Risk factor | Subtype | ||||||
---|---|---|---|---|---|---|---|
A-like (comparison group) | B-like | HER2-enriched | Triple-negative | ||||
N | N | ORa (95% CI) | N | OR (95% CI) | N | OR (95% CI) | |
Ethnicity | |||||||
 Chinese | 567 | 435 | 1.00 (reference) | 180 | 1.00 (reference) | 275 | 1.00 (reference) |
 Malay | 204 | 263 | 1.50 (1.18, 1.90) | 104 | 1.54 (1.13, 2.11) | 155 | 1.51 (1.14, 1.98) |
 Native | 245 | 291 | 1.39 (1.10, 1.76) | 103 | 1.21 (0.88, 1.66) | 190 | 1.50 (1.15, 1.95) |
 P value |  |  | 0.001 |  | 0.10 |  | < 0.001 |
Menarche | |||||||
  ≤ 12 yrs | 344 | 326 | 1.00 (reference) | 118 | 1.00 (reference) | 190 | 1.00 (reference) |
 13 yrs | 318 | 340 | 1.14 (0.91, 1.43) | 148 | 1.31 (0.98, 1.77) | 201 | 1.15 (0.88, 1.49) |
 14 yrs | 163 | 167 | 1.04 (0.79, 1.38) | 60 | 1.02 (0.70, 1.48) | 111 | 1.18 (0.86, 1.61) |
  ≥ 15 yrs | 184 | 148 | 0.83 (0.63, 1.10) | 57 | 0.87 (0.59, 1.28) | 113 | 1.10 (0.80, 1.50) |
 P value |  |  | 0.43 |  | 0.51 |  | 0.31 |
Parity and BFb | |||||||
 Nulliparous | 242 | 224 | 1.00 (reference) | 77 | 1.00 (reference) | 128 | 1.00 (reference) |
 Parous and No BF | 133 | 103 | 1.26 (0.84, 1.90) | 31 | 1.07 (0.76, 1.52) | 64 | 1.25 (0.77, 2.00) |
 Parous and BF | 641 | 662 | 1.44 (1.05, 1.98) | 279 | 1.64 (1.06, 2.55) | 428 | 1.54 (1.07, 2.22) |
 P value |  |  | 0.17 |  | 0.005 |  | 0.12 |
Age at FFPc | |||||||
  < 21 yrs | 116 | 158 | 1.00 (reference) | 54 | 1.00 (reference) | 95 | 1.00 (reference) |
 21–24.9 yrs | 284 | 287 | 0.78 (0.57, 1.05) | 129 | 1.01 (0.67, 1.51) | 199 | 0.90 (0.64, 1.26) |
 25–30 yrs | 275 | 248 | 0.77 (0.57, 1.06) | 103 | 0.91 (0.60, 1.38) | 154 | 0.77 (0.54, 1.09) |
  > 30 yrs | 99 | 72 | 0.63 (0.42, 0.94) | 24 | 0.57 (0.32, 1.02) | 43 | 0.58 (0.36, 0.93) |
 P value |  |  | 0.35 |  | 0.06 |  | 0.38 |
Family history | |||||||
 No | 840 | 854 | 1.00 (reference) | 338 | 1.00 (reference) | 516 | 1.00 (reference) |
 Yes | 160 | 119 | 0.72 (0.55, 0.94) | 46 | 0.71 (0.49, 1.02) | 92 | 0.92 (0.69, 1.23) |
 P value |  |  | 0.02 |  | 0.05 |  | 0.62 |
BMI, kg/m2 | |||||||
 18.5–24.9 | 160 | 172 | 1.00 (reference) | 68 | 1.00 (reference) | 114 | 1.00 (reference) |
  < 18.5 | 373 | 336 | 0.89 (0.69, 1.17) | 163 | 1.07 (0.76, 1.51) | 240 | 0.96 (0.72, 1.29) |
 P value |  |  | 0.38 |  | 0.65 |  | 0.76 |
 25–29.9 | 317 | 301 | 0.86 (0.65, 1.12) | 104 | 0.74 (0.51, 1.06) | 177 | 0.75 (0.55, 1.02) |
 P value |  |  | 0.27 |  | 0.13 |  | 0.08 |
  ≥ 30 | 136 | 148 | 0.90 (0.65, 1.24) | 38 | 0.55 (0.34, 0.89) | 66 | 0.59 (0.40, 0.88) |
 P value |  |  | 0.62 |  | 0.02 |  | 0.01 |