Predicting progression of Alzheimer's disease

Table 1 Relationship between pre-progression category and subsequent rate of decline on cognitive and functional measures

	Progression measures
Independent Variables¶	ADAS-Cog (n = 552)		VSAT Time (n = 589)		VSAT Errors (n = 589)		CDR-SB (n = 596)		IADL (n = 573)		PSMS (n = 575)
	Beta	P	Beta	P	Beta	P	Beta	P	Beta	P	Beta	P
Duration of Symptoms	1.352	<.001	7.405	<.001	-0.778	<.001	0.446	<.001	0.523	<.001	0.243	.015
Baseline Severity (mild vs. moderate/severe)	-10.052	<001	-61.158	<001	-7.886	<.001	-3.088	<.001	-3.204	<.001	-2.129	<.001
Years of Follow-up	3.323	<.001	20.335	<.001	3.033	<.001	2.084	<.001	3.309	<.001	2.430	<.001
Years of Follow-up Squared	0.514	.036	--	NS	--	NS	--	NS	-0.207	.003	--	NS
Pre-progression Rate
Intermediate vs. Fast	-4.032	.006	-20.351	.033	-3.046	.007	-1.399	.003	-1.915	.012	-0.442	.424
Slow vs. Fast	-9.458	<.001	-49.417	<.001	-6.533	<.001	-2.593	<.001	-3.051	.001	-0.454	.520
Linear Interaction 1*	--	NS	--	NS	--	NS	0.247	.039	--	NS	--	NS
Linear Interaction 2*	--	NS	--	NS	--	NS	--	NS	--	NS	-1.133	<.001
Non-linear Interaction1*	-0.807	.004	--	NS	--	NS	--	NS	--	NS	--	NS
Non-linear Interaction 2*	-0.554	.039	--	NS	--	NS	--	NS	--	NS	--	NS
Model Intercept	56.601		617.164		62.203		10.364		14.96		4.243

* Interaction 1 = time by intermediate pre-progression group (fast = reference group); Interaction 2 = time by slow pre-progression group (fast = reference); Non-linear Interaction 1 = time squared by intermediate pre-progression group (fast = reference group); Non-linear interaction 2 = Time squared by slow pre-progression group (fast = reference group).
¶ Models adjusted for age at diagnosis, sex, years of education, duration of symptoms at diagnosis, baseline severity (categorical), pre-morbid IQ, and presence of hallucinations and/or delusions. If the quadratic term for follow-up time and the pre-progression group by quadratic time variable were not significant, coefficients for models with linear terms only are shown. Non-significant (NS) betas for interaction terms omitted from table.
ADAS-cog = Alzheimer's disease Assessment Scale-cognitive subscale; CDR-SB = Clinical Dementia Rating Scale Sum of Boxes; IADL = Instrumental Activities of Daily Living scale; PSMS = Physical Self-Maintenance Scale; VSAT = Verbal Series Attention Test.

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