Table 2.

Geometric means of absolute density, absolute nondensity and relative density and trend tests over groups of characteristics

nAbsolute dense, cm2Absolute nondense, cm2Percent dense, %
Age at examination, y
    P for trend418<0.01<0.01<0.01
Weight, kg
    P for trend4180.06<0.01<0.01
Height, m
    P for trend4180.150.510.18
BMI, kg/m2
    20 to <2518726.662.026.4
    25 to <3017121.6101.115.8
    P for trend4180.07<0.01<0.01
Age at menarche, y
    P for trend4160.160.070.08
Age at menopause, y
    P for trend3610.010.420.04
Time since menopause, y
    P for trend361<0.01<0.01<0.01
Age at first childbirth, y
    P for trend3320.420.700.50
Parity (no. children)
    P for trend418<0.01<0.01<0.01
Current oral contraceptive use
Ever used oral contraceptives
Used hormone therapy in the last 12 mo
Ever smoked
Family history of breast cancer*
  • NOTE: Geometric means were calculated in tertiles of continuous variables or binary groups of dichotomous variables. For BMI, standard classes were used and for parity, nominal classes were used, with a truncation at >3. Tests for linear trends were done through ANOVA with an F test on the geometric data.

  • * Defined as one or more affected mother and/or sister.