Table 1. Characteristics of breast cancer cases and controls.
| Characteristic | Cases, n (%) | Controls, n (%) | P value |
| Age | |||
| ≤40 | 210 (25.0) | 226 (26.2) | |
| 41∼59 | 494 (58.9) | 491 (56.9) | |
| 60∼ | 135 (16.1) | 146 (16.9) | 0.709 |
| Mean ± SD | 48.97±11.57 | 49.23±11.76 | 0.654b |
| Education | |||
| Junior middle school or below | 389 (46.4) | 315 (36.5) | |
| Senior middle school | 216 (25.7) | 326 (37.8) | |
| College or above | 174 (20.7) | 188 (21.8) | <0.001 |
| Unknown | 60 (7.2) | 34 (3.9) | |
| Marital status | |||
| Never married | 41 (4.9) | 33 (3.8) | |
| Married/living as married | 711 (84.7) | 717 (83.1) | |
| Separated/widow | 46 (5.5) | 63 (7.3) | 0.182 |
| Unknown | 41 (4.9) | 50 (5.8) | |
| Body mass index (kg/m2) | |||
| <22 | 349 (41.6) | 338 (39.2) | |
| 22∼24 | 240 (28.6) | 273 (31.6) | |
| ≥25 | 206 (24.6) | 196 (22.7) | 0.293 |
| Unknown | 44 (5.2) | 56 (6.5) | |
| Age at menarche (years) | |||
| ≤12 | 109 (13.0) | (15.5) | |
| >12 | 682 (81.3) | 689 (79.8) | 0.160 |
| Unknown | 48 (5.7) | 40 (4.6) | |
| Menopausal status | |||
| Premenopausal | 479 (57.1) | 402 (46.6) | |
| Postmenopausal | 338 (40.3) | 430 (49.8) | <0.001 |
| Unknown | 22 (2.6) | 31 (3.6) | |
| Age at menopause (years)a | |||
| ≤45 | 72 (21.3) | 72 (16.7) | |
| 46∼50 | (38.5) | 182 (42.3) | |
| >50 | 99 (29.3) | 155 (36.1) | 0.096 |
| Unknown | 37 (11.0) | 21 (4.9) | |
| Parity | |||
| 0 | 73 (8.7) | 59 (6.8) | |
| ≥1 | 732 (87.3) | 772 (89.5) | |
| Unknown | 34 (4.1) | 32 (3.7) | 0.144 |
| Family history of breast cancer | |||
| Absent | 780 (93.0) | 800 (92.7) | |
| Present | 25 (3.0) | 28 (3.2) | 0.753 |
| Unknown | 34 (4.1) | 35 (4.1) |
a
Postmenopausal women only.
b
Student's t-test.
P values in bold indicate statistical significance.