Heterogeneity and Factorial Structure in Alzheimer's Disease: A Cognitive Perspective

Defining Alzheimer's Disease through Proteomic CSF Profiling

Alzheimer disease (AD) is the main cause of dementia, and its complexity is not yet completely understood. Proteomic profiles can provide useful information to explore the pathways involved and the heterogeneity among AD patients. A proteomic analysis was performed in cerebrospinal fluid (CSF) samples from mild cognitive impairment due to AD (MCI-AD) and control individuals; both groups were classified by amyloid β42/amyloid β40 levels in CSF (data available in BioStudies database (S-BSST1456)). The analysis based on PLS regression and volcano plot identified 7 proteins (FOLR2, PPP3CA, SMOC2, STMN1, TAGLN3, TMEM132B, and UCHL1) mainly related to protein phosphorylation, structure maintenance, inflammation, and protein degradation. Enrichment analysis revealed the involvement of different biological processes related to neuronal mechanisms and synapses, lipid and carbohydrate metabolism, immune system and inflammation, vascular, hormones, and response to stimuli, and cell signaling and adhesion. In addition, the proteomic profile showed some association with the levels of AD biomarkers in CSF. Regarding the subtypes, two MCI-AD subgroups were identified: one could be related to synapsis and neuronal functions and the other to innate immunity. The study of the proteomic profile in the CSF of AD patients reflects the heterogeneity of biochemical pathways involved in AD.

Over ninety years old: Does high cognitive reserve still help brain efficiency?

Nonagenarians and centenarians, also called oldest-old, are a very heterogeneous population that counts a limited number of individuals as it is a real challenge to reach this goal. Even if it is well known that cognitive reserve can be considered a factor in maintaining good cognitive functioning in ageing, only very few studies have been carried out on the role of cognitive reserve (CR) in the oldest-old people. The aim of this study is to investigate the relationship between cognitive reserve and cognitive functioning in a population living in a specific region of Italy, the Blue Zone in Sardinia. This population is characterised by extreme longevity and distinctive historical, geographic, social, linguistic and nutritional features. The cognitive Reserve Index questionnaire (CRIq) and the short cognitive Esame Neuropsicologico Breve-2 (ENB-2, Brief Neuropsychological Examination) were administered to 67 participants, all aged between 90 and 105 years old. The CRIq was a predictor of neuropsychological performance for the global score of the battery of tests, ENB-2 (ENB-tot) and also for 7 out of 16 of its sub-tests. All except one (Token) tapped executive functions (Interference memory at 10 and 30 s, TMT-B, Overlapping figures, Abstraction, Fluency). Results highlight that also in the oldest-old population CR has a positive effect on cognition, especially on executive functioning.

Heterogeneity of Alzheimer's disease identified by neuropsychological test profiling

Alzheimer's disease (AD) is a highly heterogeneous disorder. Untangling this variability could lead to personalized treatments and improve participant recruitment for clinical trials. We investigated the cognitive subgroups by using a data-driven clustering technique in an AD cohort. People with mild-moderate probable AD from Taiwan was included. Neuropsychological test results from the Cognitive Abilities Screening Instrument were clustered using nonnegative matrix factorization. We identified two clusters in 112 patients with predominant deficits in memory (62.5%) and non-memory (37.5%) cognitive domains, respectively. The memory group performed worse in short-term memory and orientation and better in attention than the non-memory group. At baseline, patients in the memory group had worse global cognitive status and dementia severity. Linear mixed effect model did not reveal difference in disease trajectory within 3 years of follow-up between the two clusters. Our results provide insights into the cognitive heterogeneity in probable AD in an Asian population.

Tele-Global Examination of Mental State (Tele-GEMS): an open tool for the remote neuropsychological screening

Tele-neuropsychology, i.e., the application of remote audio-visual technologies to neuropsychological evaluation or rehabilitation, has become increasingly popular and widespread during and after the COVID-19 pandemic. New tools with updated normative data and appropriate methodological developments are necessary. We present Tele-GEMS, a telephone-based cognitive screening developed on N = 601 Italian participants. It yields a global score tapping on orientation, memory, spatial representation, language, and pragmatic abilities. Its administration lasts about 10 min. Clinical cut-offs are provided, accounting for demographic variables (age, education, and sex) and also for a comprehensive index taking into account cognitively stimulating life experiences that can build up a cognitive reserve. Tele-GEMS shows good internal consistency and a good inter-rater agreement. The test includes the thresholds for estimating a significant change after repeated measurements. Tele-GEMS has a good construct validity as assessed with MoCA and a suitable criterion validity assessed with its in-person version (GEMS). All the materials and the instructions, including scripts and an online Application for the automatic calculation of cut-offs, are accessible on OSF at https://osf.io/t3bma/ under a Creative Commons license.

How Many Alzheimer-Perusini's Atypical Forms Do We Still Have to Discover?

Alzheimer-Perusini's (AD) disease represents the most spread dementia around the world and constitutes a serious problem for public health. It was first described by the two physicians from whom it took its name. Nowadays, we have extensively expanded our knowledge about this disease. Starting from a merely clinical and histopathologic description, we have now reached better molecular comprehension. For instance, we passed from an old conceptualization of the disease based on plaques and tangles to a more modern vision of mixed proteinopathy in a one-to-one relationship with an alteration of specific glial and neuronal phenotypes. However, no disease-modifying therapies are yet available. It is likely that the only way to find a few "magic bullets" is to deepen this aspect more and more until we are able to draw up specific molecular profiles for single AD cases. This review reports the most recent classifications of AD atypical variants in order to summarize all the clinical evidence using several discrimina (for example, post mortem neurofibrillary tangle density, cerebral atrophy, or FDG-PET studies). The better defined four atypical forms are posterior cortical atrophy (PCA), logopenic variant of primary progressive aphasia (LvPPA), behavioral/dysexecutive variant and AD with corticobasal degeneration (CBS). Moreover, we discuss the usefulness of such classifications before outlining the molecular-genetic aspects focusing on microglial activity or, more generally, immune system control of neuroinflammation and neurodegeneration.