Challenges of multimorbidity of the aging brain: a critical update

α-Synuclein: A Promising Biomarker for Parkinson's Disease and Related Disorders

Mutations in the SNCA gene, which encodes α-synuclein (α-syn), play a key role in the development of genetic Parkinson's disease (PD). α-Syn is a major component of Lewy bodies in PD and glial cytoplasmic inclusions in multiple system atrophy (MSA). Rapid eye movement sleep behavior disorder patients often progress to PD, dementia with Lewy bodies, or MSA, which are collectively known as α-synucleinopathies. The loss of dopaminergic neurons with Lewy bodies precedes motor dysfunction in these diseases, but the mechanisms of neurodegeneration due to α-syn aggregation are poorly understood. Monitoring α-syn aggregation in vivo could serve as a diagnostic biomarker and help elucidate pathogenesis, necessitating a simple and accurate detection method. Seed amplification assays (SAAs), such as real-time quaking-induced conversion and protein misfolding cyclic amplification, are used to detect small amounts of abnormally structured α-syn protofibrils, which are central to aggregation. These methods are promising for the early diagnosis of α-synucleinopathy. Differences in α-syn filament structures between α-synucleinopathies, as observed through transmission electron microscopy and cryo-electron microscopy, suggest their role in the pathogenesis of neurodegeneration. SAAs may differentiate between subtypes of α-synucleinopathy and other diseases. Efforts are also being made to identify α-syn from blood using various methods. This review introduces body fluid α-syn biomarkers based on pathogenic α-syn seeds, which are expected to redefine α-synucleinopathy diagnosis and staging, improving clinical research accuracy and facilitating biomarker development.

Age-Related Pathology in Corticobasal Degeneration

Elderly human brains are vulnerable to multiple proteinopathies, although each protein has a different transmission pathway. Tau-immunoreactive astrocytes are well-known in elderly brains. In contrast, astrocytic plaques, a hallmark in corticobasal degeneration (CBD), rarely occur in aging and neurodegenerative disease other than CBD. To elucidate the clinicopathological correlation of aging-related pathology in CBD, we examined 21 pathologically proven CBD cases in our institute (12 males and 9 females, with a mean age of death 70.6 years). All CBD cases showed grains and neurofibrillary tangles (NFTs). Fifteen cases (71.4%) showed beta-amyloid deposition such as senile plaques or cerebral amyloid angiopathy. Three cases (14.3%) had Lewy body pathology. One case was classified as amygdala-predominant Lewy body disease, although no cases met the pathological criteria for Alzheimer's disease. Five cases (23.8%) displayed Limbic-predominant and age-related TDP-43 encephalopathy (LATE). NFTs, grains, and TDP-43-positive neuronal inclusions were widely distributed throughout the limbic system of CBD patients, but their densities were low. CBD might a have similar cell vulnerability and transmission pathway to that of multiple proteinopathy in aging brains.

Network Proteomics of the Lewy Body Dementia Brain Reveals Presynaptic Signatures Distinct from Alzheimer's Disease

Lewy body dementia (LBD), a class of disorders comprising Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB), features substantial clinical and pathological overlap with Alzheimer's disease (AD). The identification of biomarkers unique to LBD pathophysiology could meaningfully advance its diagnosis, monitoring, and treatment. Using quantitative mass spectrometry (MS), we measured over 9,000 proteins across 138 dorsolateral prefrontal cortex (DLPFC) tissues from a University of Pennsylvania autopsy collection comprising control, Parkinson's disease (PD), PDD, and DLB diagnoses. We then analyzed co-expression network protein alterations in those with LBD, validated these disease signatures in two independent LBD datasets, and compared these findings to those observed in network analyses of AD cases. The LBD network revealed numerous groups or "modules" of co-expressed proteins significantly altered in PDD and DLB, representing synaptic, metabolic, and inflammatory pathophysiology. A comparison of validated LBD signatures to those of AD identified distinct differences between the two diseases. Notably, synuclein-associated presynaptic modules were elevated in LBD but decreased in AD relative to controls. We also found that glial-associated matrisome signatures consistently elevated in AD were more variably altered in LBD, ultimately stratifying those LBD cases with low versus high burdens of concurrent beta-amyloid deposition. In conclusion, unbiased network proteomic analysis revealed diverse pathophysiological changes in the LBD frontal cortex distinct from alterations in AD. These results highlight the LBD brain network proteome as a promising source of biomarkers that could enhance clinical recognition and management.

