Pages 811-827
Review
Alexandra M.R. McLaren, Michael D. Kawaja
Olfactory Dysfunction and Alzheimer’s Disease: A Review
Abstract: Alzheimer’s disease is the most common cause of dementia, and it is one of the leading causes of death globally. Identification and validation of biomarkers that herald the onset and progression of Alzheimer’s disease is of paramount importance for early reliable diagnosis and effective pharmacological therapy commencement. A substantial body of evidence has emerged demonstrating that olfactory dysfunction is a preclinical symptom of neurodegenerative diseases including Alzheimer’s disease. While a correlation between olfactory dysfunction and Alzheimer’s disease onset and progression in humans exists, the mechanism underlying this relationship remains unknown. The aim of this article is to review the current state of knowledge regarding the range of potential factors that may contribute to the development of Alzheimer’s disease-related olfactory dysfunction. This review predominantly focuses on genetic mutations associated with Alzheimer’s disease including amyloid-β protein precursor, presenilin 1 and 2, and apolipoprotein E mutations, that may (in varying ways) drive the cellular events that lead to and sustain olfactory dysfunction.
Pages 829-841
Review
Nuria Carcavilla-González, Gema Escalada San Adrián, Eduard Minobes-Molina, Sandra Pàmies-Tejedor, Victoria Roncal-Belzunce, Laura Atarés-Rodríguez, José Augusto García-Navarro
A Paradigm Shift on Deinstitutionalization and Dementia Care: A Narrative Review
Abstract: This narrative explores the impact of deinstitutionalization policies on the quality of life and care outcomes for individuals with Alzheimer´s disease and related dementias. We offer a historical perspective on these policies, their implications on dementia care, and the barriers to deinstitutionalization. The potential benefits of deinstitutionalization, such as improved quality of life and access to community-based support and services, are highlighted. Challenges and controversies surrounding safety, caregiver burden, and resource allocation are also examined. Ethical considerations related to the autonomy and decision-making capacity of people living with dementia are discussed. We present best practices and innovative models in dementia care that balance deinstitutionalization with appropriate care. We further put forth recommendations for future research and policy development in dementia care and deinstitutionalization, emphasizing the need for a balanced approach that respects the autonomy and preferences of people living with dementia while ensuring their safety and well-being.
Pages 843-856
Review
Simon Duchesne, Louis-Simon Rousseau, Florence Belzile, Laurie-Ann Welch, Beatrice Cournoyer, Marianne Arseneau, Véronick Lapierre, Sara-Maude Poulin, Olivier Potvin, Carol Hudon
A Scoping Review of Alzheimer’s Disease Hypotheses: An Array of Uni- and Multi-Factorial Theories
Abstract: Background: There is a common agreement that Alzheimer’s disease (AD) is inherently complex; otherwise, a general disagreement remains on its etiological underpinning, with numerous alternative hypotheses having been proposed. Objective: To perform a scoping review of original manuscripts describing hypotheses and theories of AD published in the past decades. Methods: We reviewed 131 original manuscripts that fulfilled our inclusion criteria out of more than 13,807 references extracted from open databases. Each entry was characterized as having a single or multifactorial focus and assigned to one of 15 theoretical groupings. Impact was tracked using open citation tools. Results: Three stages can be discerned in terms of hypotheses generation, with three quarter of studies proposing a hypothesis characterized as being single-focus. The most important theoretical groupings were the Amyloid group, followed by Metabolism and Mitochondrial dysfunction, then Infections and Cerebrovascular. Lately, evidence towards Genetics and especially Gut/Brain interactions came to the fore. Conclusions: When viewed together, these multi-faceted reports reinforce the notion that AD affects multiple sub-cellular, cellular, anatomical, and physiological systems at the same time but at varying degree between individuals. The challenge of providing a comprehensive view of all systems and their interactions remains, alongside ways to manage this inherent complexity.
Pages 857-867
Review
Bilal Irfan, Ghadeer Ankouni, Jonathan Reader, Navid Seraji-Bozorgzad, Bruno Giordani, Kelly Bakulski, Arijit Bhaumik, Benjamin M. Hampstead, Annalise Rahman-Filipiak
Alzheimer’s Disease and Related Dementias in Muslim Women: Recommendations for Culturally Sensitive Care
Abstract: Alzheimer's disease and related dementias (ADRD) present significant challenges including cognitive and functional loss, behavioral disruption, emotional distress, and significant financial burden. These stressors are amplified in minority groups, who experience higher rates of ADRD but less frequent and later diagnosis. There is therefore a critical need to identify tangible approaches to culturally informed dementia assessment and care for patients from diverse communities. Muslim patients and particularly Muslim women are among the populations most understudied in the ADRD space. Muslim patients may hold unique religious, spiritual, and cultural beliefs and practices that can impact care-seeking for dementia symptoms, diagnostic accuracy, and treatment uptake. This paper outlines culturally informed approaches to assessing and treating Muslim women and families at each stage of ADRD care, though many recommendations extend to the broader Muslim community and others of diverse racial-ethnic backgrounds. We provide concrete suggestions for building rapport within and leveraging common family structures, respecting principles of modesty and privacy for all women including those who observe hijab or niqab, and communicating dementia diagnosis and care in the context of spiritual and ethical beliefs. While not intended as a comprehensive and prescriptive guide, this review provides important points of consideration and discussion with patients of Muslim backgrounds.
Pages 869-876
Short Communication
Catherine Diaz-Asper, Chelsea Chandler, Brita Elvevåg (Handling Associate Editor: Kelsey Thomas)
Cognitive Screening for Mild Cognitive Impairment: Clinician Perspectives on Current Practices and Future Directions
Abstract: This study surveyed 51 specialist clinicians for their views on existing cognitive screening tests for mild cognitive impairment and their opinions about a hypothetical remote screener driven by artificial intelligence (AI). Responses revealed significant concerns regarding the sensitivity, specificity, and time taken to administer current tests, along with a general willingness to consider adopting telephone-based screening driven by AI. Findings highlight the need to design screeners that address the challenges of recognizing the earliest stages of cognitive decline and that prioritize not only accuracy but also stakeholder input.
