Distribution of breast cancer risk factors by quintiles of percent and absolute dense volume
| Percent dense volume (%) | Absolute dense volume (cm3) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q1 (<4.9) | Q2 (4.9–6.5) | Q3 (6.6–9.0) | Q4 (9.1–13.0) | Q5 (>13.0) | Q1 (<39) | Q2 (39–50) | Q3 (51–63) | Q4 (64–83) | Q5 (>83) | |||
| N = 8,221 | N = 8,220 | N = 8,221 | N = 8,220 | N = 8,220 | P trend | N = 8,221 | N = 8,220 | N = 8,221 | N = 8,220 | N = 8,220 | P trend | |
| Age (years), mean | 59.1 | 57.9 | 55.9 | 52.7 | 49.3 | <0.001 | 56.6 | 56.8 | 55.7 | 54.2 | 51.6 | <0.001 |
| BMI (kg/m2), mean | 29.2 | 26.6 | 25.0 | 23.7 | 22.4 | <0.001 | 23.2 | 25.0 | 25.8 | 26.3 | 26.4 | <0.001 |
| Age at menarche (years), mean | 13.0 | 13.1 | 13.1 | 13.2 | 13.2 | <0.001 | 13.2 | 13.2 | 13.1 | 13.1 | 13.0 | <0.001 |
| Parity, % | <0.001 | <0.001 | ||||||||||
| 0 | 11.8 | 10.9 | 11.5 | 12.1 | 14.3 | 8.7 | 10.0 | 11.7 | 13.7 | 16.6 | ||
| 1 | 14.2 | 13.6 | 13.9 | 14.0 | 14.9 | 12.6 | 12.4 | 13.9 | 14.9 | 16.8 | ||
| 2 | 47.2 | 47.6 | 48.0 | 50.0 | 47.7 | 48.5 | 50.2 | 48.8 | 48.0 | 47.1 | ||
| ≥3 | 26.8 | 27.9 | 26.7 | 23.9 | 21.0 | 30.2 | 27.5 | 25.7 | 23.4 | 19.5 | ||
| Age at first birth (years), mean | 25.6 | 26.1 | 26.9 | 27.8 | 28.9 | <0.001 | 26.9 | 26.7 | 26.7 | 27.0 | 28.0 | <0.001 |
| Menopausal status, % | <0.001 | <0.001 | ||||||||||
| Premenopausal | 21.5 | 26.3 | 34.7 | 50.1 | 68.3 | 32.5 | 31.3 | 35.9 | 44.0 | 57.2 | ||
| Perimenopausal/unknown | 2.8 | 3.3 | 3.5 | 3.6 | 3.1 | 2.7 | 2.9 | 3.3 | 3.6 | 3.8 | ||
| Postmenopausal | 75.7 | 70.4 | 61.8 | 46.3 | 28.6 | 64.8 | 65.8 | 60.8 | 52.4 | 39.0 | ||
| Ever OC use, % | 74.3 | 78.3 | 80.4 | 82.2 | 83.3 | <0.001 | 78.8 | 79.4 | 79.5 | 79.8 | 81.2 | 0.003 |
| HRT use, %a | <0.001 | 0.19 | ||||||||||
| Never | 70.1 | 69.1 | 68.4 | 67.7 | 69.3 | 69.1 | 69.0 | 69.4 | 69.1 | 67.9 | ||
| Former | 26.0 | 26.2 | 25.5 | 24.4 | 21.6 | 25.5 | 25.7 | 25.1 | 25.2 | 24.4 | ||
| Current | 4.0 | 4.6 | 6.1 | 8.0 | 9.1 | 0.001 | 5.4 | 5.3 | 5.5 | 5.7 | 7.9 | |
| Benign breast disease, % | 17.8 | 20.6 | 22.0 | 24.0 | 26.4 | <0.001 | 20.7 | 21.2 | 20.8 | 22.9 | 25.2 | <0.001 |
| Family history breast cancer, % | 12.7 | 13.0 | 13.1 | 13.6 | 13.7 | 0.03 | 12.3 | 12.9 | 13.4 | 13.3 | 14.2 | 0.001 |
↵aIn postmenopausal women only. Percent and absolute dense volumes were derived from the mediolateral oblique view.