Neuropsychological functioning in the acute and remitted States of late-life depression

Abstract

Late-life depression (LLD, major depression occurring in an adult 60 years or older) is a common condition that frequently presents with cognitive impairment. Up to half of individuals with LLD are estimated to have cognitive impairment greater than that of age- and education-matched comparators, with impairments of episodic memory, speed of information processing, executive functioning, and visuospatial ability being most common. To inform our understanding of the state- versus trait-effects of depression on neuropsychological functioning, and to overcome limitations of previous studies, we utilized baseline data from the longitudinal Pathways study to compare differences in single time point performance on a broad-based neuropsychological battery across three diagnostic groups of older adults, each comprised of unique participants (n = 438): currently depressed (n = 120), previously depressed but currently euthymic (n = 190), and never-depressed (n = 128). Consistent with our hypotheses, we found that participants with a history of depression (currently or previously depressed) performed significantly worse than never-depressed participants on most tests of global cognition, as well as on tests of episodic memory, attention and processing speed, verbal ability, and visuospatial ability; in general, differences were most pronounced within the domain of attention and processing speed. Contrary to our hypothesis, we did not observe differences in executive performance between the two depression groups, suggesting that certain aspects of executive functioning are "trait deficits" associated with LLD. These findings are in general agreement with the existing literature, and represent an enhancement in methodological rigor over previous studies given the cross-sectional approach that avoids practice effects on test performance.

Keywords: assessment; cognitive function; depression; elderly; geriatric; neuropsychological.

Figure 1. Standardized Test Scores Across Diagnostic Groups (Adjusting for Demographic Covariates)

Measures of global cognition and premorbid intellectual ability: Mattis Dementia Rating Scale (DRS), Mini-Mental State Exam (MMSE), and Wechsler Test of Adult Reading (WTAR). Measures of delayed memory: Logical Memory (LM) subtest of the Wechsler Memory Scale, free recall (CVLT) and recognition (CVLT-R) of the California Verbal Learning Test, California Verbal Learning Test recognition memory (CVLT-R) and delayed copy of the Modified Rey-Osterrieth Figure (MREY-D). Measures of executive functioning: Trail Making Test Part B (TRL-B), Executive Interview (EXIT), Stroop Color-Word Inhibition Test (Stroop), and Wisconsin Card-Sorting Test (WCST). Measures of attention/processing speed: Digit Symbol Substitution Test (DSST), Grooved Pegboard Test (GP), Trail Making Test Part A (TRL-A), and Finger Tapping Test (FT). Measures of verbal ability: Semantic Fluency Test (SF), Modified Boston Naming Test (MBNT), Spot the Word Test (STW), and Letter Fluency Test (LF). Measures of visuospatial ability: Block Design Test (BD), Clock Drawing Test (CDT), immediate copy of the Modified Rey-Osterrieth Figure (MREY-C), and Simple Drawings Test (SD).