Table 1 Basic characteristics of the study population (n = 775)

Height (cm)

163.7 (6.1)

Weight (kg)

69.7 (11.7)

Body mass index (kg/m²)

26.0 (4.1)

Waist–hip ratio

0.79 (0.06)

Family history of breast cancer (mother and/or sister with history of breast cancer)

106 (13.7)^a

Reproductive factors

   Age at menarche (years)

13.5 (1.7)

   Nulliparous

99 (12.8)^a

   Age at first child birth(years) (among parous women only)

25.4 (4.0)

   Number of children (average) (among parous women only)

2.6 (0.9)

   Ever breast feeding(among parous women only)

558 (82.5)^a

   Age at menopause (years)

48.8 (4.9)

   Time since menopause (years)

11.2 (6.8)

Lifestyle factors

   Ever used oral contraceptives

416 (53.7)^a

   Ever used hormone therapy

112 (14.4)^a

   Time since stopped hormone therapy use (years) (among former hormone therapy users only)

7.1 (6.4)

   Current smoking

171 (22.1)^a

   Ever smoked

421 (54.3)^a

   Alcohol intake (g/day)

8.1 (11.2)

Sex steroids and sex hormone binding globulin

   Oestrone (pg/ml)

15.26 (4.38–53.16)^b

   Oestradiol (pg/ml)

8.22 (2.92–23.17)^b

   Free oestradiol (pg/ml)

0.24 (0.09–0.73)^b

   Dehydroepiandrosterone sulfate (ng/ml)

446.7 (102.3–1,949.8)^b

   Androstenedione (ng/ml)

0.46 (0.10–2.11)^b

   Testosterone (ng/ml)

0.25 (0.09–0.72)^b

   Free testosterone (pg/ml)

5.30 (1.46–19.23)^b

   Sex hormone binding globulin (nmol/l)

19.63 (5.21–73.96)^b

Breast measures

   Percentage breast density

21.7 (14.9–30.8)^c

   Dense area

25.3 (18.4–35.5)^c

   Nondense area

95.1 (70.1–121.9)^c