Table 5.

Multivariate relative risk estimates for all available risk factors

Age-adjusted multivariate relative risk (95% CI)
Premenopausal women (n = 23,970)Postmenopausal women (n = 32,607)
Family history of breast cancer
    No1.001.00
    Yes1.65 (1.30–2.10)1.40 (1.19–1.65)
Age at first childbirth
    <211.001.00
    21–301.03 (0.75–1.42)1.16 (0.97–1.39)
    >301.76 (1.22–2.54)1.52 (1.12–2.06)
    No children1.46 (1.02–2.09)1.45 (1.14–1.85)
Postmenopausal hormone use
    Never or formerly used1.00
    Currently using1.31 (1.13–1.53)
BMI (kg/m2)
    <22.01.001.00
    22.0–24.90.73 (0.55–0.97)1.17 (0.93–1.47)
    25.0–27.40.82 (0.58–1.16)1.23 (0.96–1.57)
    27.5–29.90.85 (0.56–1.29)1.41 (1.08–1.84)
    ≥300.92 (0.65–1.30)1.56 (1.23–1.98)
Breast density
    Entirely fat1.001.00
    Scattered2.50 (0.92–6.82)2.06 (1.47–2.89)
    Heterogeneous3.62 (1.32–9.92)2.75 (1.93–3.92)
    Extremely4.21 (1.49–11.80)3.48 (2.24–5.40)