Cognitive phenotypes in probable mild Alzheimer’s disease

Abstract

AbstractBackgroundNew technologies have helped the biological diagnosis of Alzheimer’s disease to make it more accurate over the years. However, establishing prognosis for each case is still a significant challenge, as there are different cognitive profiles in the same diagnosis. Also, there is no well‐defined standard for a cognitive profile that predicts future functionality impairment. In this sense, a better understanding of cognitive phenotypes can help establishing prognosis of Alzheimer’s dementia. Our aim with this study was to identify the main cognitive profiles of patients with amnestic variant of probable Alzheimer’s dementia at a mild presentation (CDR 1) with the amnestic variant. We verified the performance of these cognitive profiles applying the neuropsychological assessment.MethodThe study comprised 141 participants with probable Alzheimer dementia, recruited from a Reference Center for the Elderly in Brazil. We conducted a complete neuropsychological assessment evaluating the following domains: memory, executive functions, language, simple attention/processing speed, and visuospatial abilities. Initially, the data were transformed in z‐scores, considering age and education, according to references for the cultural adaptations and validations for the Brazilian population. We use the K‐Nearest Neighbors (K = 3) to solve the missing data problem. After preparing the base for cluster analysis, we performed the ward’s hierarchical method and the Euclidean distance to measure similarity. Finally, we performed comparisons of the groups using the Kruskal‐Wallis tests.ResultData analysis suggested existence of five cognitive subgroups (Figure 1). Bye general comparison, performed by the Kruskal‐Wallis test, we found the groups were different in the neuropsychological assessment instruments (p<0.001). Cognitive phenotypes varied about impaired and/or preserved ability, as well as impairment severity (Figure 2). The cognitive phenotypes were different considering educational level (Figure 3). We observed accentuated global impairment cognitive phenotype in a lower level of formal education group, and less accentuated impairment profiles in a higher formal education.ConclusionIn conclusion, we identified five Cognitive phenotypes which had differences in severity of cognitive symptoms, and impaired abilities. These Cognitive phenotypes were based on different degrees of severity in visuospatial ability, simple attention/processing speed, and planning and had different education level.