Table 2.
Risk factors in the Ella study by family history of breast cancer* ( n =914)
| Risk factor | First-degree family history | No first-degree family history |
|---|---|---|
| ( n =135) | ( n =779) | |
| n (%) | n (%) | |
| Age at diagnosis, y | ||
| < 50 | 58 (43.0) | 361 (46.3) |
| ≥ 50 | 77 (57.0) | 418 (53.7) |
| Mean ± SD | 53.6 ± 12.0 | 52.1 ± 12.4 |
| Age at menarche, y | ||
| <13 | 65 (48.1) | 346 (44.4) |
| ≥ 13 | 70 (51.9) | 433 (55.6) |
| Mean ± SD | 12.6 ± 1.6 | 12.8 ± 1.7 |
| Parity | ||
| Nulliparous | 13 (9.6) | 75 (9.6) |
| 1–2 children | 36 (26.7) | 244 (31.3) |
| ≥ 3 children | 86 (63.7) | 460 (59.1) |
| Mean ± SD | 3.3 ± 2.2 | 3.1 ± 2.3 |
| Age at first full term pregnancy, y | ||
| < 21 | 41 (33.6) | 288 (40.9) |
| 21–24 | 38 (31.1) | 183 (26.0) |
| ≥ 25 | 43 (35.2) | 232 (33.0) |
| Unknown | 0 | 1 (.1) |
| Nulliparous | 13 | 75 |
| Mean ± SD | 23.4 ± 5.6 | 22.8 ± 5.4 |
| Time since last full-term pregnancy, y | ||
| > 10 | 40 (69.0) | 216 (60.7) |
| ≤ 10 | 18 (31.0) | 140 (39.3) |
| Postmenopausal or unknown | 70 | 383 |
| Premenopausal but nulliparous | 7 | 40 |
| Mean ± SD | 12.8 ± 6.9 | 13.4 ± 8.0 |
| Time from menarche to first pregnancy, y | ||
| < 8 | 32 (26.2) | 277 (39.3) |
| 8–12 | 51 (41.8) | 221 (31.5) |
| ≥ 13 | 39 (32.0) | 205 (29.1) |
| Unknown | 0 | 1 (0.1) |
| Nulliparous | 13 | 75 |
| Mean ± SD | 10.9 ± 5.6 | 9.9 ± 5.7 |
| Lifetime duration of breastfeeding, mo | ||
| Never | 31 (25.4) | 170 (24.1) |
| Up to 12 | 48 (39.3) | 248 (35.2) |
| ≥ 12 | 43 (35.2) | 286 (40.6) |
| Nulliparous | 13 | 75 |
| Mean ± SD | 15.6 ± 26.2 | 18.6 ± 31.5 |
| Breastfeeding duration per birth, mo | ||
| Never | 31 (25.4) | 170 (24.2) |
| > 0–5 | 54 (44.3) | 269 (38.2) |
| ≥ 5 | 37 (30.3) | 265 (37.6) |
| Nulliparous | 13 | 75 |
| Mean ± SD | 4.5 ± 6.6 | 5.3 ± 6.8 |
| Menopausal status at diagnosis | ||
| Pre | 64 (47.8) | 386 (50.2) |
| Post | 70 (52.2) | 383 (49.8) |
| Unknown | 1 | 10 |
| Age at menopause, y | ||
| < 50 | 41 (58.6) | 226 (59) |
| ≥ 50 | 29 (41.4) | 157 (41) |
| Premenopausal at diagnosis | 64 | 386 |
| Unknown | 1 | 10 |
| Mean ± SD | 46.9 ± 6.9 | 47.3 ± 6.5 |
| Hormone replacement therapy | ||
| Never | 117 (87.3) | 674 (87.3) |
| Ever | 17 (12.7) | 98 (12.7) |
| Unknown | 1 | 7 |
| Hormone contraceptive use | ||
| Never | 58 (43.0) | 345 (44.3) |
| Ever | 77 (57.0) | 434 (55.7) |
| Tertile of duration of menstruation, y | ||
| 7.6–27.35 | 21 (15.6) | 172 (22.1) |
| 27.4–33.45 | 40 (29.6) | 201 (25.8) |
| 33.5–50.5 | 65 (48.1) | 343 (44) |
| Unknown | 9 (6.7) | 63 (8.1) |
| Mean ± SD | 33.2 ± 6.7 | 32.1 ± 7.3 |
| Country of residence | ||
| Mexico | 46 (11.5) | 355 (88.5) |
| U.S. | 89 (17.3) | 424 (82.7) |
*History of breast cancer in one or more first-degree relatives.