| White women | African-American women | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Controls | Triple-negative | Luminal A-like | Controls | Triple-negative | Luminal A-like | |||||
N | N | OR (95% CI) | N | OR (95% CI) | N | N | OR (95% CI) | N | OR (95% CI) | |
Younger (20–44 years)a | ||||||||||
 Duration of breastfeeding, months | ||||||||||
  Never | 85 | 27 | 1.00 | 57 | 1.00 | 119 | 37 | 1.00 | 43 | 1.00 |
  Ever | 383 | 105 | 0.85 (0.49–1.49) | 218 | 0.71 (0.46–1.11) | 148 | 37 | 0.43 (0.22–0.83) | 48 | 0.58 (0.32–1.06) |
   <6 | 136 | 43 | 0.94 (0.52–1.72) | 72 | 0.70 (0.43–1.14) | 73 | 26 | 0.67 (0.33–1.36) | 25 | 0.64 (0.32–1.26) |
   ≥6 | 247 | 62 | 0.76 (0.41–1.41) | 146 | 0.73 (0.45–1.18) | 75 | 11 | 0.18 (0.07–0.46) | 23 | 0.50 (0.24–1.06) |
  Trend P value |  |  | 0.34 |  | 0.28 |  |  | 0.0004 |  | 0.07 |
   P value for homogeneity of trends | 0.93 |  |  |  |  | 0.09 |  | |||
Older (45–64 years)b | ||||||||||
 Duration of breastfeeding, months | ||||||||||
  Never | 283 | 39 | 1.00 | 171 | 1.00 | 261 | 63 | 1.00 | 96 | 1.00 |
  Ever | 462 | 74 | 1.06 (0.65–1.72) | 374 | 0.83 (0.63–1.10) | 249 | 48 | 0.74 (0.47–1.17) | 92 | 0.90 (0.62–1.30) |
    < 6 | 207 | 41 | 1.30 (0.78–2.19) | 158 | 0.91 (0.67–1.25) | 125 | 24 | 0.69 (0.39–1.21) | 48 | 0.94 (0.60–1.46) |
    ≥ 6 | 255 | 33 | 0.75 (0.41–1.38) | 216 | 0.73 (0.53–1.02) | 124 | 24 | 0.81 (0.46–1.43) | 44 | 0.85 (0.54–1.35) |
  Trend P value |  |  | 0.41 |  | 0.07 |  |  | 0.35 |  | 0.49 |
   P value for homogeneity of trends | 0.85 |  |  |  |  | 0.72 |  |