 1.22 (0.93, 1.59) 305 51 0.97 (0.65, 1.43) 170 32 0.97 (0.58, 1.62) 326 65 1.10 (0.77, 1.57)
 23–25 3152 591 0.97 (0.85, 1.10) 759 157 1.29 (1.00, 1.67) 437 92 1.27 (0.90, 1.78) 222 36 0.75 (0.46, 1.22) 393 86 1.27 (0.89, 1.81)
 26–30 2473 547 1.12 (0.98, 1.28) 647 141 1.30 (0.99, 1.71) 343 62 1.21 (0.82, 1.78) 216 41 0.97 (0.59, 1.58) 318 63 1.16 (0.79, 1.70)
 31–50 937 238 1.19 (0.99, 1.43) 223 60 1.60 (1.10, 2.32) 127 32 1.64 (0.98, 2.74) 63 23 1.67 (0.89, 3.12) 120 29 1.47 (0.88, 2.47)
 Never (nulliparous) 1199 328 1.76 (1.44, 2.15) 303 89 1.96 (1.31, 2.91) 164 49 2.74 (1.57, 4.78) 84 27 1.82 (0.85, 3.88) 144 34 1.58 (0.89, 2.81)
p-trenda    0.07     0.01     0.06     0.49     0.16  
p-heterogeneity#        0.19     0.19     0.31     0.68  
Number of pregnancies lasting 6+ months
 0 1199 328 1 Reference 303 89 1 Reference 164 49 1 Reference 84 27 1 Reference 144 34 1 Reference
 1 1596 397 0.91 (0.77, 1.08) 426 84 0.68 (0.48, 0.96) 229 42 0.53 (0.33, 0.86) 128 20 0.50 (0.26, 0.96) 224 41 0.70 (0.42, 1.16)
 2 6266 1302 0.76 (0.66, 0.88) 1602 323 0.68 (0.52, 0.90) 842 185 0.71 (0.49, 1.04) 426 97 0.78 (0.47, 1.29) 813 158 0.77 (0.50, 1.18)
 3 3883 721 0.66 (0.57, 0.77) 950 197 0.69 (0.52, 0.93) 528 89 0.54 (0.36, 0.82) 319 60 0.61 (0.36, 1.03) 477 117 0.98 (0.63, 1.53)
 >4 1518 237 0.56 (0.46, 0.68) 383 65 0.58 (0.40, 0.84) 225 31 0.42 (0.25, 0.70) 98 19 0.60 (0.31, 1.19) 196 36 0.70 (0.41, 1.21)
p-trend    <0.0001     0.02     0.002     0.19     0.88  
p-heterogeneity        0.31     0.42     0.34     0.03  
Parous women only
 Duration breastfeeding (months)
  No breastfeeding 997 204 1 Reference 260 51 1 Reference 146 33 1 Reference 78 10 1 Reference 135 24 1 Reference
  1–6 3145 607 0.95 (0.79, 1.15) 831 170 1.01 (0.70, 1.45) 449 74 0.66 (0.40, 1.07) 243 37 1.42 (0.63, 3.18) 467 80 1.01 (0.60, 1.71)
  7 − 12 3108 663 1.09 (0.91, 1.31) 763 158 1.05 (0.73, 1.51) 427 98 0.83 (0.51, 1.33) 215 52 2.25 (1.02, 4.99) 359 95 1.65 (0.98, 2.78)
  13 − 20 2583 496 1.02 (0.83, 1.24) 654 130 0.98 (0.67, 1.44) 343 77 0.90 (0.54, 1.49) 156 48 2.51 (1.11, 5.68) 308 69 1.29 (0.74, 2.23)
  21 − 30 1700 319 1.03 (0.83, 1.28) 399 79 0.97 (0.64, 1.46) 240 37 0.60 (0.33, 1.10) 147 28 1.78 (0.74, 4.28) 222 44 1.18 (0.65, 2.15)
  >30 966 195 1.15 (0.89, 1.48) 250 48 1.03 (0.63, 1.69) 121 16 0.69 (0.33, 1.47) 70 13 1.82 (0.67, 4.97) 123 24 1.19 (0.58, 2.44)
   p-trend    0.22     0.90     0.63     0.12     0.52  
   p-heterogeneity        0.85     0.25     0.56     0.84  
 Menopausal status
  Premenopausal 1171 351 1 Reference 208 47 1 Reference 173 32 1 Reference 100 18 1 Reference 130 29 1 Reference
  Perimenopausal 1055 229 0.61 (0.50, 0.74) 225 50 0.95 (0.60, 1.51) 152 26 0.86 (0.47, 1.54) 79 20 1.41 (0.67, 2.94) 143 37 1.13 (0.64, 1.99)
  Postmenopausal 12000 2405 0.51 (0.43, 0.60) 3231 661 0.84 (0.58, 1.23) 1663 338 1.11 (0.69, 1.78) 876 185 1.21 (0.66, 2.23) 1581 320 0.82 (0.50, 1.33)
   p-trend    <0.0001     0.30     0.46     0.71     0.21  
   p-heterogeneity        <0.0001     0.01     0.001     0.003  
 Age at menopause (years)
  <47 2558 450 1 Reference 638 136 1 Reference 333 47 1 Reference 203 22 1 Reference 336 61 1 Reference
  47–49 2393 449 1.09 (0.94, 1.26) 637 128 0.98 (0.74, 1.29) 321 60 1.48 (0.96, 2.27) 180 39 2.05 (1.14, 3.70) 291 72 1.50 (1.01, 2.24)
  50–52 4571 870 1.11 (0.98, 1.26) 1162 241 0.98 (0.77, 1.24) 644 131 1.59 (1.09, 2.32) 324 76 2.21 (1.31, 3.75) 611 102 1.04 (0.72, 1.49)
  >52 3051 633 1.12 (0.97, 1.28) 840 164 0.95 (0.73, 1.24) 415 94 1.70 (1.13, 2.55) 202 48 2.36 (1.33, 4.21) 395 88 1.38 (0.94, 2.01)
  Never (premenopausal) 1171 351 2.34 (1.93, 2.85) 208 47 1.17 (0.76, 1.80) 173 32 1.50 (0.86, 2.61) 100 18 1.76 (0.81, 3.80) 130 29 1.55 (0.88, 2.72)
   p-trenda    0.12     0.72     0.01     0.004     0.38  
   p-heterogeneity        0.70     0.09     0.08     0.28  
  1. aThe category Never was not included in the analysis of p-trend. *p for trend and OR mutually adjusted for age (50–54, 55–59, 60–64, 65–70 years at screening), body mass index (BMI) (≤22, 23–25, 26–28, >28 at screening), education (no education/primary school, high school, bachelor or master’s degree), age at menarche (9–12, 13, 14, 15–18 years), number of pregnancies (0, 1, 2, 3, ≥4), menopausal status (premenopausal, perimenopausal, postmenopausal). # p for heterogeneity across subtypes was determined in a case − case model (see “Methods”). ER estrogen receptor, PR progesterone receptor, HER2 human epidermal growth factor receptor 2