Table 1. Characteristics of women with invasive breast cancer and controls.
|
Cases (N=2449)
|
Controls (N=14396)
|
|||
|---|---|---|---|---|
| n | % | n | % | |
| Age at diagnosis/reference date | ||||
| 30–39 | 92 | 3.8 | 507 | 3.5 |
| 40–49 | 461 | 18.8 | 2878 | 20.0 |
| 50–59 | 611 | 25.0 | 3554 | 24.7 |
| 60–69 | 618 | 25.2 | 3646 | 25.3 |
| 70+ | 667 | 27.2 | 3811 | 26.5 |
| Length of enrollment | ||||
| 4–9 | 642 | 26.2 | 3781 | 26.3 |
| 10–19 | 1007 | 41.1 | 5900 | 41.0 |
| 20+ years | 800 | 32.7 | 4715 | 32.8 |
| First degree family history of breast cancer | ||||
| Yes | 452 | 20.6 | 1697 | 13.5 |
| No | 1746 | 79.4 | 10833 | 86.5 |
| Missing | 251 | (10.3) | 1866 | (13.0) |
| Age at menarche | ||||
| ⩽10 | 141 | 6.0 | 740 | 5.6 |
| 11–14 | 1936 | 83.0 | 10879 | 82.5 |
| 15+ | 256 | 11.0 | 1566 | 11.9 |
| Missing | 116 | (4.7) | 1211 | (8.4) |
| Parous | ||||
| Yes | 1910 | 85.9 | 11037 | 87.6 |
| No | 314 | 14.1 | 1568 | 12.4 |
| Missing | 225 | (9.2) | 1791 | (12.4) |
| Age at first birth (among parous women) | ||||
| <20 | 374 | 19.6 | 2174 | 19.7 |
| 20–24 | 816 | 42.7 | 4804 | 43.5 |
| 25–29 | 443 | 23.2 | 2709 | 24.6 |
| 30–34 | 218 | 11.4 | 970 | 8.8 |
| 35+ | 58 | 3.0 | 377 | 3.4 |
| Missing | 1 | (0.05) | 4 | (0.04) |
| Use of birth control pills | ||||
| Yes | 1131 | 53.8 | 6301 | 52.0 |
| No | 973 | 49.7 | 5821 | 48.0 |
| Missing | 345 | (14.1) | 2274 | (15.8) |
| Ever use of HRT | ||||
| Yes | 1095 | 50.3 | 5352 | 43.8 |
| No | 1083 | 49.7 | 6858 | 56.3 |
| Missing | 271 | (11.1) | 2186 | (15.2) |
| Duration of use of HRT | ||||
| ⩾5 years | 632 | 29.0 | 2901 | 23.8 |
| < 5 years | 443 | 20.3 | 2348 | 19.2 |
| Duration unknown | 20 | 0.9 | 103 | 0.8 |
| None | 1083 | 49.7 | 6858 | 56.2 |
| Missing | 271 | (11.1) | 2186 | (15.2) |
| Body mass index | ||||
| Normal (<25) | 1005 | 46.0 | 6101 | 49.7 |
| Overweight (25–29.9) | 665 | 30.4 | 3536 | 28.8 |
| Obese (30+) | 516 | 23.6 | 2631 | 21.5 |
| Missing | 263 | (10.7) | 2128 | (14.8) |
| Race | ||||
| White | 1859 | 90.8 | 9768 | 89.1 |
| Asian | 87 | 4.3 | 568 | 5.2 |
| Black | 57 | 2.8 | 351 | 3.2 |
| Multi/other | 44 | 2.2 | 275 | 2.5 |
| Missing | 402 | (16.4) | 3434 | (23.9) |
| Education | ||||
| Less than high school | 143 | 6.7 | 792 | 7.2 |
| High school graduate | 499 | 23.3 | 2627 | 23.8 |
| Some post secondary | 736 | 34.3 | 3851 | 34.9 |
| College graduate | 350 | 16.3 | 1687 | 15.3 |
| Advanced degree/some graduate school | 418 | 19.5 | 2094 | 19.0 |
| Missing | 303 | (12.4) | 3345 | (23.2) |
| Previous biopsy | ||||
| Yes | 574 | 25.9 | 2156 | 17.2 |
| No | 1640 | 74.1 | 10406 | 82.8 |
| Missing | 235 | (9.6) | 1834 | (12.7) |
| At least 1 screening mammogram within 2 years prior to reference date | ||||
| Yes | 1728 | 70.6 | 8370 | 58.1 |
| No | 721 | 29.4 | 6026 | 41.9 |