| Controls | Triple-negative | Luminal A-like | Luminal B-like | HER2-enriched | ||||
---|---|---|---|---|---|---|---|---|---|
N | N | OR (95% CI) | N | OR (95% CI) | N | OR (95% CI) | N | OR (95% CI) | |
All women | |||||||||
 Age at menarche, years | |||||||||
   ≤ 12 | 1292 | 289 | 1.00 | 820 | 1.00 | 186 | 1.00 | 110 | 1.00 |
  13 | 634 | 158 | 1.13 (0.90–1.41) | 419 | 0.98 (0.84–1.16) | 99 | 1.06 (0.81–1.40) | 66 | 1.22 (0.88–1.69) |
   ≥ 14 | 522 | 107 | 0.89 (0.69–1.14) | 278 | 0.77 (0.64–0.92) | 75 | 0.92 (0.68–1.24) | 51 | 1.07 (0.75–1.53) |
  Trend P value | 0.55 |  | 0.009 |  | 0.70 |  | 0.56 | ||
   P value for homogeneity of trends | 0.19 |  |  |  |  |  |  | ||
 Number of completed pregnancies | |||||||||
  Never pregnant | 250 | 68 | 1.00 | 224 | 1.00 | 56 | 1.00 | 31 | 1.00 |
  Any completed pregnancies | 1990 | 431 | 0.91 (0.67–1.24) | 1104 | 0.79 (0.64–0.98) | 263 | 0.82 (0.58–1.15) | 176 | 0.78 (0.50–1.20) |
  1 | 399 | 98 | 0.95 (0.66–1.36) | 277 | 0.92 (0.71–1.19) | 84 | 1.17 (0.79–1.74) | 50 | 1.02 (0.62–1.67) |
  2 | 709 | 168 | 0.98 (0.70–1.37) | 438 | 0.81 (0.64–1.02) | 109 | 0.88 (0.61–1.29) | 59 | 0.69 (0.42–1.11) |
  ≥3 | 882 | 165 | 0.84 (0.60–1.19) | 389 | 0.64 (0.50–0.81) | 70 | 0.53 (0.35–0.80) | 67 | 0.65 (0.40–1.05) |
  Trend P value |  |  | 0.26 |  | <0.0001 |  | <0.0001 |  | 0.02 |
   P value for homogeneity of trends | 0.09 |  |  |  |  |  |  | ||
Only non-completed pregnancy | 208 | 55 | 0.91 (0.60–1.38) | 189 | 1.02 (0.76–1.35) | 41 | 0.88 (0.55–1.39) | 20 | 0.69 (0.38–1.26) |
Parous women onlya,b | |||||||||
 Age at first completed pregnancy, years | |||||||||
  ≤20 | 799 | 165 | 1.00 | 297 | 1.00 | 69 | 1.00 | 62 | 1.00 |
  21–24 | 510 | 107 | 1.03 (0.78–1.38) | 274 | 1.22 (0.98–1.52) | 63 | 1.18 (0.80–1.73) | 43 | 1.05 (0.68–1.62) |
  25–29 | 348 | 85 | 1.08 (0.77–1.52) | 275 | 1.64 (1.28–2.10) | 56 | 1.22 (0.78–1.89) | 33 | 1.10 (0.66–1.85) |
  ≥30 | 333 | 73 | 0.80 (0.54–1.20) | 256 | 1.17 (0.88–1.55) | 75 | 1.09 (0.68–1.74) | 38 | 0.96 (0.55–1.70) |
  Trend P value |  |  | 0.50 |  | 0.05 |  | 0.57 |  | 0.95 |
   P value for homogeneity of trends | 0.24 |  |  |  |  |  |  | ||
 Duration of breastfeeding, months | |||||||||
  Never | 748 | 166 | 1.00 | 370 | 1.00 | 81 | 1.00 | 60 | 1.00 |
  Ever | 1242 | 264 | 0.80 (0.63–1.02) | 732 | 0.78 (0.65–0.94) | 182 | 0.89 (0.65–1.23) | 116 | 0.91 (0.63–1.32) |
    < 6 | 541 | 134 | 0.96 (0.74–1.26) | 303 | 0.83 (0.68–1.02) | 82 | 0.99 (0.70–1.41) | 35 | 0.68 (0.43–1.07) |
   6–11 | 263 | 40 | 0.55 (0.37–0.82) | 165 | 0.76 (0.59–0.99) | 35 | 0.70 (0.44–1.12) | 33 | 1.28 (0.78–2.09) |
    ≥ 12 | 438 | 90 | 0.69 (0.50–0.96) | 264 | 0.71 (0.56–0.90) | 65 | 0.85 (0.56–1.30) | 48 | 1.10 (0.69–1.75) |
  Trend P value |  |  | 0.006 |  | 0.004 |  | 0.28 |  | 0.36 |
   P value for homogeneity of trends | 0.08 |  |  |  |  |  |  |