Table 1.
Characteristics of cases and controls
| Cases | Controls | |||
|---|---|---|---|---|
| N | (%) | N | (%) | |
| Age (years) | ||||
| 20–34 | 182 | (24.3) | 125 | (30.9) |
| 35–39 | 285 | (38.0) | 142 | (35.1) |
| 40–44 | 128 | (17.1) | 77 | (19.0) |
| 45–49 | 155 | (20.7) | 61 | (15.1) |
| Any first-degree relative with breast cancer | ||||
| No | 661 | (88.1) | 379 | (93.6) |
| Yes | 89 | (11.9) | 26 | (6.4) |
| Age at menarche (years) | ||||
| <12 | 148 | (19.7) | 66 | (16.3) |
| 12 | 148 | (19.7) | 98 | (24.2) |
| 13 | 231 | (30.8) | 113 | (27.9) |
| ≥14 | 218 | (29.1) | 128 | (31.6) |
| Missing | 5 | (0.7) | 0 | (0.0) |
| Age at first live birth (years) | ||||
| <20 | 50 | (6.7) | 31 | (7.7) |
| 20–24 | 162 | (21.6) | 86 | (21.2) |
| 25–29 | 225 | (30.0) | 109 | (26.9) |
| ≥30 | 128 | (17.1) | 64 | (15.8) |
| No live birth | 185 | (24.7) | 115 | (28.4) |
| Estrogen receptor status | ||||
| Negative | 155 | (20.7) | ||
| Positive | 261 | (34.8) | ||
| Missing | 334 | (44.5) | ||
| Progesterone receptor status | ||||
| Negative | 118 | (15.7) | ||
| Positive | 298 | (39.7) | ||
| Missing | 334 | (44.5) | ||