Table 4.

Bivariate Dual Change Score Model of Memory and Functional Limitations over Chronological Age in the AHEAD Study: Parameter Estimates from a Spline Model for Young-old and Old-old Participants

	Memory		Functional Limitations
Parameter	Estimate	SE	Estimate	SE
Fixed effects
Initial mean µ0	53.68*	0.14	47.85*	0.19
Slope mean µS	−17.73*	1.38	44.46*	2.66
Proportion β Young-old	0.22*	0.02	−0.20*	0.02
Proportion β Old-old	0.22*	0.02	−0.19*	0.02
Coupling γ Young-old	−0.66*	0.03	0.12*	0.01
Coupling γ Old-old	−0.68*	0.04	0.11*	0.01
Random effects
Initial variance σ20	41.35*	1.27	48.42*	2.32
Slope variance σ2S	2.10*	0.33	15.38*	1.73
Residual variance Young-old σ2e	43.75*	0.66	34.89*	0.61
Residual variance Old-old σ2e	33.79*	0.51	56.78*	0.90
Covariance
Memory initial ↔ slope	−7.39*	0.62
Memory initial ↔ initial			−8.92*	1.27
Memory initial ↔ slope			22.72*	1.27
Memory slope ↔ initial			−3.72*	0.50
Memory slope ↔ slope			−5.46*	0.74
Functional Limitations initial ↔ slope			4.61*	1.06

Note. Memory and functional limitations were standardized to a T metric (M = 50, SD = 10) using the T1 AHEAD sample as the reference (N = 6,990). Young-old (aged 70 – 79); Old-old (aged 80 – 95). N = 6,990. Model Fit Statistics: χ² = 2,138.08, df = 1,096, CFI = .957, RMSEA = .012.

^*p < .01