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) | Â | Â | Â | Â |
   ≥ 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 | Â | Â | Â | Â |
   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 | Â | Â | Â | --- |
   Postmenopausal (Ref) | 1283 | 173 | Ref |  |
   Premenopausal | 406 | 95 | 1.32 | 0.87, 2.00 |
Family history | Â | Â | Â | Â |
   No (Ref) | 1453 | 245 | Ref | --- |
   Yes | 410 | 49 | 0.74 | 0.53, 1.02 |
Age at first full-term pregnancy (years) | Â | Â | Â | Â |
   Nulliparous (Ref) | 335 | 51 | Ref | --- |
   < 26 | 959 | 158 | 1.25 | 0.88, 1.78 |
   ≥ 26 | 567 | 85 | 1.04 | 0.72, 1.52 |
Parity | Â | Â | Â | Â |
   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 | Â | Â | Â | Â |
   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 | Â | Â | Â | Â |
   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 | Â | Â | Â | Â |
   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 | Â | Â | Â | Â |
   Never (Ref) | 709 | 131 | Ref | --- |
   Ever | 880 | 119 | 0.74 | 0.56, 0.98 |
Smoking history | Â | Â | Â | Â |
   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) | Â | Â | Â | Â |
   Never (Ref) | 314 | 55 | Ref | --- |
   Ever | 943 | 114 | 0.66 | 0.46, 0.94 |
Oral contraceptive use | Â | Â | Â | Â |
   Never (Ref) | 647 | 110 | Ref | --- |
   Ever | 1160 | 172 | 0.73 | 0.55, 0.96 |
BMI (kg/m2)c | Â | Â | Â | Â |
   < 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 | Â | Â | Â | Â |
   < 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 | Â | Â | Â | Â |
   < 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 |