Table 1.
Characteristics of participants by age at diagnosis: Australian Breast Cancer Family Study
| Characteristic | Age <35 years (n=201, 16.8%) |
Age 35–39 years (n=336, 28.1%) |
Age 40–49 years (n= 337, 28.2%) |
Age 50–59 years (n=322, 26.9%) |
All (n=1,196, 100%) |
|---|---|---|---|---|---|
| Age at diagnosis (median, IQR), years | 32 (30–33) | 37 (36–38) | 45 (43–48) | 54 (52–57) | 42 (36–50) |
| Year of diagnosis, (n, %) | |||||
| 1992–95 | 88 (43.8) | 150 (44.6) | 46 (13.7) | 35 (10.9) | 319 (26.7) |
| 1996–99 | 113 (56.2) | 186 (55.4) | 291 (86.3) | 287 (89.1) | 877 (73.3) |
| Age at menarche (median, IQR), years | 13 (12–14) | 13 (12–14) | 13 (12–14) | 13 (12–14) | 13 (12–14) |
| Age at first birth (median, IQR), yearsa | 26 (23–28) | 27 (24–30) | 25 (22–29) | 24 (21–27) | 25 (22–29) |
| No. with children (n, %) | 128 (63.7) | 255 (75.9) | 278 (82.5) | 278 (86.3) | 939 (78.5) |
| No. of pregnancies (median, IQR) | 2 (0–3) | 2 (1–3) | 2 (2–3) | 3 (2–4) | 2 (1–3) |
| Use of contraceptive pill (n, %) | |||||
| Ever | 184 (91.5) | 303 (90.2) | 292 (86.7) | 252 (78.3) | 1,031 (86.2) |
| Never | 17 (8.5) | 33 (9.8) | 45 (13.3) | 70 (21.7) | 165 (13.8) |
| Menopausal status (n, %) | |||||
| Premenopausal | 197 (98.0) | 328 (97.6) | 303 (89.9) | 126 (39.1) | 954 (79.8) |
| Postmenopausal | 4 (2.0) | 8 (2.4) | 34 (10.1) | 196 (60.9) | 242 (20.2) |
| Hormone replacement therapy (n, %) | |||||
| No | 199 (99.0) | 323 (96.1) | 299 (88.7) | 140 (43.5) | 961 (80.4) |
| Yes | 2 (1.0) | 11 (3.3) | 38 (11.3) | 181 (56.2) | 232 (19.4) |
| Missing/unknown | 0 (0.0) | 2 (0.6) | 0 (0.0) | 1 (0.3) | 3 (0.2) |
| No. with first- or second-degree blood relatives with invasive breast cancer (n, %) |
|||||
| First degree | 20 (10.0) | 30 (8.9) | 42 (12.5) | 44 (13.7) | 136 (11.4) |
| Second degree | 44 (21.9) | 82 (24.4) | 74 (22.0) | 68 (21.1) | 268 (22.4) |
IQR = interquartile range.
a
For those with at least one live birth.