Pages 877-881
Commentary
Alberto J. Espay, Karl Herrup, Bruno P. Imbimbo, Kasper P. Kepp, Timothy Daly
Recalibrating the Risk-Benefit Profiles of Lecanemab and Donanemab: Scales, Immunoreactivity, and Changes in Amyloid-β42
Abstract: Three recent anti-amyloid-β antibody trials for Alzheimer’s disease reported similar effect sizes, used non-reactive saline as placebo, and showed large numbers of adverse events including imaging anomalies (ARIA) that correlate with cognitive changes. Conversely, all previous antibody trials were less reactive and pronounced ineffective. We argue that these observations point to unblinding bias, inflating apparent efficacy and thus altering the risk-benefit balance. Further, we highlight data demonstrating that beyond reducing amyloid, monoclonal antibodies increase monomeric amyloid-β42 in cerebrospinal fluid, which may explain potential benefits. We should recalibrate the efficacy of these antibodies and devote more resources into strategies beyond removing amyloid.
Pages 883-885
Commentary
Laura Beth McIntire
Prognostic Power? Do the Plasma Biomarkers, Neurofilament Light and Phospho-Tau 181, Improve Prediction of Progression to Alzheimer’s Disease Using a Machine Learning Approach in the ADNI Cohort?
Abstract: With the advent of therapeutics with potential to slow Alzheimer’s disease progression the necessity of understanding the diagnostic value of plasma biomarkers is critical, not only for understanding the etiology and progression of Alzheimer’s disease, but also for access and response to potentially disease modifying therapeutic agents. Multiple studies are currently assessing the sensitivity and specificity of plasma biomarkers in large cohorts such as the Alzheimer's Disease Neuroimaging Initiative. This study uses machine learning to predict the progression from mild cognitive impairment using plasma biomarkers in conjunction with well-established cerebrospinal fluid and imaging biomarkers of disease progression.
Pages 887-897
José A. Reyes Bueno, Guillermo Sánchez-Guijo, Pablo Doblas Ráez, Juan A. García-Arnés, Francisco J. Garzón-Maldonado, Vicente Serrano Castro, Carlos de la Cruz-Cosme, Carmen Alba-Linero, Mario Gutiérrez-Bedmar, Natalia García-Casares
Effects of Type 2 Diabetes on the Neuropsychological Profile in Mild Cognitive Impairment
Abstract: Background: Diabetes is one of the main risk factors for developing mild cognitive impairment (MCI) and Alzheimer’s disease. Most studies have demonstrated a worse performance in executive function, verbal fluency, and information processing speed in patients with diabetes. Objective: To assess the cognitive functioning of persons with type 2 diabetes and amnesic mild cognitive impairment (aMCI-T2DM) compared to persons with aMCI without diabetes and persons without diabetes or aMCI as controls, to understand the role of diabetes in the neuropsychological profile. Methods: Cross-sectional study involving a sample of 83 patients, ranging in age from 61 to 85 years and divided into three groups: aMCI-T2DM (27 patients), aMCI (29 patients), Controls (27 individuals). All the participants undertook an exhaustive neuropsychological assessment (auditory-verbal and visual memory, attention, information processing speed, language, executive function, and depression). Results: Both groups of aMCI patients performed significantly worse than the controls in all the neuropsychological tests. A significant linear tendency (p trend <0.05) was found between groups, with the aMCI-T2DM group presenting worse results in global cognition assessed by the Mini-Mental State Examination and Montreal Cognitive Assessment; Rey-Osterrieth Complex Figure Test; Auditory Verbal Learning Test; Trail Making Test A and B, Verbal Fluency Test, and Hamilton Depression Rating Scale. Conclusions: aMCI patients with or without diabetes showed worse cognitive function compared to persons without diabetes or aMCI. Additionally, aMCI patients without T2DM presented a different cognitive profile than aMCI patients with T2DM, which tended towards presenting worse cognitive functions such as global cognition, memory, attention, executive function, and language.
Pages 899-910
Cosimo Tuena, Silvia Serino, Karine Marie Goulene, Elisa Pedroli, Marco Stramba-Badiale, Giuseppe Riva
Bodily and Visual-Cognitive Navigation Aids to Enhance Spatial Memory Recall in Mild Cognitive Impairment
Abstract: Background: Individuals with mild cognitive impairment (MCI) syndrome often report navigation difficulties, accompanied by impairments in egocentric and allocentric spatial memory. However, studies have shown that both bodily (e.g., motor commands, proprioception, vestibular information) and visual-cognitive (e.g., maps, directional arrows, attentional markers) cues can support spatial memory in MCI. Objective: We aimed to assess navigation cues for innovative spatial training in aging. Methods: Fifteen MCI patients were recruited for this study. Their egocentric and allocentric memory recall performances were tested through a navigation task with five different virtual reality (VR) assistive encoding navigation procedures (bodily, vision only, interactive allocentric map, reduced executive load, free navigation without cues). Bodily condition consisted of an immersive VR setup to engage self-motion cues, vision only condition consisted of passive navigation without interaction, in the interactive allocentric map condition patients could use a bird-view map, in the reduced executive load condition directional cues and attentional markers were employed, and during free navigation no aid was implemented. Results: Bodily condition improved spatial memory compared to vision only and free navigation without cues. In addition, the interactive allocentric map was superior to the free navigation without cues. Surprisingly, the reduced executive load was comparable to vison only condition. Moreover, a detrimental impact of free navigation was observed on allocentric memory across testing trials. Conclusions: These findings challenge the notion of an amodal representation of space in aging, suggesting that spatial maps can be influenced by the modality in which the environment was originally encoded.
