Table 2.
Rates of change in whole brain and ventricular atrophy measures estimated using the step change and gradual acceleration change-point models
| Whole brain
|
Lateral ventricles
|
|||
|---|---|---|---|---|
| Step change | Gradual acceleration | Step change | Gradual acceleration | |
| Annualized rate of prechange atrophy (95% CI) | −0.28% (−0.42, −0.18) | −0.25% (−0.37, −0.11) | 1.79% (0.44, 3.58) | 1.59% (0.53, 2.91) |
| Postchange coefficient (95% CI)* | −0.84% (−1.22, −0.32) | −0.05 (−0.11, −0.01) | 6.29% (1.99, 9.18) | 0.45 (0.16, 1.17) |
| Change-point years before onset (95% CI) | 1.4 (0.5, 3.8) | 7.6 (2.3, 14.8) | 1.4 (−1.1, 13.5) | 6.0 (2.0, 15.5) |
| Atrophy rate (95% CI) | ||||
| 10–9 years before | −0.28% (−0.42, −0.18) | −0.25% (−0.39, −0.10) | 1.79% (0.44, 3.58) | 1.59% (0.44, 3.28) |
| 9–8 years before | −0.28% (−0.42, −0.18) | −0.25% (−0.38, −0.10) | 1.79% (0.44, 3.58) | 1.59% (0.43, 3.41) |
| 8–7 years before | −0.28% (−0.42, −0.18) | −0.26% (−0.38, −0.10) | 1.79% (0.44, 3.58) | 1.59% (0.43, 3.11) |
| 7–6 years before | −0.28% (−0.42, −0.18) | −0.35% (−0.66, −0.21) | 1.79% (0.44, 3.58) | 1.59% (0.26, 2.75) |
| 6–5 years before | −0.28% (−0.46, −0.18) | −0.44% (−0.77, −0.25) | 1.79% (0.46, 3.60) | 2.02% (0.64, 4.03) |
| 5–4 years before | −0.28% (−0.68, −0.18) | −0.53% (−0.86, −0.27) | 1.79% (0.41, 3.57) | 2.92% (1.20, 5.73) |
| 4–3 years before | −0.28% (−0.79, −0.15) | −0.62% (−0.95, −0.30) | 1.79% (0.30, 3.77) | 3.82% (1.49, 6.57) |
| 3–2 years before | −0.28% (−1.15, −0.14) | −0.72% (−1.04, −0.36) | 1.79% (0.30, 4.18) | 4.72% (2.00, 7.41) |
| 2–1 years before | −0.64% (−1.21, −0.20) | −0.81% (−1.16, −0.48) | 4.51% (1.82, 9.64) | 5.62% (3.17, 8.34) |
| 1–0 years before | −1.12% (−1.54, −0.66) | −0.90% (−1.27, −0.59) | 8.07% (3.27, 15.24) | 6.52% (4.34, 9.46) |
| 0–1 years after | −1.12% (−1.52, −0.63) | −0.99% (−1.39, −0.64) | 8.07% (3.00, 14.70) | 7.42% (4.93, 10.53) |
| 1–2 years after | −1.12% (−1.52, −0.64) | −1.09% (−1.53, −0.66) | 8.07% (3.18, 10.90) | 8.33% (5.39, 11.85) |
| 2–3 years after | −1.12% (−1.52, −0.64) | −1.18% (−1.70, −0.67) | 8.07% (3.50, 11.01) | 9.23% (5.76, 13.66) |
Abbreviation: CI, confidence.
For the “step change” model, the postchange coefficient parameter of the model, γ, represents the change to the atrophy rate for presymptomatic and early symptomatic carriers after the change-point and has units of percentage per year. In the “gradual acceleration” model, the postchange coefficient is proportional to the rate of acceleration in the atrophy rate after the change-point. Due to this coefficient representing a time-squared term in the model, the rate of acceleration after the change-point is a value of 2γ per year. This coefficient has units of percentage per year squared.