Table 1 Characteristics of breast cancer cases and cancer-free controls
| Â | Cases (n = 715) (%) | Controls (n = 1430) (%) | P |
|---|---|---|---|
Age (year) | Â | Â | Â |
  ≤29 | 10 (1.4) | 25 (1.8) |  |
  30-39 | 83 (11.6) | 184 (12.9) |  |
  40-49 | 195 (27.3) | 387 (27.1) |  |
  50-59 | 231 (32.3) | 439 (30.7) |  |
  60-69 | 147 (20.6) | 295 (20.6) |  |
  70-79 | 49 (6.9) | 100 (7.0) | 0.93 |
  Mean age ± SD | 52.4 ± 11.1 | 52.0 ± 11.3 | 0.410 |
Menopausal status | Â | Â | Â |
  Premenopausal | 340 (47.6) | 680 (47.6) |  |
  Postmenopausal | 373 (52.2) | 746 (52.2) | 1.00 |
  Unknown | 2 (0.3) | 4 (0.3) |  |
Age at menarche(year) | Â | Â | Â |
  ≤12 | 234 (32.7) | 408 (28.5) |  |
  13-14 | 336 (47.0) | 670 (46.9) |  |
  ≥15 | 137 (19.2) | 326 (22.8) | 0.06 |
  Unknown | 8 (1.1) | 26 (1.8) |  |
  Mean age ± SD | 13.3 ± 1.6 | 13.5 ± 1.7 | 0.040 |
Parity | Â | Â | Â |
  0 | 103 (14.4) | 216 (15.1) |  |
  1-2 | 462 (64.6) | 895 (62.6) |  |
  ≥3 | 150 (21.0) | 312 (21.8) | 0.74 |
  Unknown | 0 (0) | 7 (0.5) |  |
Age at first live birth (year) | Â | Â | Â |
  17-23 | 114 (15.9) | 278 (19.4) |  |
  24-27 | 302 (42.2) | 614 (42.9) |  |
  ≥28 | 191 (26.7) | 304 (21.3) |  |
  No birth | 103 (14.4) | 216 (15.1) | 0.02 |
  Unknown | 5 (0.7) | 18 (1.3) |  |
  Mean age ± SD | 26.2 ± 3.4 | 25.9 ± 3.6 | 0.04 |
Age at menopause (year) (postmenopausal women only) | Â | ||
  ≤49 | 128 (34.4) | 247 (33.1) |  |
  ≥50 | 238 (63.8) | 489 (65.6) | 0.64 |
  Unknown | 7 (1.9) | 10 (1.3) |  |
  Mean age ± SD | 49.6 ± 5.0 | 49.4 ± 5.1 | 0.71 |
BMI (kg/m2) | Â | Â | Â |
  <18.5 | 59 (8.3) | 150 (10.5) |  |
  18.5-21.9 | 293 (41.0) | 679 (47.5) |  |
  22–24.9 | 210 (29.4) | 379 (26.5) |  |
  ≥25 | 148 (20.7) | 210 (14.7) | < 0.001 |
  Unknown | 5 (0.7) | 12 (0.8) |  |
  Mean BMI ± SD | 22.5 ± 3.3 | 21.9 ± 3.2 | < 0.001 |
Alcohol consumption (g/day) | Â | Â | Â |
  Never | 444 (62.1) | 900 (62.9) |  |
  Lighta | 124 (17.3) | 277 (19.4) |  |
  Moderateb | 84 (11.8) | 166 (11.6) |  |
  Heavyc | 56 (7.8) | 81 (5.7) | 0.2 |
  Unknown | 7 (1.0) | 6 (0.4) |  |
Smoking (pack/year) | Â | Â | Â |
  Never | 594 (83.1) | 1173 (82.0) |  |
  <20 | 79 (11.1) | 162 (11.3) |  |
  ≥20 | 34 (4.8) | 84 (5.9) | 0.560 |
  Unknown | 8 (1.1) | 11 (0.8) |  |
Total exercise (hour/day) | Â | Â | Â |
  No | 200 (28.0) | 407 (28.5) |  |
  <0.5 | 279 (39.0) | 629 (44.0) |  |
  ≥0.5 | 228 (31.9) | 384 (26.9) | 0.03 |
  Unknown | 8 (1.1) | 10 (0.7) |  |
Family history of breast cancer | Â | Â | Â |
  Yes | 59 (8.3) | 94 (6.6) |  |
  No | 656 (91.8) | 1336 (93.4) | 0.16 |
Hormone use | Â | Â | Â |
  Yes | 98 (13.7) | 197 (13.8) |  |
  No | 604 (84.5) | 1189 (83.2) | 0.88 |
  Unknown | 13 (1.8) | 44 (3.1) |  |
Referral pattern to our hospital | Â | Â | Â |
  Patient's discretion | 205 (28.7) | 496 (34.7) |  |
  Family recommendation | 154 (21.5) | 244 (17.1) |  |
  Referral from other clinics | 206 (28.8) | 251 (17.6) |  |
  Secondary screening after primary screening | 139 (19.4) | 431 (30.1) |  |
  Others | 6 (0.8) | 4 (0.3) | < 0.001 |
  Unknown | 5 (0.7) | 4 (0.3) |  |
Tumor subtype | Â | Â | Â |
Luminal (ER and/or PR+ and HER2 -) | 455 (63.6) | Â | Â |
Luminal HER2 (ER and/or PR+ and HER2+) | 108 (15.1) | Â | Â |
HER2 rich (ER and PR- and HER2+) | 84 (11.8) | Â | Â |
Triple negative (ER and PR- and HER2-) | 68 (9.5) | Â | Â |