Pages 911-925
Mengxin Zhu, Yang Liu, Chen Chen, Hao Chen, Wanyan Ni, Yuanjian Song, Bingchen Lv, Fang Hua, Guiyun Cui, Zuohui Zhang
TLR4/Rac1/NLRP3 Pathway Mediates Amyloid-β-Induced Neuroinflammation in Alzheimer’s Disease
Abstract: Background: Neuroinflammation plays a crucial part in the initial onset and progression of Alzheimer's disease (AD). NLRP3 inflammasome was demonstrated to get involved in amyloid-β (Aβ)-induced neuroinflammation. However, the mechanism of Aβ-triggered activation of NLRP3 inflammasome remains poorly understood. Objective: Based on our previous data, the study aimed to identify the downstream signals that bridge the activation of TLR4 and NLRP3 inflammasome associated with Aβ. Methods: BV-2 cells were transfected with TLR4siRNA or pretreated with a CLI-095 or NSC23766, followed by Aβ1-42 treatment. APP/PS1 mice were injected intraperitoneally with CLI-095 or NSC23766. NLRP3 inflammasome and microglia activation was detected with immunostaining and western blot. G-LISA and Rac1 pull-down activation test were performed to investigate the activation of Rac1. Real-time PCR and ELISA were used to detect the inflammatory cytokines. Aβ plaques were assessed by western blotting and immunofluorescence staining. Morris water maze test was conducted to determine the spatial memory in mice. Results: Rac1 and NLRP3 inflammasome were activated by Aβ in both in vitro and in vivo experiments. Inhibition of TLR4 reduced the activity of Rac1 and NLRP3 inflammasome induced by Aβ1-42. Furthermore, inhibition of Rac1 blocked NLRP3 inflammasome activation mediated by TLR4. Blocking the pathway by CLI095 or NSC23766 suppressed Aβ1–42-triggered activation of microglia, reduced the expression of pro-inflammatory mediators and ameliorated the cognition deficits in APP/PS1 mice. Conclusions: Our study demonstrated that TLR4/Rac1/NLRP3 pathway mediated Aβ-induced neuroinflammation, which unveiled a novel pathway and key contributors underlying the pathogenic mechanism of Aβ.
Pages 927-939
Rekha Khandia, Pankaj Gurjar, Victoria Romashchenko, Sami A. Al-Hussain, Athanasios Alexiou, George Zouganelis, Magdi E.A. Zaki (Handling Associate Editor: Anas Shamsi)
In-silico Codon Context and Synonymous Usage Analysis of Genes for Molecular Mechanisms Inducing Autophagy and Apoptosis with Reference to Neurodegenerative Disorders
Abstract: Background: Autophagy and apoptosis are cellular processes that maintain cellular homeostasis and remove damaged or aged organelles or aggregated and misfolded proteins. Stress factors initiate the signaling pathways common to autophagy and apoptosis. An imbalance in the autophagy and apoptosis, led by cascade of molecular mechanism prior to both processes culminate into neurodegeneration. Objective: In present study, we urge to investigate the codon usage pattern of genes which are common before initiating autophagy and apoptosis Methods: In the present study, we took up eleven genes (DAPK1, BECN1, PIK3C3 (VPS34), BCL2, MAPK8, BNIP3L (NIX), PMAIP1, BAD, BID, BBC3, MCL1) that are part of molecular signaling mechanism prior to autophagy and apoptosis. We analyzed dinucleotide odds ratio, codon bias, usage, context, and rare codon analysis. Results: CpC and GpGdinucleotides were abundant, with the dominance of G/C ending codons as preferred codons. Clustering analysis revealed that MAPK8 had a distinct codon usage pattern compared to other envisaged genes. Both positive and negative contexts were observed, and GAG-GAG followed by CTG-GCC was the most abundant codon pair. Of the six synonymous arginine codons, two codons CGT and CGA were the rarest. Conclusions: The information presented in the study may be used to manipulate the process of autophagy and apoptosis and to check the pathophysiology associated with their dysregulation.
Pages 941-952
Jeroen Bruinsma, Vasileios S. Loukas, Thomas Kassiotis, Irene Heger, Anna Rosenberg, Leonie N. C. Visser, Francesca Mangialasche, Dimitrios I. Fotiadis, Sten Hanke, Rik Crutzen
Socio-Cognitive Determinants of Lifestyle Behavior in the Context of Dementia Risk Reduction: A Population-Based Study in the Netherlands
Abstract: Background: Unhealthy behavior increases the risk of dementia. Various socio-cognitive determinants influence whether individuals persist in or alter these unhealthy behaviors. Objective: This study identifies relevant determinants of behavior associated to dementia risk. Methods: 4,104 Dutch individuals (40-79 years) completed a screening questionnaire exploring lifestyle behaviors associated with dementia risk. Subsequently, 3,065 respondents who engaged in one or more unhealthy behaviors completed a follow-up questionnaire investigating socio-cognitive determinants of these behaviors. Cross-tables were used to assess the accuracy of participants' perceptions regarding their behavior compared to recommendations. Confidence Interval-Based Estimation of Relevance (CIBER) was used to identify the most relevant determinants of behavior based on visual inspection and interpretation. Results: Among the respondents, 91.3% reported at least one, while 65% reported two or more unhealthy lifestyle behaviors associated to dementia risk. Many of them were not aware they did not adhere to lifestyle recommendations. The most relevant determinants identified include attitudes (i.e., lacking a passion for cooking and finding pleasure in drinking alcohol or smoking), misperceptions on social comparisons (i.e., overestimating healthy diet intake and underestimating alcohol intake), and low perceived behavioral control (i.e., regarding changing physical inactivity, altering diet patterns, and smoking cessation). Conclusions: Individual-level interventions that encourage lifestyle change should focus on enhancing accurate perceptions of behaviors compared to recommendations, while strengthening perceived control towards behavior change. Given the high prevalence of dementia risk factors, combining interventions at both individual and environmental levels are likely to be the most effective strategy to reduce dementia on a population scale.