Use of adapted or modified methods with people with dementia in research: A scoping review

People with dementia are excluded from research due to methodological challenges, stigma, and discrimination. Including perspectives of people with dementia across a spectrum of abilities is essential to understanding their perspectives and experiences. Engaging people living with dementia in qualitative research can require adaptation of methods.Qualitative research is typically considered when researchers seek to understand the perspectives, lived experiences, or opinions of individuals' social reality. This scoping review explores current use of adapted methods with people with dementia in qualitative research, including methods used and impacts on the engagement as it relates to meeting accessibility needs. This review considered rationales for adaptations provided by authors, particularly whether authors identified a human rights or justice rationale for adapting methods to promote accessibility and engagement.This review began with a search of primary studies using qualitative research methods published in English in OECD countries from 2017 to 2022. Two reviewers screened titles and abstracts for inclusion. Full texts were reviewed, and data from included studies were extracted using a pre-determined chart. Content analysis of rationales was conducted and reviewed by all authors. Studies were assessed for findings related to impacts of adapted methods.Twenty-eight studies met inclusion criteria. Adaptations to qualitative research methods ranged from minor changes, such as maintaining a familiar interviewer, to more extensive novel methods such as photo-elicitation techniques. Twenty-seven studies provided a rationale for adapting their methods. No studies assessed impacts of their methodology on engagement or accessibility. Five studies observed that their methodology supported engagement.This review helps understand the breadth of adaptations that researchers have made to qualitative research methods to include people with dementia in research. Research is needed to explore adaptations and their impact on engagement of persons with dementia with a range of abilities and backgrounds.

Neurodegenerative pathologies associated with behavioral and psychological symptoms of dementia in a community-based autopsy cohort

In addition to the memory disorders and global cognitive impairment that accompany neurodegenerative diseases, behavioral and psychological symptoms of dementia (BPSD) commonly impair quality of life and complicate clinical management. To investigate clinical-pathological correlations of BPSD, we analyzed data from autopsied participants from the community-based University of Kentucky Alzheimer's Disease Research Center longitudinal cohort (n = 368 research volunteers met inclusion criteria, average age at death 85.4 years). Data assessing BPSD were obtained approximately annually, including parameters for agitation, anxiety, apathy, appetite problems, delusions, depression, disinhibition, hallucinations, motor disturbance, and irritability. Each BPSD was scored on a severity scale (0-3) via the Neuropsychiatric Inventory Questionnaire (NPI-Q). Further, Clinical Dementia Rating (CDR)-Global and -Language evaluations (also scored on 0-3 scales) were used to indicate the degree of global cognitive and language impairment. The NPI-Q and CDR ratings were correlated with neuropathology findings at autopsy: Alzheimer's disease neuropathological changes (ADNC), neocortical and amygdala-only Lewy bodies (LBs), limbic predominant age-related TDP-43 encephalopathy neuropathologic changes (LATE-NC), primary age-related tauopathy (PART), hippocampal sclerosis, and cerebrovascular pathologies. Combinations of pathologies included the quadruple misfolding proteinopathy (QMP) phenotype with co-occurring ADNC, neocortical LBs, and LATE-NC. Statistical models were used to estimate the associations between BPSD subtypes and pathologic patterns. Individuals with severe ADNC (particularly those with Braak NFT stage VI) had more BPSD, and the QMP phenotype was associated with the highest mean number of BPSD symptoms: > 8 different BPSD subtypes per individual. Disinhibition and language problems were common in persons with severe ADNC but were not specific to any pathology. "Pure" LATE-NC was associated with global cognitive impairment, apathy, and motor disturbance, but again, these were not specific associations. In summary, Braak NFT stage VI ADNC was strongly associated with BPSD, but no tested BPSD subtype was a robust indicator of any particular "pure" or mixed pathological combination.

