Table 1 Baseline characteristics at screening examination of study participants
From: Microcalcifications, mammographic breast density, and risk of breast cancer: a cohort study
Characteristic | No breast cancer development n = 3 852 500 | (%) | Breast cancer development n = 58 315 | (%) |
|---|---|---|---|---|
Age (years) | ||||
Mean/SD | 54.07/ 9.39 | 51.55/ 8.53 | ||
BMI status (kg/m2) | ||||
< 23 | 1 557 014 | (40.4) | 24 644 | (42.3) |
≥ 23 | 2 294 644 | (59.6) | 33 656 | (57.7) |
Missing | 842 | (0.0) | 15 | (0.0) |
Age at menarche (years) | ||||
< 15 | 859 664 | (22.3) | 17 196 | (29.5) |
≥ 15 | 2 866 951 | (74.4) | 39 252 | (67.3) |
Missing | 125 885 | (3.3) | 1 867 | (3.2) |
Menopausal status | ||||
No | 1 585 111 | (41.1) | 31 567 | (54.1) |
Yes | 2 201 388 | (57.1) | 25 724 | (44.1) |
Missing | 66 001 | (1.7) | 1 024 | (1.8) |
Age at menopause (years) | ||||
Premenopausal | 1 585 111 | (41.1) | 31 567 | (54.1) |
< 52 | 1 312 303 | (34.1) | 13 860 | (23.8) |
≥ 52 | 755 358 | (19.6) | 10 033 | (17.2) |
Missing | 199 728 | (5.2) | 2 855 | (4.9) |
Parity | ||||
Nulliparous | 135 055 | (3.5) | 3 034 | (5.2) |
Parous | 3 653 852 | (94.8) | 54 292 | (93.1) |
Missing | 63 593 | (1.7) | 989 | (1.7) |
Breastfeeding | ||||
Never | 513 723 | (13.3) | 10 360 | (17.8) |
Ever | 3 261 612 | (84.7) | 46 730 | (80.1) |
Missing/NA | 77 165 | (2.0) | 1 225 | (2.1) |
Oral contraceptive use | ||||
Never | 3 047 538 | (79.1) | 46 300 | (79.4) |
Ever | 735 719 | (19.1) | 10 952 | (18.8) |
Missing | 69 243 | (1.8) | 1 063 | (1.8) |
Family history of breast cancer in a first-degree relative | ||||
No | 3 794 665 | (98.5) | 56 470 | (96.8) |
Yes | 57 835 | (1.5) | 1 845 | (3.2) |
Physical activity | ||||
No | 1 099 679 | (28.5) | 15 240 | (26.1) |
Yes | 2 719 111 | (70.6) | 42 607 | (73.1) |
Missing | 33 710 | (0.9) | 468 | (0.8) |
Smoking status | ||||
Never smoked | 3 667 715 | (95.2) | 55 157 | (94.6) |
Ever smoked | 167 886 | (4.4) | 2 897 | (5.0) |
Missing | 16 899 | (0.4) | 261 | (0.4) |
Drinking status | ||||
No drinking | 3 096 440 | (80.4) | 45 263 | (77.6) |
Drinking | 727 857 | (18.9) | 12 613 | (21.6) |
Missing | 28 203 | (0.7) | 439 | (0.8) |
Hormone replacement therapy | ||||
Premenopausal | 1 585 111 | (41.1) | 31 567 | (54.1) |
Never | 1 762 573 | (45.8) | 19 146 | (32.8) |
Ever | 426 097 | (11.1) | 6 685 | (11.5) |
Missing | 78 719 | (2.0) | 917 | (1.6) |
Microcalcification | ||||
No | 3 842 846 | (99.7) | 57 791 | (99.1) |
Yes | 9 654 | (0.3) | 524 | (0.9) |
BI-RADS breast density classification | ||||
1—Almost fatty | 1 227 502 | (31.9) | 10 599 | (18.2) |
2—Scattered fibroglandular densities | 1 144 267 | (29.7) | 15 421 | (26.4) |
3—Heterogeneously dense | 1 021 547 | (26.5) | 20 566 | (35.3) |
4—Extremely dense | 459 184 | (11.9) | 11 729 | (20.1) |