Table 1.

Characteristics of the study population

Premenopausal women (n = 783)*Postmenopausal women (n = 791)
Age (y), mean (SD)46.8 (4.6)61.4 (6.8)
Age at menarche (y), mean (SD)12.8 (1.6)12.7 (1.6)
Age at first full-term pregnancy (y), mean (SD)26.3 (4.2)25.2 (4.1)
No. full-term pregnancies, mean (SD)1.6 (1.1)2.1 (1.8)
BMI (kg/m2), mean (SD)25.2 (4.6)27.1 (4.7)
WHR, mean (SD)0.78 (0.06)0.81 (0.06)
Weight (kg), mean (SD)65.0 (12.1)67.3 (11.9)
Height (cm), mean (SD)160.5 (5.8)157.6 (5.6)
Waist circumference (cm), mean (SD)79.7 (10.8)85.2 (11.3)
Hip circumference (cm), mean (SD)101.6 (8.9)104.8 (9.4)
Physical activity (metabolic equivalents-hour/wk), mean (SD)26.9 (22.2)25.7 (23.4)
Energy intake (kcal/d), mean (SD)1,912 (521)1,978 (669)
Alcohol intake (drinks/wk), mean (SD)3.4 (3.8)2.5 (4.4)
Parity (parous), %75.474.8
Lactation (yes), %62.228.8
Use of hormonal derivatives (ever),§ %91.870.3
Family history of breast cancer in first-degree relative (yes), %37.130.7
History of breast biopsies (yes), %14.416.1
Smoking status (never), %45.559.0
Education (college or university diploma), %62.139.2
Breast density (%), median (range)41.2 (0.1-92.9)13.6 (0-82)
Dense region (cm2), median (range)43.6 (0.1-163.7)18.1 (0-180.8)
Nondense region (cm2), median (range)64.0 (5.3-360.1)116.6 (11.0-453.8)
Total region (cm2), median (range)114.4 (34.2-389.2)138.8 (34.5-456.5)
IGF-I (ng/mL), median (range)218.0 (65.6-501.1)184.3 (42.2-511.7)
IGFBP-3 (ng/mL), median (range)4,696 (2,643-8,451)4,806 (2,126-9,581)
IGF-I/IGFBP-3 molar ratio, median (range)0.17 (0.05-0.33)0.14 (0.05-0.33)
  • * Missing values for age at menarche (n = 19), physical activity (n = 1), energy intake (n = 6), alcohol intake (n = 4), family history of breast cancer in first-degree relative (n = 7), and education (n = 1).

  • Missing values for age at menarche (n = 21), WHR (n = 4), waist (n = 3), hip (n = 4), physical activity (n = 2), energy intake (n = 5), alcohol intake (n = 3), lactation (n = 2), family history of breast cancer in first-degree relative (n = 8), and education (n = 1).

  • Among parous women.

  • § Contraceptives and/or replacement therapy.