Table 1.

Mean and SD of characteristics of subjects by zygosity

CharacteristicMonozygotic pairs (N = 204) Mean (SD)Dizygotic pairs (N = 123) Mean (SD)
Age at mammogram time 1, y49.75 (7.71)50.76 (8.61)
Age at mammogram time 2, y57.61 (7.87)58.83 (8.60)
Difference in age between times 1 and 2, y7.87 (1.57)8.06 (1.45)
BMI at time 1, kg/m224.75 (4.17)25.12 (4.44)
BMI at time 2, kg/m225.65 (4.33)25.95 (4.58)
Dense area at time 1, cm230.77 (21.65)32.73 (23.70)
Dense area at time 2, cm225.87 (20.01)28.76 (23.16)
Percent dense area at time 129.92 (17.96)30.37 (18.60)
Percent dense area at time 222.64 (15.78)23.41 (15.91)