Table 1 Baseline demographics and breast density estimates by case–control status

Number of women

318

106

Age at menarche

0.02*

Reference group: <12 years (0)

34 (13 %)

26 (25 %)

12–14 years (1)

197 (75 %)

71 (67 %)

15 years or older (2)

32 (12 %)

9 (8 %)

Missing

55

0

Number of previous benign biopsies

0.36

Reference group: 0 (0)

235 (74 %)

74 (70 %)

1 (1)

53 (17 %)

24 (23 %)

2+ (2)

30 (9 %)

8 (8 %)

Missing

0

0

Number of first-degree relatives with breast cancer

0.89

Reference group: 0 (0)

242 (77 %)

83 (78 %)

1 (1)

65 (21 %)

22 (21 %)

2+ (2)

5 (2 %)

1 (1 %)

Missing

6

0

Age at first live birth

0.08

Reference group: Nulliparous (0)

252 (27 %)

17 (16 %)

Before age 30 (1)

167 (53 %)

63 (60 %)

Age 30 or older (2)

65 (20 %)

26 (25 %)

Missing

1

0

Race

0.22

Reference group: Caucasian (0)

162 (64 %)

79 (75 %)

African American (1)

72 (29 %)

21 (20 %)

Asian (2)

10 (4 %)

2 (2 %)

Other (3)

8 (3 %)

3 (3 %)

Missing

66

1

Body mass index

<0.001*

Reference group: Normal weight (0)

161 (59 %)

20 (24 %)

Overweight (1)

75 (28 %)

24 (28 %)

Obese (2)

36 (13 %)

40 (48 %)

Missing

46

22

BI-RADS breast density

0.65

Reference group: Predominantly fatty (0)

21 (7 %)

4 (4 %)

Scattered fibroglandular densities (1)

134 (42 %)

50 (47 %)

Heterogeneously dense (2)

160 (50 %)

51 (48 %)

Extremely dense (3)

3 (1 %)

1 (1 %)

LIBRA: absolute dense area, mean ± SD

31.3 cm² ± 17.8

48.5 cm² ± 29.4

<0.001*

LIBRA: area percent density, mean ± SD

27.1 % ± 14.7

31.9 % ± 15.5

<0.001*

Quantra: absolute dense volume, mean ± SD

73.1 cm³ ± 50.0

121.7 cm³ ± 98.9

<0.001*

Quantra: volume percent density, mean ± SD

11.6 % ± 6.4

13.6 % ± 6.9

0.002*