Table 3 Examples of established nongenetic risk factors.
| Factor | Comparator | OR*/HR**/RR*** (95 % CI) | Remark | Reference |
|---|---|---|---|---|
| CI: confidence intervals; HR: hazard ratio; HRT: hormone replacement therapy; OR: odds ratio; RR: relative risk. | ||||
| Estrogen + progestin HRT | no HRT | 1.25** (1.07–1.46) | 33 | |
| Birth | one child less | 0.93* (0.91–0.97 | risk reduction per child | 25 |
| 12 monthsʼ breastfeeding | 12 months less breastfeeding | 0.96* (0.94–0.97) | risk reduction per 12 monthsʼ breastfeeding | 25 |
| First-degree relative with breast cancer | no first-degree relative with breast cancer | 1.78***–2.61*** (CI not reported) | figures from the BCDDP and the Nursesʼ Health Study | 118 |
| History of breast biopsy | no history of breast biopsy | 1.9*** (1.2–2.9) | 119 | |
| History of atypical breast biopsy | no history of atypical breast biopsy | 5.3*** (3.1–8.8) | 119 | |
| Age at menarche > 14 | age at menarche < 12 | *0.77 (CI not reported) | 120, 121, 122 | |
| Age at menopause < 45 | age at menopause > 54 | 2.0* (CI not reported) | 120, 121, 122 | |