Pages 953-963
Kenichiro Sato, Yoshiki Niimi, Ryoko Ihara, Kazushi Suzuki, Atsushi Iwata, Takeshi Iwatsubo, Alzheimer’s Disease Neuroimaging Initiative, Japanese Alzheimer’s Disease Neuroimaging Initiative
Simplifying Alzheimer's Disease Monitoring: A Novel Machine-Learning Approach to Estimate the Clinical Dementia Rating Sum of Box Changes Using the Mini-Mental State Examination and Functional Activities Questionnaire
Abstract: Background: Primary outcome measure in the clinical trials of disease modifying therapy (DMT) drugs for Alzheimer’s disease (AD) has often been evaluated by Clinical Dementia Rating sum of boxes (CDRSB). However, CDR testing requires specialized training and 30-50 minutes to complete, not being suitable for daily clinical practice. Objective: Herein, we proposed a machine-learning method to estimate CDRSB changes using simpler cognitive/functional batteries (Mini-Mental State Examination [MMSE] and Functional Activities Questionnaire [FAQ]), to replace CDR testing. Methods: Baseline data from 944 ADNI and 171 J-ADNI amyloid-positive participants were used to build machine-learning models predicting annualized CDRSB changes between visits, based on MMSE and FAQ scores. Prediction performance was evaluated with mean absolute error (MAE) and R2 comparing predicted to actual ΔCDRSB/Δyear. We further assessed whether decline in cognitive function surpassing particular thresholds could be identified using the predicted ΔCDRSB/Δyear. Results: The models achieved the minimum required prediction errors (MAE < 1.0) and satisfactory prediction accuracy (R2 > 0.5) for mild cognitive impairment (MCI) patients for changes in CDRSB over periods of 18 months or longer. Predictions of annualized CDRSB progression > 0.5, >1.0, or >1.5 demonstrated a consistent performance (i.e., Matthews correlation coefficient > 0.5). These results were largely replicated in the J-ADNI case predictions. Conclusions: Our method effectively predicted MCI patient deterioration in the CDRSB based solely on MMSE and FAQ scores. It may aid routine practice for disease-modifying therapy drug efficacy evaluation, without necessitating CDR testing at every visit.
Pages 965-980
Joanna Su Xian Chong*, Yi Jayne Tan*, Amelia Jialing Koh, Simon Kang Seng Ting, Nagaendran Kandiah, Adeline Su Lyn Ng, Juan Helen Zhou (Handling Associate Editor: Michela Pievani) *These authors contributed equally to this work.
Plasma Neurofilament Light Relates to Divergent Default and Salience Network Connectivity in Alzheimer’s Disease and Behavioral Variant Frontotemporal Dementia
Abstract: Background: Alzheimer’s disease (AD) and behavioral variant frontotemporal dementia (bvFTD) show differential vulnerability to large-scale brain functional networks. Plasma neurofilament light (NfL), a promising biomarker of neurodegeneration, has been linked in AD patients to glucose metabolism changes in AD-related regions. However, it is unknown whether plasma NfL would be similarly associated with disease-specific functional connectivity changes in AD and bvFTD. Objective: Our study examined the associations between plasma NfL and functional connectivity of the default mode and salience networks in patients with AD and bvFTD. Methods: Plasma NfL and neuroimaging data from patients with bvFTD (n = 16) and AD or mild cognitive impairment (n = 38; AD+MCI) were analyzed. Seed-based functional connectivity maps of key regions within the default mode and salience networks were obtained and associated with plasma NfL in these patients. Results: We demonstrated divergent associations between NfL and functional connectivity in AD+MCI and bvFTD patients. Specifically, AD+MCI patients showed lower default mode network functional connectivity with higher plasma NfL, while bvFTD patients showed lower salience network functional connectivity with higher plasma NfL. Further, lower NfL-related default mode network connectivity in AD+MCI patients was associated with lower Montreal Cognitive Assessment scores and higher Clinical Dementia Rating sum-of-boxes scores, although NfL-related salience network connectivity in bvFTD patients was not associated with Neuropsychiatric Inventory Questionnaire scores. Conclusions: Our findings indicate that plasma NfL is differentially associated with brain functional connectivity changes in AD and bvFTD.
Pages 981-991
Jocelyn Jaen, Francine Grodstein, Martín Lajous, Omar Yaxmehen Bello-Chavolla, Liliana Gómez-Flores-Ramos, Jingyun Yang, David A. Bennett, David X. Marquez, Melissa Lamar (Handling Associate Editor: Megan Zuelsdorff)
Associations of Nativity and the Role of the Hispanic Paradox on the Cognitive Health of Older Latinos Living in the United States
Abstract: Background: US-based Latinos have lower education and income combined with higher health risks than non-Latino whites, but often ‘paradoxically’ evidence better health-related outcomes. Less work has investigated this paradox for cognitive-related outcomes despite nativity diversity. Objective: We evaluated cognitive aging within older Latinos of diverse nativity currently living in the US and participating in Rush Alzheimer’s Disease Center studies. Methods: Participants without baseline dementia, who completed annual neuropsychological assessments (in English or Spanish) were grouped by US-born (n=117), Mexico-born (n=173), and born in other Latin American regions (LAr-born=128). Separate regression models examined associations between nativity and levels of (N=418) or change in (n=371; maximum follow-up ~16 years) global and domain-specific cognition. Results: Demographically-adjusted linear regression models indicated that foreign-born nativity was associated with lower levels of global cognition and select cognitive domains compared to US-born Latinos. No associations of nativity with cognitive decline emerged from demographically-adjusted mixed-effects models; however, Mexico-born nativity appeared associated with slower declines in working memory compared to other nativity groups (p-values>0.051). Mexico-born Latinos had relatively higher vascular burden and lower education levels than other nativity groups; however, this did not alter results. Conclusions: Nativity differences in baseline cognition may be due, in part, to accumulated stressors related to immigration and acculturation experienced by foreign-born Latinos which may hasten meeting criteria for dementia later in life. In contrast, Mexico-born participants’ slower working memory declines, taken in the context of other participant characteristics including vascular burden, suggests the Hispanic Paradox may relate to factors with the potential to affect cognition.