A systematic review of randomised-controlled trials on deprescribing outcomes in older adults with polypharmacy

BACKGROUND

Mixed findings about deprescribing impact have emerged from varied study designs, interventions, outcome measures and targeting sub-categories of medications or morbidities. This systematic review controls for study design by reviewing randomised-controlled trials (RCTs) of deprescribing interventions using comprehensive medication profiles. The goal is to provide a synthesis of interventions and patient outcomes to inform healthcare providers and policy makers about deprescribing effectiveness.

OBJECTIVES

This systematic review aims to (1) review RCT deprescribing studies focusing on complete medication reviews of older adults with polypharmacy across all health settings, (2) map patients' clinical and economic outcomes against intervention and implementation strategies and (3) inform research agendas based on observed benefits and best practices.

METHODS

The PRISMA framework for systematic reviews was followed. Databases used were EBSCO Medline, PubMed, Cochrane Library, Scopus and Web of Science. Risk of bias was assessed using the Cochrane Risk of Bias tool for randomised trials.

RESULTS

Fourteen articles were included. Interventions varied in setting, preparation, use of interdisciplinary teams, validated guidelines and tools, patient-centredness and implementation strategy. Thirteen studies (92.9%) found deprescribing interventions reduced the number of drugs and/or doses taken. No studies found threats to patient safety in terms of primary outcomes including morbidity, hospitalisations, emergency room use and falls. Four of five studies identifying health quality of life as a primary outcome found significant effects associated with deprescribing. Both studies with cost as their primary outcome found significant effects as did two with cost as a secondary outcome. Studies did not systematically study how intervention components influenced deprescribing impact. To explore this gap, this review mapped studies' primary outcomes to deprescribing intervention components using the Consolidated Framework for Implementation Research. Five studies had significant, positive primary outcomes related to health-related quality of life (HRQOL), cost and/or hospitalisation, with four reporting patient-centred elements in their intervention.

CONCLUSIONS

RCT primary outcomes found deprescribing is safe and reduces drug number or dose. Five RCTs found a significant deprescribing impact on HRQOL, cost or hospitalisation. Important future research agendas include analysing (1) understudied outcomes like cost, and (2) intervention and implementation components that enhance effectiveness, such as patient-centred elements.

Clinical relevance of animal models in aging-related dementia research

Alzheimer's disease (AD) and other, less prevalent dementias are complex age-related disorders that exhibit multiple etiologies. Over the past decades, animal models have provided pathomechanistic insight and evaluated countless therapeutics; however, their value is increasingly being questioned due to the long history of drug failures. In this Perspective, we dispute this criticism. First, the utility of the models is limited by their design, as neither the etiology of AD nor whether interventions should occur at a cellular or network level is fully understood. Second, we highlight unmet challenges shared between animals and humans, including impeded drug transport across the blood-brain barrier, limiting effective treatment development. Third, alternative human-derived models also suffer from the limitations mentioned above and can only act as complementary resources. Finally, age being the strongest AD risk factor should be better incorporated into the experimental design, with computational modeling expected to enhance the value of animal models.

Assessment of Joint and Interactive Effects of Multimorbidity and Chronic Pain on ADRD Risk in the Elder Population

Objective

Multimorbidity and non-cancer chronic pain conditions (NCPC) are independently linked to elevated risk for cognitive impairment and incident Alzheimer's Disease and Related Dementias (ADRD)-both - We present the study of potential joint and interactive effects of these conditions on the risk of incident ADRD in older population.

Methods

This retrospective-cohort study drew baseline and 2-year follow-up data from linked Medicare claims and Medicare Current Beneficiary Survey (MCBS). Baseline multimorbidity and NCPC were ascertained using claims data. ADRD was ascertained at baseline and follow-up.

