Table 1.
Relative Risk Estimates for Breast Cancer in the Black Women's Health Study, 1995 to 2005
| Risk Factor | No. of Breast Cancers | No. of Person-Years | RR* | 95% CI |
|---|---|---|---|---|
| Family history | ||||
| None | 598 | 362,263 | 1.00 | Reference |
| First-degree relative diagnosed at age < 50 years | 77 | 19,288 | 2.24 | 1.76 to 2.84 |
| First-degree relative diagnosed at age ≥ 50 years | 76 | 24,421 | 1.53 | 1.20 to 1.94 |
| Second-degree relative | 145 | 66,008 | 1.35 | 1.12 to 1.62 |
| Benign breast disease/biopsy | ||||
| No | 598 | 372,449 | 1.00 | Reference |
| Yes | 298 | 99,530 | 1.45 | 1.25 to 1.67 |
| Body mass index at age 18 years, kg/m2 | ||||
| < 20 | 442 | 197,739 | 1.50 | 1.17 to 1.92 |
| 20-24 | 378 | 210,802 | 1.31 | 1.02 to 1.68 |
| ≥ 25 | 76 | 63,438 | 1.00 | Reference |
| Age at menarche, years | ||||
| < 12 | 273 | 132,548 | 1.42 | 1.16 to 1.73 |
| 12-13 | 472 | 246,749 | 1.24 | 1.03 to 1.50 |
| ≥ 14 | 151 | 92,683 | 1.00 | Reference |
| Age at first birth, years | ||||
| Nulliparous or < 25 | 635 | 356,859 | 1.00 | Reference |
| ≥ 25 | 261 | 115,120 | 1.32 | 1.14 to 1.53 |
| Oral contraceptive use | ||||
| < 10 years in duration and ≥ 10 years ago | 663 | 312,506 | 1.00 | Reference |
| ≥ 10 years in duration or < 10 years ago | 233 | 159,474 | 1.19 | 1.01 to 1.41 |
| Bilateral oophorectomy | ||||
| No | 793 | 422,531 | 1.46 | 1.18 to 1.80 |
| Yes | 103 | 49,449 | 1.00 | Reference |
| Estrogen plus progestin use, years | ||||
| < 3 | 838 | 459,197 | 1.00 | Reference |
| ≥ 3 | 58 | 12,782 | 1.33 | 1.01 to 1.76 |
| Height | ||||
| < 5 feet, 5 inches | 384 | 213,182 | 1.00 | Reference |
| ≥ 5 feet, 5 inches | 512 | 258,798 | 1.15 | 1.01 to 1.32 |
Abbreviation: RR, relative risk.
*
Adjusted for age and all risk factors in the table.