Pages 993-1004
Linlin Wang, Xuezhen Zhang, Lei Wang, Miaomiao Guo, Qihang Yang, Xiaogang Chen, Hong Sha (Handling Associate Editor: Tahera Ahmed)
Association of Age with Dual-Task Objective Cognitive Indicators and Gait Parameters in Older Adults
Abstract: Background: Early recognition of dementia like Alzheimer’s disease is crucial for disease diagnosis and treatment, and existing objective tools for early screening of cognitive impairment are limited. Objective: To investigate age-related behavioral indicators of dual-task cognitive performance and gait parameters and to explore potential objective markers of early cognitive decline. Methods: The community-based cognitive screening data was analyzed. Hierarchical cluster analysis and Pearson correlation analysis were performed on the 9-item subjective cognitive decline (SCD-9) scores, walking-cognitive dual-task performance, walking speed, and gait parameters of 152 participants. The significant differences of indicators that may related to cognitive decline were statistically analyzed across six age groups. A mathematical model with age as the independent variable and motor cognition composite score as the dependent variable was established to observe the trend of motor cognition dual-task performance with age. Results: Strong correlation was found between motor cognitive scores and SCD and age. Gait parameters like the mean value of ankle angle, the left-right difference rate of ankle angle and knee angle and the coefficient of variation of gait cycle showed an excellent correlation with age. Motor cognition scores showed a decreasing trend with age. The slope of motor cognition scores with age after 50 years (k = -1.06) was six times higher than that before 50 years (k = -0.18). Conclusions: Cognitive performance and gait parameters in the walking-cognitive dual-task state are promising objective markers that could characterize age-related cognitive decline.
Pages 1005-1022
Can Wu, Tingting Ruan, Yalan Yuan, Chunshuang Xu, Lijuan Du, Fang Wang, Shujun Xu (Handling Associate Editor: Ling-Qiang Zhu)
Alterations in Synaptic Connectivity and Synaptic Transmission in Alzheimer’s Disease with High Physical Activity
Abstract: Background: Alzheimer's disease (AD) is a progressive neurodegeneration disease. Physical activity is one of the most promising modifiable lifestyles that can be effective in slowing down the progression of AD at an early stage. Objective: Explore the molecular processes impaired in AD that were conversely preserved and enhanced by physical activity. Methods: Integrated transcriptomic analyses were performed in datasets that contain AD patients and elders with different degrees of physical activity. The changes of the hub genes were validated through analyzing another two datasets. The expression of the hub genes was further detected in the hippocampus and cortexes of APP/PS1 transgenic mice with or without physical activity by Quantitative polymerase chain reaction (qPCR). Results: Cross-comparison highlighted 195 DEGs displaying opposed regulation patterns between AD and high physical activity (HPA). The common DEGs were predominantly involved in synaptic vesicle recycling and synaptic transmission, largely downregulated in AD patients but upregulated in the elders with HPA. Two key modules and four hub genes that were related to synaptic vesicle turnover were obtained from the PPI network. The expression of these hub genes (SYT1, SYT4, SH3GL2, and AP2M1) was significantly decreased in AD transgenic mice and was reversed by HPA training. Conclusions: HPA may reverse AD pathology by upregulating a range of synaptic vesicle transport related proteins which might improve the efficiency of synaptic vesicle turnover and facilitate inter-neuronal information transfer. The study provides novel insights into the mechanisms underlining the protective effects of HPA on AD.
Pages 1023-1032
Hossam Youssef, Rodolfo G. Gatto, Nha Trang Thu Pham, Ronald C. Peterson, Mary M. Machulda, R. Ross Reichard, Dennis W. Dickson, Clifford R. Jack, Jennifer L. Whitwell, Keith A. Josephs
TDP-43 Is Associated with Subiculum and Cornu Ammonis 1 Hippocampal Subfield Atrophy in Primary Age-Related Tauopathy
Abstract: Background: TAR DNA binding protein 43 (TDP-43) has been shown to be associated with whole hippocampal atrophy in primary age-related tauopathy (PART). It is currently unknown which subregions of the hippocampus are contributing to whole hippocampal atrophy in PART. Objective: To identify which specific hippocampal subfield regions are contributing to TDP-43-associated whole hippocampal atrophy in PART. Methods: A total of 115 autopsied cases from the Mayo Clinic Alzheimer Disease Research Center and the Mayo Clinic Study of Aging were analyzed. All cases underwent antemortem brain volumetric MRI, neuropathological assessment of the distribution of Aβ (Thal phase), and neurofibrillary tangle (Braak stage) to diagnose PART, as well as assessment of TDP-43 presence/absence in the amygdala, hippocampus and beyond. Hippocampal subfield segmentation was performed using FreeSurfer version 7.4.1. Statistical analyses using logistic regression were performed to assess for associations between TDP-43 and hippocampal subfield volumes, accounting for potential confounders. Results: TDP-43 positive patients (n=37, 32%), of which 15/15 were type-α, had significantly smaller whole hippocampal volumes, and smaller volumes of the body and tail of the hippocampus compared to TDP-43 negative patients. Subfield analyses revealed an association between TDP-43 and the molecular layer of hippocampal body and the body of cornu ammonis 1 (CA1), subiculum, and presubiculum regions. There was no association between TDP-43 stage and subfield volumes. Conclusions: Whole hippocampal volume loss linked to TDP-43 in PART is mainly due to volume loss occurring in the molecular layer, CA1, subiculum and presubiculum of the hippocampal body.
