Table 1 Characteristics of study sample
From: Combining quantitative and qualitative breast density measures to assess breast cancer risk
|  | Invasive breast cancer cases (n = 1720) | Matched control subjects (n = 3686) |
|---|---|---|
Age, years, mean (SD) | 59.5 (12.1) | 59.6 (12.0) |
Body mass index, kg/m2, mean (SD) | 26.3 (5.7) | 26.2 (5.7) |
Dense breast volume,a ml, median (IQR) | 57.8 (41.0–82.5) | 50.7 (36.8–70.2) |
Age at first live birth, n (%) | ||
  < 30 years | 856 (50.1%) | 2085 (56.6%) |
 None or ≥ 30 years | 852 (49.9%) | 1600 (43.4%) |
Family history of breast cancer,b n (%) | ||
 No | 1218 (71.2%) | 2991 (81.2%) |
 Yes | 493 (28.8%) | 693 (18.8%) |
History of breast biopsy, n (%) | ||
 No | 1304 (76.4%) | 3040 (82.6%) |
 Yes | 402 (23.6%) | 641 (17.4%) |
Race/ethnicity, n (%) | ||
 White | 1380 (80.3%) | 3012 (81.7%) |
 Asian | 218 (12.7%) | 437 (11.9%) |
 Black | 34 (2.0%) | 67 (1.8%) |
 Hispanic | 37 (2.2%) | 101 (2.7%) |
 Other | 50 (2.9%) | 69 (1.9%) |
BI-RADS breast density,c n (%) | ||
 Almost entirely fat (a) | 233 (13.5%) | 731 (19.8%) |
 Scattered fibroglandular densities (b) | 668 (38.8%) | 1557 (42.2%) |
 Heterogeneously dense (c) | 600 (34.9%) | 1115 (30.2%) |
 Extremely dense (d) | 219 (12.7%) | 283 (7.7%) |