Abstract
The present study aimed to clarify the neuropsychological profile of the emergent diagnostic category of Mild Cognitive Impairment with Lewy bodies (MCI-LB) and determine whether domain-specific impairments such as in memory were related to deficits in domain-general cognitive processes (executive function or processing speed). Patients (n = 83) and healthy age- and sex-matched controls (n = 34) underwent clinical and imaging assessments. Probable MCI-LB (n = 44) and MCI-Alzheimer's disease (AD) (n = 39) were diagnosed following National Institute on Aging-Alzheimer's Association (NIA-AA) and dementia with Lewy bodies (DLB) consortium criteria. Neuropsychological measures included cognitive and psychomotor speed, executive function, working memory, and verbal and visuospatial recall. MCI-LB scored significantly lower than MCI-AD on processing speed [Trail Making Test B: p = .03, g = .45; Digit Symbol Substitution Test (DSST): p = .04, g = .47; DSST Error Check: p < .001, g = .68] and executive function [Trail Making Test Ratio (A/B): p = .04, g = .52] tasks. MCI-AD performed worse than MCI-LB on memory tasks, specifically visuospatial (Modified Taylor Complex Figure: p = .01, g = .46) and verbal (Rey Auditory Verbal Learning Test: p = .04, g = .42) delayed recall measures. Stepwise discriminant analysis correctly classified the subtype in 65.1% of MCI patients (72.7% specificity, 56.4% sensitivity). Processing speed accounted for more group-associated variance in visuospatial and verbal memory in both MCI subtypes than executive function, while no significant relationships between measures were observed in controls (all ps > .05). MCI-LB was characterized by executive dysfunction and slowed processing speed but did not show the visuospatial dysfunction expected, while MCI-AD displayed an amnestic profile. However, there was considerable neuropsychological profile overlap and processing speed mediated performance in both MCI subtypes.
Highlights
Mild Cognitive Impairment (MCI) may be conceptualized as an intermediate stage between dementia and healthy ageing in which activities of daily living are preserved (Arnáiz & Almkvist, 2003)
Patients were diagnosed as probable Mild Cognitive Impairment with Lewy bodies (MCI-LB) (n = 44), MCI-Alzheimer’s disease (AD) (n = 39) or possible MCILB (n = 21; as earlier, these were excluded from further analyses)
The present study aimed to characterize the neuropsychological profile of MCI-LB compared to MCI-AD and healthy older people, and to identify if impairments in MCI are related to deficits in domain-general cognitive resources, such as executive dysfunction or slowed processing speed
Summary
Mild Cognitive Impairment (MCI) may be conceptualized as an intermediate stage between dementia and healthy ageing in which activities of daily living are preserved (Arnáiz & Almkvist, 2003). While most commonly associated with Alzheimer’s disease (AD), MCI can be caused by other diseases and evidence-based recommendations for diagnosis of Downloaded from https://www.cambridge.org/core. IP address: 35.172.119.117, on 08 Nov 2021 at 13:57:31, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. When compared to matched test norms, some studies suggested that substantial numbers of MCI-LB present with verbal memory impairment (Ferman et al, 2013; Kemp et al, 2017), indicating amnesia should not be taken as a reliable discriminator of prodromal AD. There was heterogeneity within domains: subtypes generally differed on some but not all measures of a given domain within a single study (Ciafone et al, 2020)
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