Table 2

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

A. All womenFull modelar2 = 0.21Parsimonious modelar2 = 0.20
Age at biopsy (years)−0.040.32−0.030.41
Menopausal (yes/no)b−1.580.01−1.560.01
Proliferative without atypia (yes/no)1.81<0.0011.80<0.001
Atypical hyperplasia (yes/no)
Oral contraceptive use (ever/never)−0.430.30
Family history (yes/no)0.720.25
Age at menarche (years)0.090.63
BMI (weight/height2)−0.0030.96
Height in 1976 (inches)−0.060.48
B. Parous women onlyFull modelcr2 = 0.29Parsimonious model r2 = 0.24
Predictorsβ P β P
Time since last birth (years)
 Premenopausal women−0.31<0.001−0.26<0.001
 Postmenopausal women−0.090.20−0.080.13
Age at first birth (years)−0.010.80
Parity (0–9)−0.060.76
History of breast feeding (yes/no)0.500.29
  • a Controlling for cross-classified term including parity (0, 1–2, >2), age at first birth (≤24, 25–29, >30 years), and time since last birth in single years and a missing indicator term.

  • b From a model with missing menopausal status excluded, controlling for other covariates.

  • c Also controlling for menopausal status (pre-, post-, missing), interaction between menopausal status and time since last birth (continuous), categories of benign breast disease (nonproliferative, proliferative, and atypical hyperplasia), family history (yes/no), age at biopsy (years), oral contraceptive use (ever, never, missing), BMI (weight/height2), and height (inches).