Table 1.

Baseline characteristics of the 7,676 subjects

CharacteristicMean (SD)
P
Invasive ER+ breast cancer (n = 208)No breast cancer (n = 7,468)
Age (y)70.3 (4.3)71.9 (5.4)<0.001*
Education (y)12.9 (2.7)12.4 (2.8)0.01*
Weight (kg)70.9 (12.8)67.3 (12.6)<0.001*
Age at menarche (y)12.9 (1.5)13.1 (1.5)0.22
Age at last natural menses (y)47.7 (5.8)47.0 (6.3)0.13
Years of reproductive life (y)34.7 (6.1)34.0 (6.5)0.16
Age at first childbirth (y)25.4 (5.2)25.3 (4.9)0.74
No. live births2.8 (1.7)2.7 (1.6)0.61
No. children breast-fed1.6 (1.6)1.6 (1.6)0.60
Underwent surgical menopause (%)11.49.80.46
Past use of estrogen therapy (%)35.031.80.33
Family history of breast cancer (%)16.214.50.51
Current smoker (%)11.110.00.62
Alcoholic drinks per week2.4 (4.8)1.9 (4.1)0.07
Physical activity (total weekly kcal in past year)1,711 (1,792)1,552 (1,627)0.17
Takes walks for exercise (%)47.649.10.66
Distal radius BMD (g/cm2)0.38 (0.08)0.35 (0.08)<0.001*
Lumbar spine BMD (g/cm2)0.88 (0.15)0.84 (0.16)0.01*
Total hip BMD (g/cm2)0.79 (0.12)0.75 (0.13)<0.001*
  • Abbreviation: BMD, bone mineral density.

  • * Significant difference at P < 0.05 using two-sided t test.

  • Having a mother or sister with breast cancer.