Table 1.

Selected characteristics of subjects

Characteristics (N = 1,114 case-control pairs)Case*ControlP
Age (y)56.7 (9.1)56.7 (9.1)
Height (cm)162.3 (6.6)162.3 (6.7)0.97
Weight (kg)65.7 (11.5)65.6 (11.3)0.81
BMI25.0 (4.2)24.9 (4.2)0.91
Age at menarche (y)12.9 (1.5)13.0 (1.5)0.05
n = 1,084n = 1,090
Age at first birth (y)24.8 (4.7)24.3 (4.4)0.05
n = 932n = 981
Parity (% parous)84.288.40.004
Number of live births2.5 (1.8)2.7 (1.8)<0.001
n = 1,113
Postmenopausal (%)74.776.00.46
    Natural menopause42.645.0
    Surgical menopause32.131.1
Age at menopause (y)50.99 (50.94-51.04)50.92 (50.85-50.99)0.03
n = 992n = 998
Hormone replacement therapy (% ever use)35.732.50.11
Years of hormone replacement therapy use2.4 (5.6)2.1 (5.4)0.07
n = 1,096n = 1,092
Breast cancer in first degree relative (%)<0.001
    079.484.4
    118.014.4
    2+2.61.3
Percent density32.7 (19.7)26.9 (19.1)<0.001
  • * Data shown is mean (SD) for continuous variables (except age at menopause), percentage for categorical variables.

  • P values for age at menopause is based on log-rank test, for symmetrically distributed variable is based on paired t test, for nonsymmetrically distributed variable is based on Wilcoxon rank sum test, and for categorical variable is based on Mantel-Haenszel χ2 test. All statistical tests are two-sided.

  • Median age at menopause and 95% CI from Kaplan-Meier estimates.