Table 1.

Characteristics of the study population by ethnicity

VariablesAsian (n = 85)Caucasian (n = 83)Mixed (n = 52)P*
Age (years)43.5 (42.9-44.1)42.9 (42.3-43.5)42.4 (41.6-43.2)0.11
BMI (kg/m2)24.6 (23.5-25.6)25.8 (24.7-26.9)26.7 (25.3-28.2)0.048
Family history of breast cancer (%)11.017.115.70.52
Age at menarche before 13 (%)60.051.867.30.19
Number of children (%)17.3
    none23.534.917.3
    one to two57.744.651.90.10
    three or more18.820.530.9
Estrogen levels in serum (means of multiple measurements over 2 years)
    E1 (pg/mL)84.7 (77.5-92.7)86.6 (79.0-95.0)91.5 (81.7-102.6)0.56
    E2 (pg/mL)129.0 (118.1-140.9)135.1 (123.5-147.9)141.4 (126.3-158.2)0.58
Urinary estrogens and their metabolites (measured once at baseline)
    E1 (ng/mg creatinine)8.7 (7.2-10.4)9.4 (7.8-1.2)9.1 (7.2-11.4)0.83
    E2 (ng/mg creatinine)3.7 (3.2-4.3)3.6 (3.1-4.2)3.7 (3.1-4.4)0.97
    2-OHE1 (ng/mg creatinine)20.2 (17.2-23.7)27.1 (23.2-31.7)18.6 (15.3-22.6)0.006
    16α-OHE1 (ng/mg creatinine)15.0 (13.0-17.4)14.4 (12.5-16.5)12.9 (10.8-15.4)0.42
    2-OHE1/16α-OHE1 ratio1.35 (1.19-1.54)1.89 (1.66-2.15)1.51 (1.28-1.78)0.008
Variant allele frequencies
    COMT 158Met0.250.570.22<0.0001
    CYP1A1*2A0.440.130.41<0.0001
    CYP1A1*2B0.300.070.23<0.0001
    CYP1A2*1F0.270.220.270.07
    CYP1B1 432Leu0.190.460.33<0.0001
    CYP17 27C0.480.350.390.10
  • NOTE: The values are means for age and geometric means [95% confidence intervals (CI)] for other variables, except when indicated.

  • * P values from ANOVA for continuous variables and from χ2 test for categorical variables.