Pages 1033-1046
Olov Rolandsson, Andreas Tornevi, Pär Steneberg, Helena Edlund, Tommy Olsson, Ulf Andreasson, Henrik Zetterberg, Kaj Blennow
Acute Hyperglycemia Induced by Hyperglycemic Clamp Affects Plasma Amyloid-β in Type 2 Diabetes
Abstract: Background: Individuals with type 2 diabetes (T2D) have an increased risk of cognitive symptoms and Alzheimer’s disease (AD). Mis-metabolism with aggregation of amyloid-β peptides (Aβ) play a key role in AD pathophysiology. Therefore, human studies on Aβ metabolism and T2D are warranted. Objective: The objective of this study was to examine whether acute hyperglycemia affects plasma Aβ1-40 and Aβ1-42 concentrations in individuals with T2D and matched controls. Methods: Ten participants with T2D and 11 controls (median age, 69 years; range, 66–72 years) underwent hyperglycemic clamp and placebo clamp (saline infusion) in a randomized order, each lasting 4 hours. Aβ1-40, Aβ1-42, and insulin-degrading enzyme (IDE, an important Aβ-degrading) plasma concentrations were measured in blood samples taken at 0 and 4 hours of each clamp. Linear mixed-effect regression models were used to evaluate the 4-hour changes in Aβ1-40 and Aβ1-42 concentrations, adjusting for body mass index, estimated glomerular filtration rate, and 4-hour change in insulin concentration. Results: At baseline, Aβ1-40 and Aβ1-42 concentrations did not differ between the two groups. During the hyperglycemic clamp, Aβ decreased in the control group, compared to the placebo clamp (Aβ1-40: p = 0.034, Aβ1-42: p = 0.020), IDE increased (p = 0.016) during the hyperglycemic clamp, whereas no significant changes in either Aβ or IDE was noted in the T2D group. Conclusions: Clamp-induced hyperglycemia was associated with increased IDE levels and enhanced Aβ40 and Aβ42 clearance in controls, but not in individuals with T2D. We hypothesize that insulin-degrading enzyme was inhibited during hyperglycemic conditions in people with T2D.
Pages 1047-1064
Mayra L. Estrella, Wassim Tarraf, Sayaka Kuwayama, Linda C. Gallo, Christian R. Salazar, Ariana M. Stickel, Josiemer Mattei, Priscilla M. Vásquez, Kamal M. Eldeirawi, Krista M. Perreira, Frank J. Penedo, Carmen R. Isasi, Jianwen Cai, Donglin Zeng, Hector M. González, Martha L. Daviglus, Melissa Lamar
Associations of Allostatic Load with Level of and Change in Cognitive Function Among Middle-Aged and Older Hispanic/Latino Adults: The Study of Latinos-Investigation of Neurocognitive Aging (SOL-INCA)
Abstract: Background: Higher allostatic load (AL), a multi-system measure of physiological dysregulation considered a proxy for chronic stress exposure, is associated with poorer global cognition (GC) in older non-Hispanic white adults. However, evidence of these associations in middle-aged and older US-based Hispanic/Latino adults is limited. Objective: To examine associations of AL with level of cognition, performance in cognition 7 years later, and change in cognition over 7 years among middle-aged and older US-based Hispanic/Latino adults. Methods: We used data (n=5,799, 45-74 years at baseline) from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) and SOL-Investigation of Neurocognitive Aging (SOL-INCA). The AL score comprised 16 biomarkers representing cardiometabolic, glucose, cardiopulmonary, parasympathetic, and inflammatory systems (higher scores=greater dysregulation). Cognitive outcomes included GC and individual tests of verbal learning and memory, world fluency (WF), Digit Symbol Substitution (DSS), and Trail Making (Parts A & B). Survey-linear regressions assessed associations of AL with performance in cognition at baseline, 7 years later, and via 7-year cognitive change scores adjusting for sociodemographic characteristics, lifestyle factors, and depressive symptoms. Results: Higher AL was associated with lower baseline performance in GC and WF; and lower 7-year follow-up performance in these same measures plus DSS and Trail Making Parts A & B. Higher AL was associated with more pronounced 7-year change (reduction) in GC and on WF and DSS tests. Conclusions: Findings extend previous evidence in predominantly older non-Hispanic white cohorts to show that AL is related to level of and change in GC (as well as WF and DSS) among middle-aged and older US-based Hispanic/Latino adults.
Pages 1065-1075
Byron J. Aguilar, Guneet K. Jasuja, Xuyang Li, Ekaterina Shishova, Natalia Palacios, Dan Berlowitz, Peter Morin, Maureen K O’Connor, Andrew Nguyen, Joel Reisman, Yue Leng, Raymond Zhang, Amir Abbas Tahami Monfared, Quanwu Zhang, Weiming Xia (Handling Associate Editor: Bruce Citron)
Prevalence of Mild Cognitive Impairment and Alzheimer’s Disease Identified in Veterans in the United States
Abstract: Background: Diagnostic codes can be instrumental for case identification in Alzheimer’s disease (AD) research; however, this method has known limitations and cannot distinguish between disease stages. Clinical notes may offer more detailed information including AD severity and can complement diagnostic codes for case identification. Objective: To estimate prevalence of mild cognitive impairment (MCI) and AD using diagnostics codes and clinical notes available in the electronic healthcare record (EHR). Methods: This was a retrospective study in the Veterans Affairs Healthcare System (VAHS). Health records from Veterans aged 65 years or older were reviewed during Fiscal Years (FY) 2010-2019. Overall, 274,736 and 469,569 Veterans were identified based on a rule-based algorithm as having at least one clinical note for MCI and AD, respectively; 201,211 and 149,779 Veterans had a diagnostic code for MCI and AD, respectively. During FY 2011-2018, likely MCI or AD diagnosis was defined by ≥2 qualifiers (i.e., notes and/or codes) ≥30 days apart. Veterans with only 1 qualifier were considered as suspected MCI/AD. Results: Over the 8-year study, 147,106 and 207,225 Veterans had likely MCI and AD, respectively. From 2011 to 2018, yearly MCI prevalence increased from 0.9% to 2.2%; yearly AD prevalence slightly decreased from 2.4% to 2.1%; mild AD changed from 22.9% to 26.8%, moderate AD changed from 26.5% to 29.1%, and severe AD changed from 24.6% to 30.7%. Conclusions: The relative distribution of AD severities was stable over time. Accurate prevalence estimation is critical for healthcare resource allocation and facilitating patients receiving innovative medicines.
