Table 1 Characteristics of breast cancer cases and controls
Variables | Cases n = 1003 (%) | Controls n = 1107 (%) | P |
|---|---|---|---|
Age (years) | Â | Â | 0.751 |
  ≤ 40 | 253 (25.2) | 273 (24.7) |  |
 41–60 | 568 (56.6) | 644 (58.2) |  |
  > 60 | 182 (18.1) | 190 (17.2) |  |
 Mean age (SD) | 49.64 (11.79) | 49.58 (11.50) |  |
Education |  |  |  < 0.001 |
 Junior middle school or below | 491 (49.0) | 415 (37.5) |  |
 Senior middle school | 262 (26.1) | 410 (37.0) |  |
 College or above | 228 (22.7) | 276 (24.9) |  |
 Unknown | 22 (2.2) | 6 (0.5) |  |
Marital status | Â | Â | 0.750 |
 Never married | 31 (3.1) | 41 (3.7) |  |
 Married/cohabiting | 889 (88.6) | 979 (88.4) |  |
 Divorced/widowed/separated | 76 (7.6) | 85 (7.7) |  |
 Unknown | 7 (0.7) | 2 (0.2) |  |
BMI | Â | Â | 0.118 |
  ≤ 23.9 | 619 (61.7) | 722 (65.2) |  |
 24.0–27.9 | 290 (28.9) | 297 (26.8) |  |
  ≥ 28.0 | 92 (9.2) | 80 (7.2) |  |
 Unknown | 2 (0.2) | 8 (0.7) |  |
Age at menarche (years) | Â | Â | 0.068 |
  ≤ 12.0 | 125 (12.5) | 170 (15.4) |  |
  > 12.0 | 865 (86.2) | 927 (83.7) |  |
 Unknown | 13 (1.3) | 10 (0.9) |  |
Menopausal status | Â | Â | 0.025 |
 Pre-menopausal | 569 (56.7) | 575 (51.9) |  |
 Post-menopausal | 431 (43.0) | 531 (48.0) |  |
 Unknown | 3 (0.3) | 1 (0.1) |  |
Parity | Â | Â | 0.796 |
 0 | 70 (7.0) | 74 (6.7) |  |
  ≥ 1 | 931 (92.8) | 1030 (93.0) |  |
 Unknown | 2 (0.2) | 3 (0.3) |  |
Breastfeeding | Â | Â | 0.314 |
 Never | 151 (15.1) | 194 (17.5) |  |
 Ever | 795 (79.3) | 901 (81.4) |  |
 Unknown | 57 (5.7) | 12 (1.1) |  |
Breast cancer history | Â | Â | 0.099 |
 No | 949 (94.6) | 1067 (96.4) |  |
 Yes | 37 (3.7) | 27 (2.4) |  |
 Unknown | 17 (1.7) | 13 (1.2) |  |
Oral contraceptive use | Â | Â | 0.560 |
 No | 871 (86.8) | 865 (78.1) |  |
 Yes | 73 (7.3) | 80 (7.2) |  |
 Unknown | 59 (5.9) | 162 (14.6) |  |