Table 2.

Growth Curve Analysis of Hippocampal Volume in Relation to APOE, BDNF and Age.^a

	Parameter Estimate (SE)	p
Initial Volumeb (Ii)
Intercept (mean, ηI)	5.04 (0.06)	<0.0001
APOE (βI1)	−0.25 (0.12)	0.042
BDNF (βI2)	−0.01 (0.12)	0.93
Change over Agec (S)
Intercept (mean, ηS)	−0.051 (0.01)	<0.0001
APOE (βS1)	0.006 (0.02)	0.74
BDNF (βS2)	0.002 (0.02)	0.92

^aThe model for the outcome at a given age was: Y_it = I_i + S*(age centered) + e_it, where the outcome Y for individual i at age t is a function of random initial level I_i . The residual e_it is assumed to be normally distributed.

^b

The model for initial volume was:

$${\mathrm{I}}_{\mathrm{i}}={\mathrm{\eta }}_{\mathrm{I}}+{\mathrm{\beta }}_{\mathrm{I}1}\ast (\text{APOE centered})+{\mathrm{\beta }}_{\mathrm{I}2}\ast (\text{BDNF centered})+\mathrm{\zeta }{\mathrm{I}}_{\mathrm{i}}$$

The random effect residual ζI_i is assumed to be normally distributed.

^c

The model for change over age (slope) was:

$$\mathrm{S}={\mathrm{\eta }}_{\mathrm{s}}+{\mathrm{\beta }}_{\mathrm{s}1}\ast (\text{APOE centered})+{\mathrm{\beta }}_{\mathrm{S}2}\ast (\text{BDNF centered})$$

APOE ε3/3 and BDNF val/met were coded as −.5; APOE ε4 and BDNF val/val were coded as +.5