Table 1. Characteristics of breast cancer cases and health controls.
| Characteristics | Controls (n = 1256)(%) |
Cases (n = 1156)(%) |
P value |
|---|---|---|---|
| Age (year)(mean ± SD) | 47.4±10.8 | 46.7±10.4 | 0.118 |
| Education level | 1.96×10−36 | ||
| Uneducated or primary school | 499 (39.7) | 756 (65.4) | |
| High school or more | 757 (60.3) | 400 (34.6) | |
| BMI (kg/m2)(mean ± SD) | 23.0±3.0 | 22.6±2.6 | 4.60×10−5 |
| Age at first live birth (year)(mean ± SD) | 23.5±5.8 | 23.8±6.3 | 0.255 |
| Parity | 3.88×10−12 | ||
| 0-1 | 534 (42.5) | 655 (56.7) | |
| ≥2 | 722 (57.5) | 501 (43.3) | |
| Breast feeding period (year)(mean ± SD) | 17.6±17.9 | 15.7±13.3 | 0.005 |
| Breast feeding period (month) | 2.3×10−6 | ||
| <6 | 294 (23.4) | 182 (15.7) | |
| ≥6 | 962 (76.6) | 974 (84.3) | |
| Age at menarche (year)(mean ± SD)a | 15.4±1.7 | 15.1±1.7 | 5.06×10−4 |
| Age at menopausal (year)(mean ± SD) | 49.9±3.6 | 49.8±3.8 | 0.677 |
| Natural menstrual period (year)(mean ± SD) | 29.0±7.2 | 29.1±7.1 | 0.82 |
| Menopausal status | 0.004 | ||
| Premenopausal | 806 (64.2) | 755 (65.3) | |
| Postmenopausal | 426 (33.9) | 396 (34.3) | |
| Unnatural menopausal b | 24 (1.9) | 5 (0.4) | |
| Prior hormone replacement therapy | 4.66×10−3 | ||
| Yes | 28 (2.3) | 56 (4.8) | |
| No | 1228 (97.7) | 1100 (95.2) | |
| Previous benign breast disease | 0.044 | ||
| Yes | 30 (2.4) | 44 (3.8) | |
| No | 1226 (97.6) | 1112 (96.2) | |
| Family history of breast cancer | 7.77×10−16 | ||
| Yes | 12 (0.96) | 86 (7.44) | |
| No | 1244 (99.04) | 1070 (92.56) | |
| ER status | |||
| Positive | 778 (67.3) | ||
| Negative | 378 (32.7) | ||
| PR status | |||
| Positive | 709 (61.3) | ||
| Negative | 447 (38.7) | ||
| HER-2 status | |||
| Positive | 315 (27.2) | ||
| Negative | 841 (72.8) |
a
Postmenopausal women only.
b
Unnatural menopausal includes hysterectomy operation and other status.