Presymptomatic Dementia Research Articles

Cognitive trajectories preluding the onset of different dementia entities: a descriptive longitudinal study using the NACC database

ObjectiveTo describe the 10-year preclinical cognitive trajectories of older, non-demented individuals towards the onset of the four most prevalent types of dementia, i.e., Alzheimer’s disease(AD), Lewy body(LBD), vascular(VD) and frontotemporal dementia(FTD).MethodsOur analysis focused on data from older (≥ 60years) NACC (National Alzheimer’s Coordinating Center) participants. Four distinct presymptomatic dementia groups (AD-LBD-VD-FTD) and a comparison group of cognitively unimpaired(CU) participants were formed. Comprehensive cognitive assessments involving verbal episodic memory, semantic verbal fluency, confrontation naming, mental processing speed – attention and executive function – cognitive flexibility were conducted at baseline and on an approximately yearly basis. Descriptive analyses (adjusted general linear models) were performed to determine and compare the yearly cognitive scores of each group throughout the follow-up. Exploratory analyses were conducted to estimate the rates of cognitive decline.ResultsThere were 3343 participants who developed AD, 247 LBD, 108 FTD, 155 VD and 3398 composed the CU group. Participants with AD performed worse on episodic memory than those with VD and LBD for about 3 to 4 years prior to dementia onset (the FTD group documented an intermediate course). Presymptomatic verbal fluency and confrontation naming trajectories differentiated quite well between the FTD group and the remaining dementia entities. Participants with incident LBD and VD performed worse than those with AD on executive functions and mental processing speed-attention since about 5 years prior to the onset of dementia, and worse than those with FTD more proximally to the diagnosis of the disorder.ConclusionsHeterogeneous cognitive trajectories characterize the presymptomatic courses of the most prevalent dementia entities.

Validation of the "Perceptions Regarding pRE-Symptomatic Alzheimer's Disease Screening" (PRE-ADS) Questionnaire in the German Population: Attitudes, Motivations, and Barriers to Pre-Symptomatic Dementia Screening.

Attitudes, motivations, and barriers to pre-symptomatic screening for Alzheimer's disease (AD) in the general population are unclear, and validated measurement tools are lacking. Translation and validation of the German version of the "Perceptions regarding pRE-symptomatic Alzheimer's Disease Screening" (PRE-ADS) questionnaire. A convenience sample (N = 256) was recruited via an online platform. Validation of the PRE-ADS-D consisted of assessments of reliability, structural validity using Principal Component Analysis (PCA) and Exploratory Factor Analysis (EFA) and construct validity using known-group tests. A subscale "Acceptability of Screening", with 5 PRE-ADS-D items, was extracted to measure acceptance of screening in clinical practice. The STROBE checklist was used for reporting. EFA revealed a three-factor model for the PRE-ADS-D. Acceptable to good internal consistency was found for the 25-item scale (α= 0.78), as well as for the three factors "Concerns about Screening" (α= 0.85), "Intention to be Screened" (α= 0.87), and "Preventive Health Behaviors" (α= 0.81). Construct validity was confirmed for both the 25-item PRE-ADS-D and the "Acceptability of Screening" scale (α= 0.91). Overall, 51.2% of the participants showed a preference for screening. Non-parametric tests were conducted to further explore group differences of the sample. The PRE-ADS-D is a reliable and valid tool to measure attitudes, motives, and barriers regarding pre-symptomatic dementia screening in the German-speaking general population. Additionally, the subscale "Acceptability of Screening" demonstrated good construct validity and reliability, suggesting its promising potential as a practical tool in clinical practice.

Measuring attitudes, motivations and barriers to presymptomatic dementia testing

AbstractBackgroundThe increasing biomarkers testing and new methods of presymptomatic screening for dementia have risen questions like: Should people get tested? Would they want to know whether they will get this fatal, untreatable disease? This has picked the demand for a well‐structured counseling program for dementia screening. In this direction, it is important to meet the needs of the target group; however, not much is known about people with a family history of dementia attitudes about testing, the motivations and barriers, and the expectations relevant to future counseling programs about testing for dementiaMethodThis study was comprised of a validation study of a new psychometric tool and a cross‐sectional survey to assess the attitudes, buries and motivations to dementia testing. The content of the questionnaire was based on (1) a literature review, (2) the Perceptions Regarding Investigational Screening for Memory in Primary Care (PRISM‐PC) Questionnaire (M. Boustani et al., 2008), (3) a board of Clinical expert opinions. Two hundred eight (208) people enrolled in this cross sectional study. Participants came from Greece, ages ranged from 18‐70 (M = 35.5, SD = 5.7). and the majority of the sample was female (93.3%). Psychometric properties were assessed through construct validity (principal component analysis) and internal consistency (Cronbach’s alpha).ResultExploratory factor analyses revealed the presence of four factors. The first factor labelled as “Perceived harms of testing”, the second “Acceptance of testing”, the third “Perceived benefits of testing”) and the fourth factor “Need of knowledge”. The reliability of each factor separately was satisfactory to very satisfactory (.70‐.87). Cronbach’s alpha coefficient for all the final 25 items of the initial questionnaire was good (Cronbach’s α = 0.82), suggesting very satisfactory internal consistency.ConclusionThis is the first study that created a questionnaire for measuring the attitudes of Greek people towards dementia and genetic screening. Capturing data via this questionnaire might help clinicians, policymakers, and health services researchers in dementia understand better peoples’ perspectives related to the pros and cons of dementia screening and develop effective counseling programs and prevention strategies.

