Table 4.
Relative risks and 95% confidence intervals for Breast Cancer Risk Assessment Tool risk factors from BCDDP, NHS, and WHI-ES
| Risk factors | BCDDP* | NHS*,† | WHI-ES*,† | NHS*,† | WHI-ES*,† | NHS*,† | WHI-ES*,† |
|---|---|---|---|---|---|---|---|
| Overall | Overall | Overall | 55–74 y‡ | 55–74 y | 75+ y | 75+ y | |
| (n = 71 293) | (n = 79 611) | (n = 52 111) | (n = 57 009) | (n = 19 182) | (n = 22 602) | ||
| Age at menarche, y | |||||||
| ≤11, % | 1.21 | 1.27 (1.07 to 1.50) |
1.08 (0.93 to 1.25) |
1.38 (1.14 to 1.68) |
1.02 (0.86 to 1.21) |
0.99 (0.72 to 1.37) |
1.22 (0.92 to 1.62) |
| 12–13, % | 1.10 | 1.13 (1.04 to 1.22) |
1.04 (0.96 to 1.12) |
1.17 (1.07 to 1.30) |
1.01 (0.93 to 1.10) |
0.99 (0.85 to 1.17) |
1.10 (0.96 to 1.27) |
| ≥14, % | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Age at first birth, y X 0,1,2+ first degree relatives | |||||||
| ≤19 and 0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| ≤19 and 1 | 2.61 | 1.46 (1.12 to 1.91) |
1.48 (1.21 to 1.81) |
1.33 (0.96 to 1.84) |
1.47 (1.15 to 1.86) |
1.87 (1.16 to 3.00) |
1.50 (1.01 to 2.22) |
| ≤19 and 2+ | 6.80 | 2.13 (1.25 to 3.64) |
2.18 (1.45 to 3.29) |
1.77 (0.92 to 3.40) |
2.15 (1.33 to 3.48) |
3.50 (1.35, 9.02) |
2.24 (1.02 to 4.91) |
| 20–24 and 0 | 1.24 | 1.11 (1.01 to 1.22) |
1.13 (1.06 to 1.21) |
1.13 (1.02 to 1.26) |
1.14 (1.06 to 1.23) |
1.09 (0.91 to 1.30) |
1.12 (0.98 to 1.27) |
| 20–24 and 1 | 2.68 | 1.58 (1.30 to 1.90) |
1.67 (1.44 to 1.92) |
1.51 (1.21 to 1.89) |
1.71 (1.44 to 2.01) |
1.82 (1.26 to 2.62) |
1.61 (1.22 to 2.14) |
| 20–24 and 2+ | 5.78 | 2.24 (1.63 to 3.07) |
2.45 (1.91 to 3.16) |
2.01 (1.38 to 2.94) |
2.54 (1.89 to 3.42) |
3.05 (1.67 to 5.56) |
2.33 (1.42 to 3.80) |
| 25–29/nulliparous§ and 0 | 1.55 | 1.23 (1.03 to 1.48) |
1.28 (1.13 to 1.46) |
1.28 (1.03 to 1.59) |
1.31 (1.12 to 1.52) |
1.18 (0.83 to 1.69) |
1.25 (0.97 to 1.60) |
| 25–29/nulliparous and 1 | 2.76 | 1.70 (1.40 to 2.06) |
1.88 (1.61 to 2.20) |
1.71 (1.36 to 2.16) |
1.98 (1.64 to 2.40) |
1.77 (1.22 to 2.58) |
1.74 (1.29 to 2.33) |
| 25–29/nulliparous and 2+ | 4.91 | 2.34 (1.80 to 3.05) |
2.75 (2.13 to 3.56) |
2.29 (1.65 to 3.18) |
3.00 (2.19 to 4.12) |
2.65 (1.65 to 4.27) |
2.41 (1.54 to 3.78) |
| ≥30 and 0 | 1.93 | 1.37 (1.04 to 1.80) |
1.46 (1.20 to 1.77) |
1.46 (1.05 to 2.01) |
1.49 (1.19 to 1.88) |
1.29 (0.75 to 2.20) |
1.40 (0.96 to 2.04) |
| ≥30 and 1 | 2.83 | 1.83 (1.39 to 2.41) |
2.12 (1.68 to 2.68) |
1.95 (1.38 to 2.75) |
2.30 (1.72 to 3.07) |
1.72 (1.04 to 2.85) |
1.87 (1.23 to 2.85) |
| ≥30 and 2+ | 4.17 | 2.46 (1.59 to 3.79) |
3.09 (2.04 to 4.68) |
2.60 (1.47 to 4.60) |
3.55 (2.11 to 5.96) |
2.31 (1.14 to 4.67) |
2.51 (1.23 to 5.09) |
| No. of biopsies | |||||||
| 0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| 1 | 1.27 | 1.32 (1.21 to 1.45) |
1.27 (1.19 to 1.36) |
1.33 (1.20 to 1.48) |
1.25 (1.15 to 1.35) |
1.29 (1.07 to 1.57) |
1.33 (1.18 to 1.50) |
| 2+ | 1.62 | 1.75 (1.45 to 2.10) |
1.61 (1.41 to 1.84) |
1.77 (1.43 to 2.18) |
1.55 (1.33 to 1.82) |
1.67 (1.13 to 2.46) |
1.77 (1.38 to 2.26) |
* Nurses’ Health Study began in 2004. Women’s Health Initiative Extension Study began in 2005. BCDDP = Breast Cancer Demonstration and Detection Project (31); CI = confidence interval; NHS = Nurses’ Health Study; RR = relative risk; WHI-ES = Women’s Health Initiative Extension Study.
† The relative risks for Gail model risk factors were estimated from logistic regression models. The Gail model treated each variable (as it is categorized) as continuous in its model.
‡ The youngest women in NHS in 2004 were age 57 years.
§ No separate indicator was used for nulliparous women.