Table 2.

Estimates of the Gompertz mixed-effects model corresponding to normalized dense area

Unadjusted modelModel adjusted for BMIFully adjusted modela
1,064 women and 4,714 mammograms970 women and 4,320 mammograms859 women and 3,847 mammograms
Fixed effect, estimate (95% CI)
 Lower asymptote (l)3.85 (3.69–4.00)5.13 (4.66–5.61)5.30 (4.58–6.03)
 Upper asymptote (u)2.56 (2.43–2.69)3.11 (1.72–3.49)3.52 (2.91–4.13)
 Displacement along the age axis0.27 (0.20–0.33)0.26 (0.19–0.33)0.29 (0.22–0.37)
 Scale0.24 (0.28–0.20)0.25 (0.29–0.21)0.25 (0.29–0.21)
 BMI, kg/m2
  Lower asymptote−0.05 (−0.07 to −0.03)−0.04 (−0.06 to −0.02)
  Upper asymptote−0.02 (−0.03 to −0.01)−0.02 (−0.03 to −0.003)
 Menarche (13+ vs. ≤12)
  Lower asymptote−0.11 (−0.44 to 0.22)
  Upper asymptote0.23 (−0.07 to 0.53)
 Parity (1+ vs. nulliparous)
  Lower asymptote−0.78 (−1.26 to −0.29)
  Upper asymptote−0.82 (−1.28 to −0.36)
 Family history (yes vs. no)
  Lower asymptote0.68 (0.36–1.01)
  Upper asymptote0.05 (−0.27 to 0.37)
Random effect, estimate (95% CI)
 SD (lower asymptote)1.98 (1.86–2.11)1.90 (1.78–2.03)1.91 (1.78–2.05)
 SD (upper asymptote)1.89 (1.79–1.98)1.89 (1.79–1.99)1.90 (1.79–2.00)
 Correlation (l, u)0.76 (0.69–0.82)0.77 (0.69–0.83)0.77 (0.69–0.83)
Residuals, estimate (95% CI)
 SD (Residual)0.55 (0.53–0.56)0.55 (0.53–0.56)0.55 (0.53–0.56)
Correlation between mammograms taken within an individual woman (95% CI)b
 2 y apart0.94 (0.91–0.94)0.94 (0.91–0.94)0.94 (0.91–0.94)
 4 y apart0.93 (0.90–0.93)0.93 (0.89–0.93)0.93 (0.89–0.93)
 6 y apart0.92 (0.88–0.93)0.91 (0.88–0.92)0.92 (0.88–0.93)
 8 y apart0.92 (0.88–0.94)0.91 (0.88–0.94)0.91 (0.87–0.94)
 10 y apart0.91 (0.83–0.95)0.91 (0.83–0.95)0.91 (0.82–0.95)
  • aModel is adjusted for BMI at each mammogram, age at menarche, parity, and family history.

  • b95% CIs are obtained using nonparametric bootstrapping. Number of bootstrap replicates that converged; 1,030 for unadjusted model, 893 for model adjusted for BMI, and 776 for fully adjusted model.