High-fiber-diet-related metabolites improve neurodegenerative symptoms in patients with obesity with diabetes mellitus by modulating the hippocampal-hypothalamic endocrine axis.

Through transcriptomic and metabolomic analyses, this study examined the role of high-fiber diet in obesity complicated by diabetes and neurodegenerative symptoms. The expression matrix of high-fiber-diet-related metabolites, blood methylation profile associated with pre-symptomatic dementia in elderly patients with type 2 diabetes mellitus (T2DM), and high-throughput single-cell sequencing data of hippocampal samples from patients with Alzheimer's disease (AD) were retrieved from the Gene Expression Omnibus (GEO) database and through a literature search. Data were analyzed using principal component analysis (PCA) after quality control and data filtering to identify different cell clusters and candidate markers. A protein-protein interaction network was mapped using the STRING database. To further investigate the interaction among high-fiber-diet-related metabolites, methylation-related DEGs related to T2DM, and single-cell marker genes related to AD, AutoDock was used for semi-flexible molecular docking. Based on GEO database data and previous studies, 24 marker genes associated with high-fiber diet, T2DM, and AD were identified. Top 10 core genes include SYNE1, ANK2, SPEG, PDZD2, KALRN, PTPRM, PTPRK, BIN1, DOCK9, and NPNT, and their functions are primarily related to autophagy. According to molecular docking analysis, acetamidobenzoic acid, the most substantially altered metabolic marker associated with a high-fiber diet, had the strongest binding affinity for SPEG. By targeting the SPEG protein in the hippocampus, acetamidobenzoic acid, a metabolite associated with high-fiber diet, may improve diabetic and neurodegenerative diseases in obese people.

The New Zealand Genetic Frontotemporal Dementia Study (FTDGeNZ): a longitudinal study of pre-symptomatic biomarkers

ABSTRACT The New Zealand Genetic Frontotemporal Dementia Study (FTDGeNZ) is an emerging longitudinal study of a large New Zealand pedigree with genetic frontotemporal dementia (FTD). Natural history studies of genetic FTD cohorts provide a unique opportunity to identify biomarkers of pre-symptomatic dementia, as carriers can be identified and studied decades before expected symptom onset. FTDGeNZ was established in 2016 with the aim of identifying the earliest pre-symptomatic biomarkers of FTD, in collaboration with international multi-centre cohorts. We enrolled 25 participants from a single family between April 2016 and August 2018. Participants were genotyped to determine whether they were pre-symptomatic carriers of the mutation (MAPT IVS 10 + 16 C > T), or non-carrier controls. Participants have undergone clinical assessments including neuropsychological and mood assessment; olfactory testing; assessment of social cognition; and blood collection for analyses of microRNA and protein fluid biomarkers annually. We have also performed structural and functional MRI of the brain and assessment of autobiographical memory biennially, and retinal imaging at baseline. Here, we describe the full study protocol and the baseline demographic and clinical characteristics of the FTDGeNZ cohort, and we highlight the latest findings in the field.

Later life depression as risk factor for developing dementia: epidemiological evidence, predictive models, preventive strategies and future trends.

Current investigations in pre-symptomatic dementia have suggested that depressive mood, a treatable condition, may play an important role in the development of the disorder. However, whether depression in adulthood constitute a risk factor, or a prodrome of dementia remains unclear. A major implication in such dispute is the analytic framework used to identify putative risk factors. Indeed, if evaluated in the years immediately prior to dementia diagnosis the association between depression and dementia may reflect depressive symptoms as a prodrome of yet-undiagnosed dementia. Unfortunately, long term prospective cohort investigations, reaching back into the preclinical phase of dementia are sparse. Here, we have surveyed high-quality evidence (systematic reviews and meta-analyses) on the association between depressive symptoms and increased odds of dementia. Meta-analytic findings are also presented and discussed regarding depression as a prodromal stage of dementia, or a consequence of underlying neurodegenerative processes. Additionally, the potential confounding effect of several variables on the risk association between depression and dementia, an aspect hardly investigated, is discussed. While early onset late-life depression - defined as starting before 60 years of age - increases the odds of developing dementia in predisposed subjects, late-onset depression appears to be a prodrome and a clear accelerating factor for cognitive deterioration. Since it is increasingly important to consider the potential of preemptive approaches to decrease the impact of dementia, evidence on potentially effective preventive strategies targeting depression as a risk factor, and next steps in further research are presented as concluding remarks.

