Mean age (SD), y | 44.4 (4.8) | 44.3 (4.8) |

Mean age at diagnosis (SD), y | 54.4 (6.5) | — |

Mean age at menarche (SD), y | 12.5 (1.5) | 12.4 (1.5) |

Mean age at first full-term pregnancy^{*} (SD), y | 26.5 (6.0) | 24.8 (5.4) |

Nulliparous, *n* (%) | 145 (38%) | 134 (36%) |

Family history of breast cancer, *n* (%) | 95 (25%) | 77 (20%) |

Ever use of oral contraceptives, *n* (%)^{†} | 193 (57%) | 206 (62%) |

Ever smoke cigarettes, *n* (%)^{‡} | 197 (55%) | 176 (50%) |

Mean height (SD), cm | 163.2 (6.8) | 162.6 (6.8) |

Mean weight (SD), kg | 64.2 (11.8) | 63.6 (12.9) |

Mean BMI (SD), kg/m^{2} | 24.1 (4.3) | 24.0 (4.5) |

Mean 2-OHE1 (SD), pg/mL | 271.1 (161.8) | 262.5 (154.1) |

Mean 16α-OHE1 (SD), pg/mL | 371.0 (117.1) | 363.2 (108.7) |

Mean 2-OHE1:16α-OHE1 ratio (SD) | 0.79 (0.65) | 0.76 (0.49) |