Neuropsychological Comparison of Patients With Alzheimer's Disease and Dementia With Lewy Bodies

Abstract

Background and purpose: This study aimed to determine the neuropsychological differences between patients with early-stage Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) with a Clinical Dementia Rating (CDR) score of ≤1.

Methods: We examined 168 patients with AD (126 with CDR score=0.5, 42 with CDR score=1) and 169 patients with DLB (104 with CDR score=0.5, 65 with CDR score=1) whose diagnoses were supported by ¹⁸F-flobetaben positron-emission tomography (PET) and ¹⁸F-N-(3-fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) nortropane PET. Neuropsychological test scores were compared after controlling for age, sex, and education duration. Using a cutoff motor score on the Unified Parkinson's Disease Rating Scale of 20, patients with AD were further divided into AD with parkinsonism (AD^P+, n=86) and AD without parkinsonism (AD^P-, n=82).

Results: At CDR scores of both 0.5 and 1, the DLB group had lower scores on the attention (digit-span forward at CDR score=0.5 and backward at CDR score=1), visuospatial, and executive (color reading Stroop test at CDR score=0.5 and phonemic fluency test, Stroop tests, and digit symbol coding at CDR score=1) tests than the AD group, but higher scores on the memory tests. The AD^P- and AD^P+ subgroups had comparable scores on most neuropsychological tests, but the AD^P+ subgroup had lower scores on the color reading Stroop test.

Conclusions: Patients with DLB had worse attention, visuospatial, and executive functions but better memory function than patients with AD. Parkinsonism was not uncommon in the patients with AD and could be related to attention and executive dysfunction.

Keywords: Alzheimer disease; dementia with Lewy bodies; neuropsychological assessment.

Fig. 1. Comparisons of the proportion of cognitive impairment between the AD and DLB groups. Stacked bar graph illustrating the proportions of subjects with cognitive impairment according to each neuropsychological test. The proportion of subjects with z scores less than mean-1.0×SD for age- and education-matched norms are shown in bright green, while that of subjects with z scores less than mean-1.5×SD are in dark green. Stars denote significant differences (p<0.05) in the comparisons between the AD and DLB groups after corrections for multiple comparisons across 16 neuropsychological tests using the false discovery rate method. Bright stars represent significant difference in the proportion of subjects with z scores less than mean-1.0×SD, and dark stars represent z scores less than mean-1.5×SD. AD, Alzheimer’s disease; COWAT, Controlled Oral Word Association Test; DLB, dementia with Lewy bodies; DSC, digit symbol coding; K-BNT, Korean version of the Boston Naming Test; K-CWST, Korean version of the color-word Stroop test; K-TMT-E, Korean version of the Trail-Making Test for the Elderly; RCFT, Rey-Osterrieth Complex Figure Test; SD, standard deviation; SVLT, Seoul Verbal Learning Test.