Characteristic | Monozygotic pairs (N = 204) Mean (SD) | Dizygotic pairs (N = 123) Mean (SD) |
---|---|---|

Age at mammogram time 1, y | 49.75 (7.71) | 50.76 (8.61) |

Age at mammogram time 2, y | 57.61 (7.87) | 58.83 (8.60) |

Difference in age between times 1 and 2, y | 7.87 (1.57) | 8.06 (1.45) |

BMI at time 1, kg/m^{2} | 24.75 (4.17) | 25.12 (4.44) |

BMI at time 2, kg/m^{2} | 25.65 (4.33) | 25.95 (4.58) |

Dense area at time 1, cm^{2} | 30.77 (21.65) | 32.73 (23.70) |

Dense area at time 2, cm^{2} | 25.87 (20.01) | 28.76 (23.16) |

Percent dense area at time 1 | 29.92 (17.96) | 30.37 (18.60) |

Percent dense area at time 2 | 22.64 (15.78) | 23.41 (15.91) |