Results

NCPC accompanied by multimorbidity (vs. absence of NCPC or multimorbidity) had a significant and upward association with incident ADRD (adjusted odds ratio (AOR): 1.72, 95% CI 1.38, 2.13, p < 0.0001). Secondary analysis by number of comorbid conditions suggested that the joint effects of NCPC and multimorbidity on ADRD risk may increase with rising number contributing chronic conditions. Interaction analyses indicated significantly elevated excess risk for incident ADRD.

Association between amyloid-beta deposition and cortical thickness in dementia with Lewy bodies

OBJECTIVE

Amyloid-beta often co-exists in dementia with Lewy bodies, but its clinical relevance in dementia with Lewy bodies remains unclear. This study aimed to investigate the clinical and imaging correlates of amyloid-beta deposition in dementia with Lewy bodies, particularly its relationship with cortical thickness in Alzheimer's disease-prone regions and hippocampal volume.

METHODS

Twenty-four participants with probable dementia with Lewy bodies underwent high-resolution magnetic resonance imaging and amyloid-beta positron emission tomography imaging using the radiotracer ¹⁸F-NAV4694. Amyloid-beta deposition was quantified and reported using the Centiloid method.

RESULTS

Amyloid-beta positivity, defined as Centiloid > 50, was present in 45.8% of dementia with Lewy bodies participants. There were no statistically significant differences in clinical characteristics between Aβ+ and Aβ- dementia with Lewy bodies. Compared with the Aβ- group, Aβ+ dementia with Lewy bodies exhibited greater global cortical thinning as well as in the Alzheimer's disease-prone region of interest, adjusted for age, sex and years of education. A mean cortical thickness of 5.12 mm across a combined meta-region of interest has a sensitivity of 88.9% and specificity of 90.0% in discriminating Aβ+ from Aβ- dementia with Lewy bodies. Hippocampal volume was not different between groups.

CONCLUSION

Early structural changes in cortical thickness, but not hippocampal volume, were observed in dementia with Lewy bodies with significant amyloid-beta burden. This may represent an early Alzheimer's disease-related neurodegenerative process.

Predicting Cognitive Decline in Older Adults Using Baseline Metrics of AD Pathologies, Cerebrovascular Disease, and Neurodegeneration

BACKGROUND AND OBJECTIVES

Dementia is a growing socioeconomic challenge that requires early intervention. Identifying biomarkers that reliably predict clinical progression early in the disease process would better aid selection of individuals for future trial participation. Here, we compared the ability of baseline, single time-point biomarkers (CSF amyloid 1-42, CSF ptau-181, white matter hyperintensities (WMH), cerebral microbleeds, whole-brain volume, and hippocampal volume) to predict decline in cognitively normal individuals who later converted to mild cognitive impairment (MCI) (CNtoMCI) and those with MCI who later converted to an Alzheimer disease (AD) diagnosis (MCItoAD).

METHODS

Standardized baseline biomarker data from AD Neuroimaging Initiative 2 (ADNI2)/GO and longitudinal diagnostic data (including ADNI3) were used. Cox regression models assessed biomarkers in relation to time to change in clinical diagnosis using all follow-up time points available. Models were fit for biomarkers univariately and together in a multivariable model. Hazard ratios (HRs) were compared to evaluate biomarkers. Analyses were performed separately in CNtoMCI and MCItoAD groups.

RESULTS

For CNtoMCI (n = 189), there was strong evidence that higher WMH volume (individual model: HR 1.79, p = 0.002; fully adjusted model: HR 1.98, p = 0.003) and lower hippocampal volume (individual: HR 0.54, p = 0.001; fully adjusted: HR 0.40, p < 0.001) were associated with conversion to MCI individually and independently. For MCItoAD (n = 345), lower hippocampal (individual model: HR 0.45, p < 0.001; fully adjusted model: HR 0.55, p < 0.001) and whole-brain volume (individual: HR 0.31, p < 0.001; fully adjusted: HR 0.48, p = 0.02), increased CSF ptau (individual: HR 1.88, p < 0.001; fully adjusted: HR 1.61, p < 0.001), and lower CSF amyloid (individual: HR 0.37, p < 0.001; fully adjusted: HR 0.62, p = 0.008) were most strongly associated with conversion to AD individually and independently.

