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Table 1 Characteristics of breast cancer case-patient participants and control participants by study
| Overall | Women’s CARE Study | Women’s BCIS Study | Women’s LIFE Study | ||||
|---|---|---|---|---|---|---|---|
| Number of cases (%) | Number of controls (%) | Number of cases (%) | Number of controlsa (%) | Number of cases (%) | Number of cases (%) | Number of controls (%) | |
| Number of participants | 3934 | 2386 | 1873 | 1982 | 517 | 1544 | 404 |
| Subtype of breast cancer | |||||||
| Unclassified | 1151 | ─ | 691 | ─ | 182 | 278 | ─ |
| Classified | 2783 | ─ | 1182 | ─ | 335 | 1266 | ─ |
| Triple negative (ER–/PR–/HER2–) | 515 (18.5) | ─ | 329 (27.8) | ─ | 21 (6.3) | 165 (13.0) | ─ |
| Luminal-like (ER+ and/or PR+) | 2056 (73.9) | 758 (64.1) | 277 (82.7) | 1021 (80.7) | |||
| HER2-enriched (ER–/PR–/HER2+) | 212 (7.6) | ─ | 95 (8.0) | ─ | 37 (11.0) | 80 (6.3) | ─ |
| Mean age at reference date, years (SD) | 47.3 (7.4) | 47.9 (8.1) | 48.9 (8.5) | 48.8 (8.4) | 51.5 (7.3) | 44.0 (3.9) | 43.5 (3.8) |
| Menopausal status | |||||||
| Premenopausal | 2427 (61.7) | 1257 (52.7) | 929 (49.6) | 927 (46.8) | 203 (39.3) | 1295 (83.9) | 330 (81.7) |
| Postmenopausal | 1507 (38.3) | 1129 (47.3) | 944 (50.4) | 1055 (53.2) | 314 (60.7) | 249 (16.1) | 74 (18.3) |
| Never used MHT | 650 (43.1) | 466 (41.3) | 409 (43.3) | 430 (40.8) | 107 (34.1) | 134 (53.8) | 36 (48.7) |
| Ever used MHT | 857 (56.9) | 663 (58.7) | 535 (56.7) | 625 (59.2) | 207 (65.9) | 115 (46.2) | 38 (51.3) |
| Race | |||||||
| White | 2849 (72.4) | 1503 (63.0) | 1056 (56.4) | 1134 (57.2) | 435 (84.1) | 1358 (88.0) | 369 (91.3) |
| African-American | 1085 (27.6) | 883 (37.0) | 817 (43.6) | 848 (42.8) | 82 (15.9) | 186 (12.0) | 35 (8.7) |
| BMI at age 18 years, kg/m2 | |||||||
| < 20.0 | 1921 (48.8) | 1110 (46.5) | 882 (47.1) | 906 (45.7) | 286 (55.3) | 753 (48.8) | 204 (50.5) |
| 20.0–24.9 | 1740 (44.2) | 1061 (44.5) | 848 (45.3) | 893 (45.1) | 207 (40.0) | 685 (44.4) | 168 (41.6) |
| ≥ 25.0 | 273 (6.9) | 215 (9.0) | 143 (7.6) | 183 (9.2) | 24 (4.6) | 106 (6.9) | 32 (7.9) |
| Recent BMI, kg/m2 | |||||||
| < 25.0 | 2292 (58.3) | 1271 (53.3) | 985 (52.6) | 1003 (50.6) | 345 (66.7) | 962 (62.3) | 268 (66.3) |
| 25.0–29.9 | 968 (24.6) | 652 (27.3) | 511 (27.3) | 570 (28.8) | 115 (22.2) | 342 (22.2) | 82 (20.3) |
| ≥ 30.0 | 674 (17.1) | 463 (19.4) | 377 (20.1) | 409 (20.6) | 57 (11.0) | 240 (15.5) | 54 (13.4) |