DNA methylation patterns of LINE-1 and Alu for pre-symptomatic dementia in type 2 diabetes.

The identification of early markers of dementia is important for higher-risk populations such as those with type 2 diabetes (T2D). Retrotransposons, including long interspersed nuclear element 1 (LINE-1) and Alu, comprise ~40% of the human genome. Although dysregulation of these retrotransposons can induce aberrant gene regulation and genomic instability, their role in the development of pre-symptomatic dementia (PSD) among T2D patients is unknown. Here, we examined locus-specific changes in LINE-1 and Alu methylation in PSD and the potential to offset these changes via supplementation with folate and vitamin B12. We interrogated DNA methylation patterns corresponding to 22,352 probes for LINE-1 and Alu elements using publicly-available Illumina Infinium 450K methylation datasets from i) an 18-month prospective study in 28 T2D patients (GSE62003) and ii) an intervention study in which 44 individuals were supplemented with folic acid (400 μg/day) and vitamin B12 (500 μg/day) over two years (GSE74548). We identified 714 differentially methylated positions (DMP) mapping to retrotransposons in T2D patients who developed PSD in comparison to those who did not (PFDR < 0.05), comprised of 2.4% (228 probes) of all LINE-1 probes and 3.8% (486 probes) of all Alu probes. These loci were enriched in genes with functions related to Alzheimer's disease and cognitive decline, including GNB5, GNG7 and PKN3 (p < 0.05). In older individuals supplemented with folate/vitamin B12, 85 (11.9%) PSD retrotransposon loci showed significant changes in methylation (p < 0.05): participants with the MTHFR CC genotype predominantly showed hypermethylation at these loci, while hypomethylation was observed more frequently in those with the TT genotype. In T2D patients, LINE-1 and Alu elements are differentially methylated in PSD in a locus-specific manner and may offer clinical utility in monitoring risk of dementia. Further work is required to examine the potential for dietary supplementation in lowering the risk of PSD.

Blood DNA methylation signatures to detect dementia prior to overt clinical symptoms.

IntroductionThis study determined whether blood DNA methylation (DNAm) patterns differentiate individuals with presymptomatic dementia compared to controls.MethodsDNAm was measured in 73 individuals prior to dementia diagnosis and 87 cognitively healthy controls matched for age, sex, smoking, education, and baseline cognition. DNAm was also measured at 3 years follow‐up in 25 dementia cases, and 24 controls.ResultsCases and controls differed in DNAm (unadjusted P < .01) at the time of diagnosis (n = 28,787 probes), and pre‐diagnosis (n = 15,111 probes), with cg01404610 (General transcription factor IIA subunit 1 gene) significant after correction for multiple testing. Overall, 1150 probes overlapped between analyses (methylation differences from –10.6% to +11.0%), and effect sizes increased from pre‐diagnosis to diagnosis.DiscussionDiscernible blood DNAm signatures are in dementia cases before the appearance of overt clinical symptoms. Blood‐based methylation may serve as a potential biomarker of dementia, but further investigation is needed to determine their true clinical utility.

Biomarkers and brains: situating dementia in the laboratory and in the memory clinic

This paper provides a comparison of how genetic biomarkers are used (or not) in three contexts: clinic-based diagnostic work with people; lab-based research on mice and their marbles; and lab-based research on thrashing nematodes. For all the worldwide drive to find biomarkers that can be used in the detection of early, presymptomatic dementia, there is little research on how or when the association between biomarkers and a definitive disease are being made to “hold.” First, we show the disjuncture between the animal modeling that underpins laboratory attempts to stabilize genetic biomarkers and the paradigms that inform clinical diagnosis. Secondly, we develop this theme to show how in our third site, an epigenetics “worm” laboratory, neurodegenerative changes are explored as located in specific gene-environment interactions over time. We speculate whether such an enactment brings us closer to a notion of “situated biology,” to undercut possibilities of making genetic biomarkers of preclinical dementia hold.

