Article Figures & Data
Figures
- Figure 1.
Examples of a dense breast (left) and a nondense breast (right).
- Figure 2.
Distribution of the absolute area of dense breast tissue (A) and absolute area of nondense breast tissue (B) by age at mammogram. Black dot, median; box widths, 1st and 3rd quartiles; whiskers, 1.5 times the interquartile range; lines outside the whiskers, outliers. If the notches on two boxes do not overlap, this indicates a difference in a location at a rough 5% significance level.
- Figure 3.
A. Variation in the log of dense breast tissue area (left y axis) and estimates of correlation of the log of dense breast tissue area for MZ and DZ pairs (right y axis) by age at mammogram. B. Variation in the log of nondense breast tissue area (left y axis) and estimates of correlation of the log of nondense breast tissue area for MZ and DZ pairs (right y axis) by age at mammogram.
Tables
- Table 1.
Characteristics of monozygous and dizygous female twin subjects
Monozygous (n = 571), mean (SE) Dizygous (n = 380), mean (SE) Age at interview (y) 50.72 (0.33) 53.03 (0.38) Age at mammogram (y) 50.65 (0.32) 52.55 (0.38) Time between interview and mammogram (mo) 6.29 (0.23) 6.14 (0.28) Weight (kg) 66.18 (0.50) 67.87 (0.61) Height (cm) 162.00 (0.26) 162.97 (0.32) Age at menarche (y) 13.04 (0.06) 12.93 (0.07) Age at first birth (y; parous women only) 24.88 (0.14) 25.07 (0.17) No. live births 2.31 (0.05) 2.42 (0.06) Years of oral contraceptive use 6.04 (0.22) 5.87 (0.27) Years of hormone replacement therapy 2.46 (0.17) 2.05 (0.21) Pack-years of smoking 5.58 (0.43) 6.97 (0.52) PMD 37.82 (0.79) 35.69 (0.96) Absolute dense area of mammographic tissue (cm2) 40.50 (0.96) 38.33 (1.17) Absolute nondense area of mammographic tissue (cm2) 78.60 (2.03) 84.78 (2.47) Total area of the breast (cm2) 119.14 (1.98) 123.05 (2.40) Parous (% yes) 84.6 85.9 Cessation of periods (% stopped) 59.3 55.0 - Table 2.
Estimates (SE) of residual variance (σ2), of monozygous and dizygous covariances (σmonozygous2 and σdizygous2, respectively), of monozygous and dizygous correlations (ρmonozygous and ρdizygous, respectively), and of heritability (H) under the AE model on log dense area and log dense area, separately
Estimate Age adjusted for mean Mean adjusted for age and covariates* Random effect a function of age† Log dense area σ2 0.63 (0.023) 0.60 (0.022) 0.43 + 0.015 (age 40) σmonozygous2 0.43 (0.025) 0.39 (0.024) 0.31 + 0.007 (age 40) σdizygous2 0.16 (0.030) 0.13 (0.029) 0.09 + 0.004 (age 40) ρmonozygous 0.67 (0.021) 0.66 (0.022) 0.73 − 0.005 (age 40) ρdizygous 0.25 (0.046) 0.21 (0.047) 0.21 + 0.001 (age 40) H 0.66 (0.022) 0.65 (0.024) 0.71 (0.039) −2 Log-likelihood 668.1 585.8 531.8 Log nondense area σ2 0.45 (0.017) 0.24 (0.0089) 0.28 − 0.004 (age 40) σmonozygous2 0.34 (0.018) 0.16 (0.0096) 0.19 − 0.002 (age 40) σdizygous2 0.15 (0.021) 0.05 (0.012) 0.06 − 0.001 (age 40) ρmonozygous 0.76 (0.017) 0.67 (0.022) 0.67 − 0.0002 (age 40) ρdizygous 0.34 (0.042) 0.21 (0.044) 0.23 − 0.002 (age 40) H 0.75 (0.017) 0.66 (0.023) 0.67 (0.036) −2 Log-likelihood −162.7 −1,165.3 −1,178.8 ↵* Adjusted covariates for mean log dense area were age, height, weight, age at menarche, number of live births, years of oral contraception use, years of hormone replacement therapy use, menopausal status, and population (Australian vs North American). Adjusted covariates for mean log nondense area were age, height, weight, age at menarche, number of live births, age at first birth, pack years of smoking, and population (Australian vs North American).
↵† These analyses allowed the random effects variables to vary as a linear function of age (centered on 40 y).
- Table 3.
Estimates (SE) of the cross-trait correlation between dense and nondense area in the same individual and the cross-trait cross-twin correlation between dense area in one twin and nondense area in the other twin
Bivariate model: log dense and log nondense Correlation in same individual Cross-correlation Monozygous pairs Dizygous pairs Mean adjusted for age −0.35 (0.023) −0.26 (0.026) −0.14 (0.034) Mean adjusted for age and covariates −0.31 (0.023) −0.20 (0.027) −0.08 (0.036)
Volume 15, Issue 4