DISCUSSION

Lower hippocampal volume was a consistent predictor of clinical conversion to MCI and AD. CSF and brain volume biomarkers were predictive of conversion to AD from MCI, whereas WMH were predictive of conversion to MCI from cognitively normal. The predictive ability of WMH in the CNtoMCI group may be interpreted as some being on a different pathologic pathway, such as vascular cognitive impairment.

Cognitive Trajectories and Associated Biomarkers in Patients with Mild Cognitive Impairment

BACKGROUND

To diagnose mild cognitive impairment (MCI) patients at risk of progression to dementia is clinically important but challenging.

OBJECTIVE

We classified MCI patients based on cognitive trajectories and compared biomarkers among groups.

METHODS

This study analyzed amnestic MCI patients with at least three Clinical Dementia Rating (CDR) scores available over a minimum of 36 months from the Alzheimer's Disease Neuroimaging Initiative database. Patients were classified based on their progression using trajectory modeling with the CDR-sum of box scores. We compared clinical and neuroimaging biomarkers across groups.

RESULTS

Of 569 eligible MCI patients (age 72.7±7.4 years, women n = 223), three trajectory groups were identified: stable (58.2%), slow decliners (24.6%), and fast decliners (17.2%). In the fifth year after diagnosis, the CDR-sum of box scores increased by 1.2, 5.4, and 11.8 points for the stable, slow, and fast decliners, respectively. Biomarkers associated with cognitive decline were amyloid-β 42, total tau, and phosphorylated tau protein in cerebrospinal fluid, hippocampal volume, cortical metabolism, and amount of cortical and subcortical amyloid deposits. Cortical metabolism and the amount of amyloid deposits were associated with the rate of cognitive decline.

CONCLUSION

Data-driven trajectory analysis provides new insights into the various cognitive trajectories of MCI. Baseline brain metabolism, and the amount of cortical and subcortical amyloid burden can provide additional information on the rate of cognitive decline.

Association of Stroke and Cerebrovascular Pathologies With Scam Susceptibility in Older Adults

Importance

Scam susceptibility is associated with adverse financial and health outcomes, including an increased risk of cognitive decline and dementia. Very little is known about the role of cerebrovascular pathologies with scam susceptibility.

Objective

To examine the association of diverse cerebrovascular pathologies (globally and regionally) with scam susceptibility.

Design, setting, and Participants

This clinical-pathological cohort study included participants from 2 ongoing studies of aging that began enrollment in 1994 and 1997. In 2010, participants were enrolled in the decision-making and behavioral economics substudy and were followed up for a mean (SD) of 3.4 (2.6) years prior to death. From 1365 older persons with clinical evaluations, 69 were excluded for having dementia at baseline. From 538 older persons who died, 408 had annual assessments for scam susceptibility, cardiovascular risk burden, and cognitive function and consented to brain donation for detailed neuropathologic examination. Data were analyzed from June 2021 through September 2022.

Exposures

Neuropathologic examination identified the presence of macroscopic and microscopic infarcts, atherosclerosis, arteriolosclerosis, cerebral amyloid angiopathy, and common neurodegenerative pathologies (Alzheimer disease, limbic-predominant age-related transactive response DNA-binding protein 43 encephalopathy, and Lewy bodies).

