Table 1.

Characteristics and hormone levels of subjects at baseline (cases and subcohort)

Breast cancer cases* (N = 423)Subcohort (N = 1,901)
Age at baseline, years; mean ± SD (range)56 ± 9 (39-70)55 ± 9 (36-70)
Country of birth, n (%)
    Australia/New Zealand324 (76.6)1,318 (69.3)
    United Kingdom14 (3.3)127 (6.7)
    Italy47 (11.1)257 (13.5)
    Greece38 (9.0)199 (10.5)
Age at menarche (years), n (%)
    <1273 (17.3)309 (16.3)
    1268 (16.1)386 (20.3)
    13112 (26.5)507 (26.7)
    14+168 (39.7)695 (36.6)
Parity (age at first pregnancy and number of full-term pregnancies), n (%)
    Nulliparous74 (17.5)261 (13.7)
    <25 and 110 (2.4)46 (2.4)
    <25 and >1166 (39.2)829 (43.6)
    ≥25 and 126 (6.1)131 (6.9)
    ≥25 and >1146 (34.5)632 (33.2)
Duration of lactation, n (%)
    Never145 (34.3)543 (28.6)
    Up to 6 mo74 (17.5)385 (20.3)
    7-12 mo64 (15.1)311 (16.4)
    13-24 mo79 (18.7)346 (18.2)
    >24 mo52 (12.3)291 (15.3)
Oral contraceptive use, n (%)
    Never195 (46.1)806 (42.4)
    Past or current227 (53.7)1,093 (57.5)
Menopausal status, n (%)
    Premenopausal166 (39.2)769 (40.5)
    Postmenopausal257 (60.8)1,132 (59.5)
Hormone replacement therapy use, n (%)
    Never376 (88.9)1,690 (88.9)
    Past41 (9.7)191 (10.0)
Physical activity, n (%)
    None82 (19.4)425 (22.4)
    Low99 (23.4)394 (20.7)
    Medium161 (38.1)676 (35.6)
    High81 (19.1)406 (21.4)
BMI, kg/m2; n (%)
    <25159 (37.6)767 (40.4)
    25-29160 (37.8)707 (37.2)
    30+104 (24.6)426 (22.4)
Alcohol consumption, n (%)
    Abstainers163 (38.5)766 (40.3)
    Ex-drinkers14 (3.3)77 (4.1)
    1-19 g/d205 (48.5)858 (45.1)
    20-39 g/d26 (6.1)157 (8.3)
    ≥40 g/d15 (3.5)42 (2.2)
Energy from diet, kJ/d; mean (SD)8,463 (2,851)8,510 (2,789)
Smoking, n (%)
    Never316 (74.7)1,321 (69.5)
    Past77 (18.2)406 (21.4)
    Current30 (7.1)174 (9.2)
Education, n (%)
    Primary school79 (18.7)400 (21.0)
    Some high school183 (43.3)797 (41.9)
    Completed high school84 (19.9)348 (18.3)
    Degree/diploma77 (18.2)356 (18.7)
IGF-I, nmol/L; geometric mean (95% CI)21.1 (20.4-21.9)21.0 (20.6-21.3)
IGFBP-3, nmol/L; geometric mean (95% CI)111.6 (109.2-114.0)110.1 (109.0-111.3)
  • NOTE: Percentages do not always sum up to 100% because of missing values.

  • * Forty breast cancer cases were also included in the subcohort.