Table 2.

Characteristics of subjects

CharacteristicsMean or % (95% CI)
Age at mammogram (y)55.3 (54.9–55.6)
Physical
    Weight (kg)69.1 (68.5–69.7)
    Height (cm)162.6 (162.4–162.9)
    BMI (kg/m2)26.2 (25.9–26.4)
Reproductive variables
    Age at menarche (y)13.07 (13.01–13.14)
    Parous (%)86.8 (85.3–88.2)
    No. of live births2.33 (2.28–2.39)
    Postmenopausal (%)69.7 (67.7–71.5)
Oral contraceptives
    Ever use of oral contraceptive (%)86.6 (85.1–88.0)
    Current use of oral contraceptive (%)5.6 (4.7–6.7)
    Years of oral contraceptive use (n = 2,050)7.6 (7.3–7.9)
HRT
    Ever use of HRT (%)39.6 (37.6–41.6)
    Current use of HRT (%)14.2 (12.7–15.6)
    Years of HRT use (n = 906)6.3 (5.9–6.7)
Smoking
    Ever smoked (%)36.1 (34.2–38.2)
    Current smoker (%)9.1 (7.9–10.3)
    Years of smoking (n = 827)17.8 (16.9–18.7)
Alcohol
    Ever drank alcohol (%)59.4 (57.4–61.5)
    Years of drinking (n = 1,417)22.7 (22.1–23.3)
Mammographic density measures
    Percent dense area (%)25.26 (24.56–25.95)
    Square root dense area (cm)4.98 (4.90–5.06)
    Square root nondense area (cm)9.60 (9.49–9.71)

Abbreviation: HRT, hormone replacement therapy.