Results

There was a total of 408 participants. The mean (SD) age at death was 91 (6.1) years, the mean (SD) amount of education was 15.6 (3.1) years, and 297 (73%) were women. Participants included 4 Latino individuals (1%), 7 non-Latino Black individuals (2%), and 397 non-Latino White individuals (97%). The frequency of participants with macroscopic infarcts was 38% (n = 154), microinfarcts was 40% (n = 163), and moderate to severe vessel disease; specifically, atherosclerosis was 20% (n = 83), arteriolosclerosis was 25% (n = 100), and cerebral amyloid angiopathy was 35% (n = 143). In linear regression models adjusted for demographics and neurodegenerative pathologies, macroscopic infarcts were associated with greater scam susceptibility (estimate [SE], 0.18 [0.07]; P = .009). This association persisted after adjusting for cardiovascular risk burden and global cognition. Regionally, infarcts localized to the frontal, temporal, and occipital lobes and thalamus were associated with greater scam susceptibility. Neither arteriosclerosis, atherosclerosis, cerebral amyloid angiopathy, nor microinfarcts were associated with scam susceptibility.

Conclusions and Relevance

Cerebrovascular pathologies, specifically cerebral infarcts, is linked with greater scam susceptibility in older adults, independent of common neurodegenerative diseases such as Alzheimer disease. Future studies examining in vivo magnetic resonance imaging markers of cerebrovascular pathologies with scam susceptibility and related decision-making outcomes will be important.

Neuropathological lesions and their contribution to dementia and cognitive impairment in a heterogeneous clinical population

INTRODUCTION

Alzheimer disease (AD) and related dementias are characterized by damage caused by neuropathological lesions in the brain. These include AD lesions (plaques and tangles) and non-AD lesions such as vascular injury or Lewy bodies. We report here an assessment of lesion association to dementia in a large clinic-based population.

METHODS

We identified 5272 individuals with neuropathological data from the National Alzheimer's Coordinating Center. Individual lesions, as well as a neuropathological composite score (NPCS) were tested for association with dementia, and both functional and neurocognitive impairment using regression models.

RESULTS

Most individuals exhibited mixed pathologies, especially AD lesions in combination with non-AD lesions. All lesion types were associated with one or more clinical outcomes; most even while controlling for AD pathology. The NPCS was also associated with clinical outcomes.

DISCUSSION

These data suggest mixed-type pathologies are extremely common in a clinic-based population and may contribute to dementia and cognitive impairment.

Association of Cognition and Dementia With Neuropathologic Changes of Alzheimer Disease and Other Conditions in the Oldest Old

BACKGROUND AND OBJECTIVES

Age is the largest risk factor for dementia. However, dementia is not universal, even among the oldest-old age groups. Following contemporary neuropathologic guidelines, our objectives were to describe the key neuropathologic lesions and their associations with antemortem cognition in oldest-old individuals.

METHODS

Participants were those enrolled in The 90+ Study, a longitudinal, population-based study of aging/dementia in the oldest old, who agreed to postmortem brain examination. All autopsied brains as of December 2020 were evaluated for the prevalence of Alzheimer disease neuropathologic change (ADNC) and non-ADNC neuropathologic comorbidities. Associations between neuropathologic lesions or the total neuropathologic burden score (sum of the individual scores) and cognition were assessed using multinomial logistic regression and multiple linear regression. Separate regression analyses evaluated relationships between limbic-predominant age-related TDP-43 encephalopathy (LATE-NC) and hippocampal sclerosis (HS) or ADNC/primary age-related tauopathy (PART). Resistance, or failure to develop ADNC/PART, and resilience, inferred from higher-than-expected cognitive functioning, were evaluated in the presence or absence of non-ADNC neuropathologic features.

RESULTS

The most common neuropathologic features in the sample (n = 367) were ADNC/PART related. Increased dementia odds were associated with elevated total neuropathologic burden (odds ratio [OR] 1.5, 95% CI 1.3-1.7, p < 0.0001), β-amyloid (OR 1.6, 95% CI 1.2-2.0, p < 0.0001), neurofibrillary tangles (OR 2.6, 95% CI 1.7-4.1, p < 0.0001), and LATE-NC (OR 2.3, 95% CI 1.7-3.1, p < 0.0001), correcting for multiple comparisons. LATE-NC was associated with dementia with (OR 6.1, 95% CI 2.0-18.7, p = 0.002) and without (OR 5.0, 95% CI 2.6-9.7, p < 0.0001) co-occurring HS and increased the odds of dementia among participants with ADNC (OR 5.0, 95% CI 2.7-9.2, p < 0.0001). Resistance to moderate/severe ADNC/PART was rare (3%), but resilience to ADNC/PART was not (55%). Resilience was rarer in the presence of non-ADNC comorbid lesions, particularly LATE-NC. Among those with moderate/severe ADNC/PART, dementia odds increased with each non-ADNC comorbid lesion (e.g., 1 lesion: OR 2.4, 95% CI 1.3-4.5, p < 0.005; 2 lesions: OR 5.9, 95% CI 2.8-12.3, p < 0.0001).

