| Risk group | |||
| Low risk | High risk | Relative risk | |
| Risk factors | |||
| Deleterious BRCA1/BRCA2 genes | Negative | Positive | 3.0 to 7.0 |
| Mother or sister with breast cancer | No | Yes | 2.6 |
| Age | 30 to 34 | 70 to 74 | 18.0 |
| Age at menarche | >14 | <12 | 1.5 |
| Age at first birth | <20 | >30 | 1.9 to 3.5 |
| Age at menopause | <45 | >55 | 2.0 |
| Use of contraceptive pills | Never | Past/current use | 1.07 to 1.2 |
| Hormone replacement therapy (estrogen + progestin) | Never | Current | 1.2 |
| Alcohol | None | 2 to 5 drinks/day | 1.4 |
| Breast density on mammography (percents) | 0 | ≥75 | 1.8 to 6.0 |
| Bone density | Lowest quartile | Highest quartile | 2.7 to 3.5 |
| History of a benign breast biopsy | No | Yes | 1.7 |
| History of atypical hyperplasia on biopsy | No | Yes | 3.7 |
| Protective factors | |||
| Breast feeding (months) | ≥16 | 0 | 0.73 |
| Parity | ≥5 | 0 | 0.71 |
| Recreational exercise | Yes | No | 0.70 |
| Postmenopause body mass index (kg/m2) | <22.9 | >30.7 | 0.63 |
| Oophorectomy before age 35 years | Yes | No | 0.3 |
| Aspirin | ≥Once/week for ≥6 months | Nonusers | 0.79 |
