Objective: Using a multimethod approach, this study assessed the relationship between patient and informant ratings of depression in Alzheimer's disease (AD) in a manner that better represents the progressive course of AD, and allows for elucidation of specific cognitive domains that may explain changes in respondent agreement.
Method: Case data (N = 16,297) were provided by the National Alzheimer's Coordinating Center (NACC). A series of contingency analyses were performed to assess the relationship between patient and informant agreement across levels of impairment in individuals with AD. Patients and informants were placed into groups (i.e., not impaired, mild impairment, moderate impairment, severe impairment) based on patients' performance on multiple indicators of global cognitive functioning, as well as measures of attention, working memory, processing speed, executive functioning, language, and episodic learning and memory.
Results: Across measures, greater impairment was significantly (p < .001) associated with decreases in patient-informant congruence and increases in rates of patients denying depression when informants endorsed observing features of the same. These inconsistencies were most pronounced in the mildest stages of impairment. For a subset of the sample, rates of patients reporting depressive symptoms when informants denied observing the same also increased alongside worsening impairment. Incremental impairment in episodic learning (χ² = 805.25) and memory (χ² = 856.94) performance were most closely associated with decreases in respondent agreement. Patient-informant relationship type did not appear to mediate the response patterns observed.
Conclusions: Mild impairment in AD patients, particularly in episodic learning and memory functioning, is significantly associated with decreases in patient-informant agreement regarding the presence of depressive symptoms. These results suggest that even at the earliest stages of AD informant reports should be used to corroborate patients' reporting. (PsycInfo Database Record (c) 2020 APA, all rights reserved).