Pages 1077-1092
Masanori Kurihara, Soichiro Kondo, Kensuke Ohse, Hisashi Nojima, Emiko Kikkawa-Saito, Atsushi Iwata
Relationship Between Cerebrospinal Fluid Alzheimer’s Disease Biomarker Values Measured via Lumipulse Assays and Conventional ELISA: Single-Center Experience and Systematic Review
Abstract: Background: Although Lumipulse assays and conventional ELISA are strongly correlated, the precise relationship between their measured values remains undetermined. Objective: To determine the relationship between Lumipulse and ELISA measurement values. Methods: Patients who underwent cerebrospinal fluid (CSF) Alzheimer’s disease (AD) biomarker measurements and consented to biobanking between December 2021 and June 2023 were included. The relationship between values measured via Lumipulse assays and conventional ELISA were evaluated by Passing-Bablok analyses for amyloid-β 1-42 (Aβ42), total tau (t-tau), and phospho-tau 181 (p-tau 181). Studies using both assays were systematically searched for in PubMed and summarized after quality assessment. Results: Regression line slopes and intercepts were 1.41 (1.23 to 1.60) and -77.8 (-198.4 to 44.5) for Aβ42, 0.94 (0.88 to 1.01) and 98.2 (76.9 to 114.4) for t-tau, and 1.60 (1.43 to 1.75) and -21.1 (-26.9 to -15.6) for p-tau181. Spearman’s correlation coefficients were 0.90, 0.95, and 0.95 for Aβ42, t-tau, and p-tau181, respectively. We identified 13 other studies that included 2,117 patients in total. Aβ42 slope varied among studies, suggesting inter-lab difference of ELISA. The slope and intercept of t-tau were approximately 1 and 0, respectively, suggesting small proportional and systematic differences. Conversely, the p-tau181 slope was significantly higher than 1, distributed between 1.5–2 in most studies, with intercepts significantly lower than 0, suggesting proportional and systematic differences. Conclusions: We characterized different relationship between measurement values for each biomarker, which may be useful for understanding the differences in CSF biomarker measurement values on different platforms and for future global harmonization.
Pages 1093-1104
Jessica J. Zakrzewski, Jennifer D. Davis, Zachary Gemelli, Laura E. Korthauer
Understanding Health Beliefs and Health Behaviors in Older Adults at Risk for Alzheimer’s Disease
Abstract: Background: There are significant public health benefits to delaying the onset of Alzheimer’s disease (AD) in individuals at risk. However, adherence to brain healthy behaviors is low. The Health Belief Model proposes that specific beliefs are mediators of behavior change. Objective: To characterize health belief measures from the Science of Behavior Change Research Network (SBCRN) in an older adult population and associations between health beliefs, AD risk, and current health behaviors. Methods: A total of 172 individuals from the Rhode Island AD Prevention Registry participated. SBCRN health belief measures included assessments of future time perspective, self-efficacy, deferment of gratification, and consideration of future consequences. Outcome measures included individual AD risk index score, dementia risk awareness, and lifestyle behaviors including physical, cognitive, and social activity. Results: Participants who were older had higher scores for AD risk, lower future time perspective, and lower generalized self-efficacy (all at p<0.001). Higher generalized self-efficacy was related to increased physical activity (p<0.010). Higher future time perspective (p<0.001) and generalized self-efficacy (p=0.48) were associated with lower AD risk score. Subjective cognitive decline (SCD) was associated with lower self-efficacy, ability to delay gratification, and a less expansive future time perspective. Conclusions: Greater self-efficacy and perceived future time remaining were associated with lower AD risk and greater engagement in physical activity. SCD was associated with health beliefs that may negatively affect engagement in positive brain health behaviors. Assessment of and psychoeducation about these intrapersonal health belief constructs may be important targets for behavioral interventions to reduce AD risk.
Pages 1105-1115
Brian Downer, Sadaf Milani, Stephanie Grasso, Fernando Llanos Lucas, Neil Mehta
Dual-Language Use and Cognitive Function Among Mexican Americans Aged 65 and Older
Abstract: Background: Better English proficiency and higher frequency of using English among non-native speakers are associated with lower dementia risk. Objective: We investigated if Mexican American older adults who use English and Spanish to a more similar degree demonstrate better cognitive function than those who use one language more than the other. Methods: We used data from waves one (1992/93) to eight (2012/13) of the Hispanic Established Population for the Epidemiological Study of the Elderly. At baseline, participants were asked what language they usually use across communicative contexts. We based dual language on participants' use of Spanish and English within and across contexts. We categorized participants as low (n=1,145), medium (n=717), and high (n=702) dual-language users. Linear mixed models were used to estimate the association between dual-language use, baseline Mini-Mental State Examination (MMSE) scores, and change in MMSE. Results: Participants in the medium and high dual-language use categories scored 1.91 points and 3.03 points higher at wave one compared to the low dual-language use category. Adjusting for education reduced the association between dual-language use and baseline MMSE (medium B=0.99 SE=0.19 p<0.01; high B=1.41 SE=0.21 p<0.01). The association between dual-language use and decline in the MMSE was not statistically significant. Conclusions: Greater dual-language use was associated with higher MMSE scores but not change in MMSE scores among Mexican Americans aged 65 and older. Future work should characterize bilingualism with greater nuance and use more rigorous cognitive measures to identify the components of the bilingual experience that may benefit the cognitive functioning of older adult bilinguals.
