Table 2 Age- and study site-stratified RR (95% CI) for breast cancer in China Kadoorie Biobank
| Â | Cases | Cases/PYs | RR (95% CI) |
|---|---|---|---|
(/100,000) | |||
Highest education | |||
 No formal school | 339 | 44.64 | 1.00 (reference) |
 Primary school | 570 | 60.18 | 1.17 (1.11 to 1.23) |
 Middle school | 653 | 84.82 | 1.37 (1.24 to 1.51) |
 High school | 505 | 124.5 | 1.60 (1.39 to 1.85) |
 College/university | 220 | 165.2 | 1.87 (1.54 to 2.27) |
BMI at age < 50 years, kg/m2 | |||
 < 18.5 | 21 | 98.83 | 1.00 (reference) |
 18.5–23.9 | 357 | 126.42 | 0.95 (0.84 to 1.07) |
 24.0–27.9 | 187 | 160.42 | 0.90 (0.71 to 1.14) |
 ≥28 | 43 | 135.81 | 0.85 (0.60 to 1.21) |
BMI at age ≥ 50 years, kg/m2 | |||
 < 18.5 | 36 | 41.07 | 1.00 (reference) |
 18.5–23.9 | 642 | 66.66 | 1.25 (1.17 to 1.33) |
 24.0–27.9 | 683 | 94.59 | 1.57 (1.38 to 1.78) |
 ≥28 | 318 | 118.27 | 1.96 (1.62 to 2.38) |
Height, cm | |||
 < 150.2 | 382 | 51.58 | 1.00 (reference) |
 150.2–154.1 | 504 | 66.66 | 1.13 (1.09 to 1.18) |
 154.2–158.1 | 596 | 78.54 | 1.28 (1.18 to 1.39) |
 ≥ 158.2 | 805 | 105.96 | 1.45 (1.28 to 1.65) |
No. of first-degree relatives diagnosed with overall cancer | |||
 0 | 1795 | 71.63 | 1.00 (reference) |
 1 | 402 | 90.71 | 1.10 (0.99 to 1.23) |
 ≥ 2 | 90 | 136.09 | 1.57 (1.27 to 1.95) |
No. of live birth | |||
 Nulliparous | 45 | 112.79 | 1.78 (1.29 to 2.45) |
 1 | 1067 | 101.84 | 1.66 (1.40 to 1.96) |
 2 | 719 | 74.19 | 1.41 (1.22 to 1.62) |
 ≥ 3 | 456 | 47.58 | 1.00 (reference) |
Age at menarche, years | |||
 < 12 | 187 | 114.7 | 1.52 (1.31 to 1.76) |
 13–14 | 748 | 88.12 | 1.32 (1.20 to 1.46) |
 15–16 | 837 | 74.27 | 1.15 (1.09 to 1.21) |
 ≥ 17 | 515 | 58.77 | 1.00 (reference) |