Impairment of attention and executive functions in chronic cerebrovascular disease and Alzheimer's disease

Abstract

To establish specific features of executive functions (EF) impairment and attention in vascular cognitive impairment (VCI) and Alzheimer's disease (AD). Eighty people (over the age of 50) diagnosed with cerebrovascular disease (CVD) and AD, as well as 29 healthy volunteers (control group), were examined. The following neuropsychological methods were used to study the quantitative and qualitative characteristics of cognitive impairments: Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), EXIT-25, Frontal Assessment Battery (FAB), Clock Drawing Test, «12 Words» test, verbal associations (literal and categorical) method, Trail Making Test A and B, Symbol-Digit Modalities Test (SDMT), Stroop Test, and Benton Visual Retention Test. Mandatory inclusion criteria in the study included having a completed magnetic resonance imaging (MRI) of the brain (in T1, T2, FLAIR, DWI, SWI modes) within 1 year before enrollment in one of the groups. No significant differences in age, sex, and level of education were found between the groups. Groups AD and CVD were also comparable in the severity of cognitive impairment overall. Attention and working memory deficits were observed in both CVD and AD, with slightly more pronounced deficits in the AD group. Qualitative analysis of individual components of working memory revealed that both CVD and AD groups had comparable cognitive control impairment compared to the control group, while AD was characterized by a more significant decrease in intellectual flexibility compared to CVD. Sustained attention was equally impaired among patients in the CVD and AD groups, with a significant difference from the control group (p<0.05). In terms of memory, it was found that auditory-verbal memory and semantic memory were significantly more affected in AD, while visual memory was impaired in both conditions. Attention and EF impairments are not specific to the «subcortical» type of cognitive disorders. Already in the early stages, AD is characterized by a significant impairment of attention and EF, and such a component of EF as intellectual flexibility suffers at the onset of AD to a greater extent than in VCI. Memory impairments are not specific to AD; already at the onset of VCI, visual memory impairment comparable to AD is noted. The obtained data can be used for early neuropsychological diagnosis and differential diagnosis of dementing cerebral diseases.