DISCUSSION

These results highlight the importance of non-ADNC neuropathologic comorbidity, predominantly LATE-NC, to cognition in the oldest old. Given the cumulative effects of non-ADNC comorbid neuropathologic abnormalities, reducing their prevalence, especially LATE-NC, will be vital to the ultimate goal of reducing dementia burden in the oldest-old individuals.

Poststroke Cognitive Impairment: A Longitudinal Follow-Up and Pre/Poststroke Mini-Mental State Examination Comparison

BACKGROUND

Poststroke cognitive impairment (PSCI) is a prevalent cause of disability in people with stroke. PSCI results from either lesion-dependent loss of cognitive function or augmentation of Alzheimer's pathology due to vascular insufficiency. The lack of prestroke cognitive assessments limits the clear understanding of the impact of PSCI on cognition.

OBJECTIVE

The present study aims to make a direct comparison of longitudinal cognitive assessment results to clarify the impact of ischemic stroke on PSCI and assess the cognitive decline in PSCI compared to people with Alzheimer's disease (AD).

METHODS

All study participants had their Mini-Mental State Examination (MMSE) at the chronic poststroke stage (≥6 months after stroke), which was compared with prestroke or acute poststroke (<6 months after stroke) MMSE to investigate the two aspects of PSCI. A group of patients with AD was used to reference the speed of neurodegenerative cognitive deterioration. Repeated measures analysis of variance was used to compare the longitudinal change of MMSE.

RESULTS

MMSE score between acute and chronic poststroke revealed a 1.8 ± 6.49 decline per year (n=76), which was not significantly different from the AD patients who underwent cholinesterase inhibitors treatment (-1.11 ± 2.61, p=0.35, n=232). MMSE score between prestroke and chronic poststroke (n=33) revealed a significant decline (-6.52 ± 6.86, p < 0.001). In addition, their cognitive deterioration was significantly associated with sex, age, and stroke over the white matter or basal ganglia.

CONCLUSION

Ischemic stroke substantially affects cognition with an average six-point drop in MMSE. The rate of cognitive decline in PSCI was similar to AD, and those with white matter or basal ganglia infarct were at greater risk of PSCI.

Current concepts of mixed pathologies in neurodegenerative diseases

Neurodegenerative diseases are a pathologically, clinically and genetically diverse group of disorders without effective disease-modifying therapies. Pathologically, these disorders are characterised by disease-specific protein aggregates in neurons and/or glia and referred to as proteinopathies. Many neurodegenerative diseases show pathological overlap with the same abnormally deposited protein occurring in anatomically distinct regions, which give rise to specific patterns of cognitive and motor clinical phenotypes. Sequential distribution patterns of protein inclusions throughout the brain have been described. Rather than occurring in isolation, it is increasingly recognised that combinations of one or more proteinopathies with or without cerebrovascular disease frequently occur in individuals with neurodegenerative diseases. In addition, complex constellations of ageing-related and incidental pathologies associated with tau, TDP-43, Aβ, α-synuclein deposition have been commonly reported in longitudinal ageing studies. This review provides an overview of current classification of neurodegenerative and age-related pathologies and presents the spectrum and complexity of mixed pathologies in community-based, longitudinal ageing studies, in major proteinopathies, and genetic conditions. Mixed pathologies are commonly reported in individuals >65 years with and without cognitive impairment; however, they are increasingly recognised in younger individuals (<65 years). Mixed pathologies are thought to lower the threshold for developing cognitive impairment and dementia. Hereditary neurodegenerative diseases also show a diverse range of mixed pathologies beyond the proteinopathy primarily linked to the genetic abnormality. Cases with mixed pathologies might show a different clinical course, which has prognostic relevance and obvious implications for biomarker and therapy development, and stratifying patients for clinical trials.

