Table 1.
Characteristics of the study population relative to case and control status
| Characteristic | Cases (n = 864) Mean (± SD) or count (%) |
Controls (n = 418) Mean (± SD) or count (%) |
|---|---|---|
| Age at mammogram (years) | 57.5 (± 10.8) | 57.3 (± 10.6) |
| BMI (kg/m2) | 26.1 (± 5.0) | 24.6 (± 3.8) |
| Age at last menstruation {years} | 48.7 (± 5.5) | 47.5 (± 6.6) |
| Age at first menarche (years) | 13.5 (± 1.6) | 13.4 (± 1.4) |
| Age at FTP (years) | 25.2 (± 4.6) | 25.6 (± 4.4) |
| Menopausal status | ||
| Premenopausal | 221 (30.9%) | 105 (26.6%) |
| Postmenopausal | 495 (69.1%) | 209 (73.4%) |
| Parity | ||
| No birth | 125 (15.5%) | 54 (14.3%) |
| 1 to 2 births | 507 (62.7%) | 202 (53.4%) |
| ≥ 3 births | 177 (21.9%) | 122 (32.3%) |
| Family history of breast cancer | ||
| No | 700 (85.6%) | 237 (80.3%) |
| Yes | 118 (14.4%) | 58 (19.7%) |
| HRT ever | ||
| No | 564 (70.2%) | 156 (42.5%) |
| Yes | 239 (29.8%) | 211 (57.5%) |
For the cases, age is identical with age at diagnosis. BMI, body mass index; FTP, first term pregnancy; HRT, hormone replacement therapy.