Blood methylomic signatures of presymptomatic dementia in elderly subjects with type 2 diabetes mellitus

Due to an aging population, the incidence of dementia is steadily rising. The ability to identify early markers in blood, which appear before the onset of clinical symptoms is of considerable interest to allow early intervention, particularly in “high risk” groups such as those with type 2 diabetes. Here, we present a longitudinal study of genome-wide DNA methylation in whole blood from 18 elderly individuals with type 2 diabetes who developed presymptomatic dementia within an 18-month period following baseline assessment and 18 age-, sex-, and education-matched controls who maintained normal cognitive function. We identified a significant overlap in methylomic differences between groups at baseline and follow-up, with 8 CpG sites being consistently differentially methylated above our nominal significance threshold before symptoms at baseline and at 18 months follow up, after a diagnosis of presymptomatic dementia. Finally, we report a significant overlap between DNA methylation differences identified in converters, only after they develop symptoms of dementia, with differences at the same loci in blood samples from patients with clinically diagnosed Alzheimer's disease compared with unaffected control subjects.

TEMPORARY REMOVAL: Blood methylomic signatures of presymptomatic dementia in elderly subjects with type 2 diabetes mellitus

a Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, Devon, UK MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King’s College London, London, UK c The Joseph Sagol Neuroscience Center, Sheba Medical Center, Ramat Gan, Israel Department of Neurology, Sheba Medical Center, Ramat Gan, Israel Department of Psychiatry, The Icahn School of Medicine at Mount Sinai, New York, NY, USA

Detecting amyloid biomarkers: Embodied risk and Alzheimer prevention

The assumption of a rapidly spreading ‘epidemic’ of Alzheimer's disease (AD), the result of aging populations worldwide, coupled with no effective medication for this condition, has incited a move to bring about the prevention of AD before the appearance of clinical symptoms. The following discussion details the establishment of a research conglomerate designed to prevent AD by means of the systematic detection of biomarker changes in healthy middle-aged or younger people. Among the biomarkers currently being standardized are changes in amyloid-β in cerebrospinal fluid (CSF), and deposition of amyloid-β plaques in the living brain detectable by means of brain scans. Possession of one specific allele of the APOE gene is an additional biomarker. However, these molecular features are merely indicators of increased risk, and pre-symptomatic dementia cannot be definitively diagnosed on the basis of the presence of one or more of them. The composition, distribution, and function of the key molecule being tracked, amyloid-β, remains poorly understood and, highly significant, a large number of individuals with a heavy amyloid load in their brains live to old age with no behavioral signs of dementia. The concluding section considers preparations for a randomized controlled trial designed to detect and eliminate amyloid-β deposition very early in its formation.

Aspectos éticos del diagnóstico presintomático de la enfermedad de Alzheimer

Research into the human genome has undoubtedly opened up a new perspective in medicine. The ability to identify the cause of specific diseases, especially neurodegenerative diseases, will definitively change the concepts of disease and treatment, while advances such as antibiotic therapy and anesthesia will be relegated to history. However, the arrival of genome medicine poses major bioethical challenges, many of which remain to be resolved. We review the applicability, results and consequences of predictions based on genetic tests for presymptomatic Alzheimer's disease, as well as the dilemmas and contradictions that are already arising as a result of the commercialization of predictive tests for public use with little or no medical supervision. Given that there is currently no effective treatment of Alzheimeŕs disease, the greatest challenge and contradiction lies in managing the results of predictive tests. There are no indications for the performance of predictive genetic tests in late or sporadic Alzheimer's disease or for counselling of persons requesting these tests. The PICOGEN program provides a safe, effective, reliable and satisfactory option for persons requesting these tests who meet the inclusion criteria. Currently, caution should be the norm when considering the performance of predictive tests in presymptomatic dementia.

MR spectroscopy of brain white matter in the prediction of dementia

Previous 1H-MR spectroscopy (MRS) studies compared biochemical spectra of persons with dementia with those of healthy control subjects. Given the long prodromal period of Alzheimer disease (AD), the authors sought to investigate whether biochemical changes can be observed also in the preclinical period. The authors prospectively followed 509 elderly persons (ages 60 to 90), who were free of clinical dementia at baseline, for on average 5.9 years. At baseline, 1H-MRS of the brain (1.5 T) was performed in a plane above the lateral ventricles that comprised mainly white matter voxels. Standard ratios of N-acetyl aspartate (NAA), choline (Cho), and creatine (Cr) were calculated. Structural MRI was administered to assess white matter lesions and hippocampal atrophy. All persons were followed for incident dementia through repeated neuropsychological testing and linkage with medical records. During follow-up, 37 persons developed dementia, of whom 27 fulfilled criteria for AD. Overall, biochemical ratios on 1H-MRS at baseline were not associated with the risk of incident dementia. However, people with higher Cho/Cr ratios had a higher risk to develop dementia or AD within 4 years (hazard ratio for dementia per SD increase 1.55 [95% CI 1.05 to 2.28]). This association attenuated and became nonsignificant after adjustment for white matter lesions on MRI. These data suggest that there are biochemical changes on 1H-MR spectroscopy of brains of persons with presymptomatic dementia.