. Author manuscript; available in PMC: 2015 Oct 13.

Published in final edited form as: J Alzheimers Dis. 2015 Jul 24;47(2):421–432. doi: 10.3233/JAD-150146

Table 3.

Cox Proportional Hazards Regression Analysis Showing Significant Predictors of Time to Progression from MCI (n = 39) to AD dementia (n = 11) Retained in the Final Models

Full Model χ²^‡	df	P	Predictors Retained	HR^†	95% CI	Predictor χ²* (df = 1)	p
20.63	2	<0.0001	Digit Symbol	1.07	(1.01, 1.13)	5.42	0.02
			AES-C	1.19	(1.09, 1.32)	13.02	0.0003

Initial predictors of transition from MCI to AD dementia included baseline total scores for the subject-reported Apathy Evaluation Scale (AES-S), informant-reported Apathy Evaluation Scale (AES-I), and clinician-reported Apathy Evaluation Scale (AES-C). Initial covariates included: sex, baseline age, baseline American National Adult Reading Test verbal intelligence quotient, baseline Digit Symbol score, and baseline Ray Auditory Verbal Learning Test total learning score.

AD (Alzheimer’s disease); CI (confidence interval); df (degrees of freedom); HR (hazard ratio); MCI (mild cognitive impairment).

^‡

Likelihood Ratio chi-square (χ²) test is a test of the model as a whole, whereas chi-square tests based on the Wald Test are used for individual predictors.

^†

The hazard ratio (HR) displayed for each retained predictor is the ratio of the probabilities of transitioning to AD dementia for a one unit increase in continuous predictor or a change in categories for a categorical predictor. Displayed HR’s are inverted from the original analysis results to best illustrate the effect of increasing apathy (as denoted by a decreasing AES score) on risk of progression from MCI to AD dementia.