Table 2. Model comparison.

No	Model description	Mathematical expression	AIC	ΔAIC
1	The Ratio (R): linear model		1527.26a	–
2	The Ratio (R): Emax model		1528.69	1.43
3	The Ratio (R): sigmoid model		1503.43	−23.83
4	The Ratio (R): logistic model		1493.96	−33.3
5	The Ratio (R): logistic model Hippocampal volume (V): linear model		1799.68b	–
6	The Ratio (R): logistic model Hippocampal volume (V): Emax model		1703.77	−95.91
7	The Ratio (R): logistic model Hippocampal volume (V): Sigmoid model		1707.04	−92.64
8	The Ratio (R): logistic model Hippocampal volume (V): Emax model ADAS-cog (S): linear model		3650.75c	–
9	The Ratio (R): logistic model Hippocampal volume (V): Emax model ADAS-cog (S): Emax model		3652.75	2

R₀ baseline of the ratio; V₀ baseline of hippocampal volume; S₀ baseline of ADAS-cog; R₀=Aβ₀/p-tau₀

R_max was fixed at 30, the largest value observed for the Ratio.

^a The AICs of model 2–4 were compared with that of model 1;

^b the AICs of model 6–7 were compared with that of model 5;

^c the AIC of model 9 was compared with that of model 8; −, not included in the OFV comparison.