Table 1.

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

Breast cancer cases*Subcohort
n = 197n = 857
Age, y; mean, SD (range)62, 5 (48-70)61, 6 (46-70)
Country of birth, n (%)Australia/New Zealand144 (73.1)569 (66.4)
United Kingdom9 (4.6)47 (5.5)
Italy26 (13.2)134 (15.6)
Greece18 (9.1)107 (12.5)
Age at menarche, n (%)Less than 12 y27 (13.7)109 (12.7)
12 y35 (17.8)160 (18.7)
13 y56 (28.4)217 (25.3)
14 y or more79 (40.1)371 (43.3)
Parity and age at first pregnancy (live birth or gestation >24 wk), n (%)Nulliparous30 (15.2)100 (11.7)
1 and <255 (2.5)15 (1.8)
>1 and <2575 (38.1)358 (41.8)
1 and ≥2511 (5.6)52 (6.1)
>1 and ≥2576 (38.6)332 (38.7)
Lactation, n (%)Never63 (32.0)214 (25.0)
Up to 6 mo35 (17.8)184 (21.5)
7-12 mo32 (16.2)147 (17.2)
13-24 mo43 (21.8)173 (20.2)
>24 mo24 (12.2)139 (16.2)
Oral contraceptive use, n (%)Never user123 (62.4)492 (57.4)
Past user74 (37.6)365 (42.6)
HRT use, n(%)Never user174 (88.3)760 (88.7)
Past user23 (11.7)97 (11.3)
Physical activity, n (%)None38 (19.3)182 (21.2)
Low45 (22.8)176 (20.5)
Medium78 (39.6)341 (39.8)
High36 (18.3)158 (18.4)
Alcohol, n (%)Abstainers89 (45.2)403 (47.0)
Exdrinkers6 (3.0)31 (3.6)
1-19 g/d82 (41.6)339 (39.6)
20-39 g/d14 (7.1)69 (8.1)
40 g/d or more6 (3.0)15 (1.8)
Smoking, n (%)Never150 (76.1)612 (71.4)
Current11 (5.6)74 (8.6)
Past36 (18.3)171 (20.0)
Education, n (%)Primary school46 (23.4)247 (28.8)
Some high school98 (49.7)378 (44.1)
Completed high school33 (16.8)130 (15.2)
Degree/diploma20 (10.2)102 (11.9)
BMI (kg/m2); mean, SD27.7, 4.727.3, 4.7
Energy from diet (MJ/d); mean, SD8.3, 2.78.5, 2.9
Hormones and SHBG, median (interquartile range)
Total estradiol (pmol/L)57.00 (46.00-74.00)57.00 (45.35-71.00)
Free estradiol (pmol/L)0.87 (0.63-1.13)0.80 (0.60-1.05)
Estrone sulfate (nmol/L)3.22 (2.29-4.41)2.95 (2.15-4.03)
Testosterone (nmol/L)0.70 (0.50-1.10)0.70 (0.50-1.10)
DHEAS (μmol/L)1.50 (1.00-2.30)1.50 (0.90-2.40)
Androstenedione (nmol/L)2.19 (1.60-3.17)2.16 (1.41-3.06)
SHBG (nmol/L)43.10 (32.90-57.30)51.10 (38.55-67.80)
  • *Nineteen breast cancer cases were also in the subcohort.

  • The number of missing measures among cases and in the subcohort were as follows: 2 and 15 for total estradiol, 2 and 16 for free estradiol, 5 and 16 for estrone sulfate, 1 and 4 for testosterone, 0 and 3 for DHEAS, 1 and 3 for androstenedione, 0 and 1 for SHBG.