Table 3. Estimates of the Gompertz mixed-effects model corresponding to normalised percent dense area.
| Unadjusted model | Model adjusted for BMI | Fully adjusted Modela | |
|---|---|---|---|
|
|
|||
| 1064 women and 4714 mammograms | 970 women and 4320 mammograms | 859 women and 3847 mammograms | |
| Fixed effect, estimate (95% CI) | |||
| Lower asymptote (l) | 3.58 (3.41, 3.74) | 5.82 (5.36, 6.28) | 5.93 (5.23, 6.64) |
| Upper asymptote (u) | 1.90 (1.76, 2.04) | 2.92 (2.53, 3.31) | 3.31 (2.71, 3.90) |
| Displacement along the age axis | 0.34 (0.28, 0.40) | 0.33 (0.27, 0.40) | 0.36 (0.29, 0.43) |
| Scale | 0.19 (0.22, 0.17) | 0.21 (0.24, 0.19) | 0.21 (0.25, 0.18) |
| BMI, kg/m2 | |||
| lower asymptote | -0.09 (-0.10, -0.07) | -0.08 (-0.09, -0.06) | |
| upper asymptote | -0.03 (-0.05, -0.02) | -0.03 (-0.05, -0.02) | |
| Menarche (13+ vs ≤ 12) | |||
| lower asymptote | -0.03 (-0.36, 0.29) | ||
| upper asymptote | 0.33 (0.05, 0.62) | ||
| Parity(1+ vs nulliparous) | |||
| lower asymptote | -0.82 (-1.29, -0.36) | ||
| upper asymptote | -0.87 (-1.31, -0.42) | ||
| Family history(Yes vs No) | |||
| lower asymptote | 0.71 (0.40, 1.02) | ||
| upper asymptote | 0.12 (-0.19, 0.44) | ||
| Random effect, estimate (95% CI) | |||
| SD(lower asymptote) | 2.06 (1.93, 2.20) | 1.87 (1.74, 2.00) | 1.86 (1.73, 2.00) |
| SD(upper asymptote) | 1.85 (1.75, 1.95) | 1.82 (1.72, 1.92) | 1.81 (1.71, 1.92) |
| Correlation(l, u) | 0.71 (0.64, 0.77) | 0.71 (0.63, 0.78) | 0.72 (0.64, 0.79) |
| Residuals, estimate (95% CI) | |||
| SD(Residual) | 0.52 (0.50, 0.53) | 0.52 (0.50, 0.53) | 0.52 (0.50, 0.53) |
| Correlation between mammograms taken within an individual woman (95% CI)b | |||
| 2 years apart | 0.94 (0.91, 0.94) | 0.94 (0.90, 0.93) | 0.94 (0.90, 0.93) |
| 4 years apart | 0.93 (0.90, 0.93) | 0.92 (0.88, 0.92) | 0.92 (0.88, 0.92) |
| 6 years apart | 0.92 (0.88, 0.93) | 0.91 (0.86, 0.92) | 0.91 (0.87, 0.92) |
| 8 years apart | 0.92 (0.89, 0.94) | 0.91 (0.87, 0.93) | 0.91 (0.87, 0.93) |
| 10 years apart | 0.91 (0.83, 0.95) | 0.90 (0.81, 0.94) | 0.91 (0.80, 0.95) |
a
Model is adjusted for BMI at each mammogram, age at menarche, parity and family history.
b
95% CIs are obtained using nonparametric bootstrapping. Number of bootstrap replicates that converged; 1036 for unadjusted model, 928 for model adjusted for BMI and 821 for fully adjusted model.