Table S2. Summary characteristics of study population by training or test subgroups.
Characteristic
Training set
Test set
(733 breast cancer cases and 748
controls)
(765 breast cancer cases and 747 controls)
Median
Percent density (%)
Absolute dense area (cm2)
13.5
19.9
14.3
20.8
0.228
0.443
Mean (SD)
Age at diagnosis or reference date (y)
Age at mammogram (y)
Age at menarche (y)
Age at menopause (y)
BMI at diagnosis or reference date (kg/m2)
Alcohol consumption (g/day)
Percent density (%)
Absolute dense area (cm2)
62.1 (7.0)
61.8 (7.0)
13.6 (1.4)
50.3 (3.9)
25.2 (3.7)
2.3 (4.2)
17.9 (15.2)
26.4 (22.6)
61.9 (7.1)
61.6 (7.1)
13.5 (1.4)
50.3 (3.7)
25.1 (3.7)
2.7 (5.0)
18.5 (15.8)
27.1 (23.1)
0.375
0.359
0.421
0.781
0.839
0.235
0.454
0.441
576 (38.9)
531 (35.9)
301 (20.3)
70 (4.7)
3 (0.2)
581 (38.4)
513 (33.9)
333 (22.0)
83 (5.5)
2 (0.1)
367 (24.8)
513 (34.6)
388 (26.2)
153 (10.3)
47 (3.2)
13 (0.9)
396 (26.2)
467 (30.9)
419 (27.7)
172 (11.4)
39 (2.6)
19 (1.3)
165 (11.1)
550 (37.1)
408 (27.5)
208 (14.0)
30 (2.0)
119 (8.0)
173 (11.4)
561 (37.1)
411 (27.2)
227 (15.0)
30 (2.0)
109 (7.2)
806 (54.4)
673 (45.4)
2 (0.1)
155 (10.5)
163 (11.0)
760 (50.3)
750 (49.6)
2 (0.1)
171 (11.3)
188 (12.4)
Frequency, number (%)
Categorical percent density (%)
<10
10-24
25-49
50-74
≥75
Categorical absolute dense area (cm2)
<10
10-24
25-49
50-74
75-99
≥100
Parity and age at first birth
Nulliparous
1-3 children, age at first birth <25y
1-3 children, age at first birth 25-29y
1-3 children, age at first birth ≥30y
≥4 children, age at first birth <25y
≥4 children, age at first birth ≥25y
Hormone replacement therapy
Never used hormones
Ever used hormones
Unknown status of hormone use
Family history of breast cancer (Ever)
Benign breast disease (Ever)
P
0.570
0.213
0.939
0.074
0.603
0.247