Table 1. Demographic and risk factor characteristics of the study population, according to the use of hormonal contraceptive and hormone replacement therapy.
| Premenopausal | Postmenopausal | |||||
| Characteristics | HC non-users | HC users | P-value | HRT non-users | HRT users | P-value |
| Age (years) | ||||||
| < 40 | 314 (66.9) | 244 (57.8) | 32 (3.6) | 5 (2.3) | ||
| 40–54 | 150 (32) | 173 (41) | 0.016 | 294 (32.8) | 81 (36.8) | 0.167 |
| 55–64 | 4 (0.9) | 5 (1.2) | 403 (44.9) | 105 (47.7) | ||
| ≥ 65 | 1 (0.2) | - | 168 (18.7) | 29 (13.2) | ||
| BMI (kg/m2) | ||||||
| < 25 | 96 (20.5) | 78 (18.5) | 120 (13.4) | 34 (15.5) | ||
| 25–29.9 | 197 (42.0) | 185 (43.9) | 0.732 | 335 (37.3) | 92 (41.8) | 0.217 |
| ≥ 30 | 176 (37.5) | 159 (37.7) | 442 (49.3) | 94 (42.7) | ||
| Age at menarche | ||||||
| < 13 | 222 (47.3) | 204 (48.3) | 0.764 | 344 (38.4) | 99 (45) | 0.071 |
| ≥ 13 | 247 (52.7) | 218 (51.7) | 553 (61.6) | 121 (55) | ||
| Family history of breast cancer | ||||||
| No | 440 (93.8) | 402 (95.3) | 0.345 | 851 (94.9) | 212 (96.4) | 0.355 |
| yes | 29 (6.2) | 20 (4.7) | 46 (5.1) | 8 (3.6) | ||
| Socio economic status | ||||||
| Low | 139 (29.6) | 130 (30.8) | 341 (38) | 45 (20.4) | ||
| Medium | 141 (30.1) | 126 (29.8) | 0.925 | 264 (29.4) | 59 (26.8) | < 0.001 |
| High | 189 (40.3) | 166 (39.3) | 292 (32.6) | 116 (52.7) | ||
| Age at 1rst full term pregnancy | ||||||
| Nulliparous | 67 (14.3) | 18 (4.3) | 68 (7.6) | 25 (11.3) | ||
| < 22 | 188 (40.1) | 242 (57.3) | < 0.001 | 455 (50.7) | 105 (47.7) | 0.215 |
| ≥ 22 | 209 (44.5) | 156 (36.9) | 365 (40.7) | 86 (39.1) | ||
| Missing | 5 (1.1) | 6 (1.4) | 9 (1) | 4 (1.8) | ||
| Number of full term pregnancies | ||||||
| 0 | 67 (14.3) | 18 (4.3) | 68 (7.6) | 25 (11.4) | ||
| 1−2 | 203 (43.3) | 151 (35.8) | < 0.001 | 210 (23.4) | 60 (27.3) | 0.087 |
| ≥ 3 | 195 (41.6) | 253 (59.9) | 615 (68.6) | 133 (60.4) | ||
| Missing | 4 (0.8) | - | 4 (0.4) | 2 (0.9) | ||
| Breastfeeding | ||||||
| Nulliparous | 67 (14.3) | 18 (4.3) | 68 (7.6) | 25 (11.3) | ||
| < 12 | 43 (9.2) | 49 (11.6) | < 0.001 | 92 (10.3) | 31 (14.1) | 0.010 |
| ≥ 12 | 124 (26.4) | 142 (33.6) | 168 (18.7) | 51 (23.2) | ||
| Missing | 235 (50.1) | 213 (50.5) | 569 (63.4) | 113 (51.4) | ||
| Native ancestry | ||||||
| 0–50% | 113 (24.1) | 117 (27.7) | 244 (27.2) | 64 (29.1) | ||
| 51–75% | 205 (43.7) | 199 (47.2) | 0.093 | 367 (40.9) | 90 (40.9) | 0.047 |
| 76–100% | 106 (22.6) | 80 (18.9) | 199 (22.2) | 34 (15.5) | ||
| Missing | 45 (9.6) | 26 (6.2) | 87 (9.7) | 32 (14.5) | ||
P-value (Chi2 or Fisher’s exact tests) for the difference between HC non-users and users in premenopausal, and HRT non-users and users in postmenopausal women.