Table 3

Predictors of stromal proportion among all women, controlling for variables relating to parity, and among parous women only

A. All womenFull modelar2 = 0.23Parsimonious modelar2 = 0.22
PredictorsβPβP
Age at biopsy (years)−0.070.74−0.080.68
Menopause (pre/post)−4.090.17−4.040.16
Proliferative without atypia (yes/no)4.980.045.110.03
Atypical hyperplasia (yes/no)4.820.214.710.23
Oral contraceptive use (ever/never)−5.930.01−5.800.01
Family history (yes/no)−1.280.67
Age at menarche (years)1.410.16
BMI (weight/height2)−0.450.09−0.500.05
Height in 1976 (inches)−0.630.16−0.580.19
B. Parous women onlyFull modelb r2 = 0.22Parsimonious modelc
Predictorsβ P β P
Time since last birth (years)−0.390.30
Age at first birth (years)−0.070.83
Parity (1–9)−0.300.80
History of breast feeding (yes/no)1.060.70
  • a Controlling for combined term including parity (0, 1–2, >2), age at first birth (≤24, 25–29, >30 years), and time since last birth in single years.

  • b Controlling for age at biopsy (years), menopausal status, (pre-, post-, missing), interaction between age and menopause, categories of benign breast disease (nonproliferative, proliferative, and atypical hyperplasia), use of oral contraceptives (ever/never), family history (yes/no), age at menarche (years), BMI (weight/height2), and height (inches).

  • c None of the parity-related variables met the criteria for inclusion in the parsimonious model.