Pages 1117-1127
Hasom Moon, Hongki Ham, Jihwan Yun, Daeun Shin, Eun Hye Lee, Hee Jin Kim, Sang Won Seo, Duk L. Na, Hyemin Jang
Prediction of Amyloid Positivity in Patients with Subcortical Vascular Cognitive Impairment
Abstract: Background: Amyloid-β (Aβ) commonly coexists and impacts prognosis in subcortical vascular cognitive impairment (SVCI). Objective: This study aimed to examine the differences in clinical and neuroimaging variables between Aβ-positive and Aβ-negative SVCI and to propose a prediction model for Aβ positivity in clinically diagnosed SVCI patients. Methods: A total of 130 patients with SVCI were included in model development, and a separate cohort of 70 SVCI patients was used in external validation. The variables for the prediction model were selected by comparing the characteristics of the Aβ-negative and Aβ-positive SVCI groups. The final model was determined using a stepwise method. The model performance was evaluated using the receiver operating characteristic (ROC) curve and a calibration curve. A nomogram was used for visualization. Results: Among 130 SVCI patients, 70 (53.8%) were Aβ-positive. The Aβ-positive SVCI group was characterized by older age, tendency to be in the dementia stage, a higher prevalence of APOE ε4, a lower prevalence of lacune, and more severe medial temporal atrophy (MTA). The final prediction model, which excluded MTA grade following the stepwise method for variable selection, demonstrated good accuracy in distinguishing between Aβ-positive and Aβ-negative SVCI, with an area under the curve (AUC) of 0.80. The external validation demonstrated an AUC of 0.71. Conclusions: The findings suggest that older age, dementia stage, APOE ε4 carrier, and absence of lacunes may be predictive of Aβ positivity in clinically diagnosed SVCI patients.
Pages 1129-1145
Simone Gamm, Deborah Ummel, Nancy Vasil, Sébastien Grenier
Getting Insight to the Lived Emotional Experience of People with Alzheimer’s Disease Shortly After Diagnosis: A Phenomenological Approach
Abstract: Background: A diagnosis of Alzheimer's disease (AD) is a crucial moment in an individual’s existence and represents a major life change that often results in psychological distress, diminish of perceived quality of life, and loss of independence. It is important to better understand the emotional experience of people with dementia to intervene according to their specific needs. Objective: The aim of the research was to get insight to the emotional experience of people with AD shortly after its discovery and the consequences thereof. Methods: A qualitative exploratory design was engaged, and in-depth interviews were conducted with ten French-speaking participants over 70 years recently diagnosed. Interviews were guided by Heideggerian phenomenology about movements in the worldview of individuals. The transcribed data was subjected to interpretative phenomenological analysis. Results: Following the diagnosis, participants experienced either shock or denial. Emotions felt were unpleasant and disturbing for most of them. Especially when participants were confronted with news concerning the illness, they experienced incomprehension. They engaged in an oscillatory motion of connection and disconnection to establish new meanings of their worldview. Thinking about the past seemed to diminish their worries, to reinforce the possibility to fulfil a significant place in their existence and to maintain their autonomy. Conclusions: When participants could express their emotional experience and their concerns, they regained a sense of control in their life that seemed du reduce their distress. With this insight, intervention could be adapted to the specific needs of people with AD to enhance their self-determination and quality of life.
Pages 1147-1158
Erica Costantini, Claudia Carrarini, Dario Calisi, Matteo De Rosa, Marianna Simone, Adolfo Di Crosta, Rocco Palumbo, Alessia Cipollone, Lisa Aielli, Maria De Laurentis, Lucilla Colarusso, Andrea Pilotto, Alessandro Padovani, Fani Konstantinidou, Valentina Gatta, Liborio Stuppia, Francesco Cipollone, Marta Di Nicola, Marcella Reale, Laura Bonanni
Search in the Periphery for Potential Inflammatory Biomarkers of Dementia with Lewy Bodies and Alzheimer’s Disease
Abstract: Background: Neuroinflammation, with altered peripheral proinflammatory cytokine production, plays a major role in the pathogenesis of neurodegenerative diseases, such as Alzheimer’s disease (AD), while the role of inflammation in dementia with Lewy bodies (DLB) is less known and the results of different studies are often in disagreement. Objective: The present study aimed to investigate the levels of TNFα and IL-6 in serum and supernatants, and the related DNA methylation in patients affected by DLB and AD compared to healthy controls (HCs), to clarify the role of epigenetic mechanisms of DNA promoter methylation on of pro-inflammatory cytokines overproduction. Methods: Twenty-one patients with DLB and fourteen with AD were frequency-matched for age and sex with eleven HCs. Clinical evaluation, TNFα and IL-6 gene methylation status, cytokine gene expression levels and production in serum and peripheral blood mononuclear cell (PBMC) supernatants were performed. Results: In AD and DLB patients, higher serum levels of IL-6 and TNFα were detected than in HCs. Differences in LPS-stimulated versus spontaneous PBMCs were observed between DLB, AD, and HC in the levels of TNFα (p=0.027) and IL-6 (p<0.001). Higher levels were also revealed for sIL-6R in DLB (p<0.001) and AD (p<0.001) in comparison with HC.DNA hypomethylation in IL-6 and TNFα CpG promoter sites was detected for DLB and AD patients compared to the corresponding site in HCs. Conclusions: Our preliminary study documented increased levels of IL-6 and TNFα in DLB and AD patients to HCs. This overproduction can be due to epigenetic mechanisms regarding the hypomethylation of DNA promoters.
