Table 1.
Characteristics obtained at the first breast density measurement for each woman by Breast Imaging Reporting and Data System (BI-RADS; mammographic breast density category) in the Breast Cancer Surveillance Consortium, 1995 to 2009
| Characteristic | Breast density | ||||
|---|---|---|---|---|---|
| Total | BI-RADS 1, almost entirely fatty | BI-RADS 2, scattered fibroglandular densities | BI-RADS 3, heterogenously dense | BI-RADS 4, extremely dense | |
| (n = 724603) % | (n = 69150) % | (n = 306089) % | (n = 276710) % | (n = 72654) % | |
| Age, y | |||||
| 40–49 | 46.8 | 26.7 | 38.0 | 55.5 | 69.1 |
| 50–59 | 27.7 | 28.2 | 30.1 | 26.7 | 21.5 |
| 60–69 | 15.8 | 26.0 | 19.5 | 11.6 | 6.4 |
| 70–79 | 9.7 | 19.1 | 12.4 | 6.1 | 3.1 |
| Race/ethnicity | |||||
| White, non-Hispanic | 73.4 | 70.7 | 74.3 | 73.3 | 72.4 |
| Black, non-Hispanic | 2.3 | 3.4 | 2.4 | 2.1 | 1.6 |
| Asian | 7.6 | 4.0 | 5.3 | 9.2 | 14.1 |
| Hispanic | 13.6 | 17.2 | 14.6 | 12.8 | 9.5 |
| Other/mixed | 3.1 | 4.7 | 3.4 | 2.7 | 2.3 |
| Missing* | (6.7) | (9.1) | (7.0) | (6.1) | (5.6) |
| Body mass index, kg/m2 | |||||
| <18.5 | 1.8 | 0.6 | 1.0 | 2.0 | 5.8 |
| 18.5 to <25 | 46.5 | 20.8 | 37.3 | 55.7 | 72.6 |
| 25 to <30 | 28.9 | 30.4 | 32.8 | 27.5 | 16.3 |
| ≥30 | 22.8 | 48.2 | 28.9 | 14.8 | 5.2 |
| Missing* | (16.4) | (17.7) | (17.4) | (15.7) | (13.9) |
| Parity status | |||||
| Parous | 82.6 | 86.6 | 86.1 | 80.4 | 72.4 |
| Nulliparous | 17.4 | 13.4 | 13.9 | 19.6 | 27.6 |
| Missing* | (13.1) | (14.6) | (13.7) | (12.1) | (12.7) |
| Menopausal status | |||||
| Premenopausal | 45.8 | 23.1 | 36.4 | 55.7 | 70.2 |
| Postmenopausal | 54.2 | 76.9 | 63.6 | 44.3 | 29.8 |
| Missing* | (14.6) | (12.9) | (14.2) | (15.6) | (14.6) |
| Oral contraceptive use† | |||||
| Yes | 2.9 | 1.3 | 2.1 | 3.8 | 4.7 |
| No | 51.4 | 52.4 | 48.3 | 53.7 | 54.6 |
| Missing‡ | 45.7 | 46.3 | 49.6 | 42.5 | 40.7 |
| Hormone therapy use† | |||||
| Yes | 18.6 | 17.4 | 19.8 | 18.5 | 14.5 |
| No | 81.4 | 82.6 | 80.2 | 81.5 | 85.5 |
| Missing* | (9.3) | (8.4) | (9.4) | (9.6) | (8.7) |
| Prior diagnosis of breast cancer | |||||
| Yes | 3.4 | 3.7 | 3.9 | 3.1 | 2.5 |
| No | 96.6 | 96.3 | 96.1 | 96.9 | 97.5 |
| Missing* | (6.7) | (6.8) | (7.4) | (5.9) | (6.7) |
| First-degree family history of breast or ovarian cancer | |||||
| Yes | 13.6 | 13.0 | 13.4 | 13.8 | 13.9 |
| No | 86.4 | 87.0 | 86.6 | 86.2 | 86.1 |
| Missing* | (4.5) | (4.9) | (4.1) | (4.8) | (4.6) |
* Percentage of total.
† At time of mammogram.
‡ Retained in analysis.