Association of small vessel disease with tau pathology

Emerging evidence suggests that small vessel disease (SVD) is a risk factor for clinical dementia and may contribute to AD neuropathological changes. Watershed brain regions are located at the most distal areas between arterial territories, making them vulnerable to SVD-related changes. We examined the association of pathologic markers of SVD, specifically arteriolosclerosis in watershed brain regions, with AD pathologic changes. Participants (N = 982; mean age-at-death = 90; 69% women) were enrolled as part of one of two cohort studies of aging and dementia. At autopsy, neuropathological evaluation included semi-quantitative grading of arteriolosclerosis pathology from 2 cortical watershed regions: the anterior watershed (AWS) and posterior watershed (PWS), densities for cortical β-amyloid and tau-tangle pathology, and other common age-related pathologies. Linear regression models examined the association of watershed arteriolosclerosis pathology with β-amyloid and tau-tangle burden. In follow-up analyses, available ex-vivo MRI and proteomics data in a subset of decedents were leveraged to examine the association of whole brain measure of WMH, as a presumed MRI marker of SVD, with β-amyloid and tau-tangle burden, as well as to examine the association of watershed arteriolosclerosis with proteomic tau. Watershed arteriolosclerosis was common, with 45% of older persons having moderate-to-severe arteriolosclerosis pathology in the AWS region, and 35% in the PWS. In fully adjusted models that controlled for demographics and common age-related pathologies, an increase in severity of PWS arteriolosclerosis was associated with a higher burden of tau-tangle burden, specifically neocortical tau burden, but not with β-amyloid. AWS arteriolosclerosis was not associated with β-amyloid or tau pathology. Ex-vivo WMH was associated with greater tau-tangle pathology burden but not β-amyloid. Furthermore, PWS arteriolosclerosis was associated with higher abundance of tau phosphopeptides, that promote formation of tau aggregates. These data provide compelling evidence that SVD, specifically posterior watershed arteriolosclerosis pathology, is linked with tau pathological changes in the aging brain.

Differential protein expression in the hippocampi of resilient individuals identified by digital spatial profiling

Clinical symptoms correlate with underlying neurodegenerative changes in the vast majority of people. However, an intriguing group of individuals demonstrate neuropathologic changes consistent with Alzheimer disease (AD) yet remain cognitively normal (termed “resilient”). Previous studies have reported less overall neuronal loss, less gliosis, and fewer comorbidities in these individuals. Herein, NanoString GeoMx™ Digital Spatial Profiler (DSP) technology was utilized to investigate protein expression differences comparing individuals with dementia and AD neuropathologic change to resilient individuals. DSP allows for spatial analysis of protein expression in multiple regions of interest (ROIs) on formalin-fixed paraffin-embedded sections. ROIs in this analysis were hippocampal neurofibrillary tangle (NFT)-bearing neurons, non-NFT-bearing neurons, and their immediate neuronal microenvironments. Analyses of 86 proteins associated with CNS cell-typing or known neurodegenerative changes in 168 ROIs from 14 individuals identified 11 proteins displaying differential expression in NFT-bearing neurons of the resilient when compared to the demented (including APP, IDH1, CD68, GFAP, SYP and Histone H3). In addition, IDH1, CD68, and SYP were differentially expressed in the environment of NFT-bearing neurons when comparing resilient to demented. IDH1 (which is upregulated under energetic and oxidative stress) and PINK1 (which is upregulated in response to mitochondrial dysfunction and oxidative stress) both displayed lower expression in the environment of NFT-bearing neurons in the resilient. Therefore, the resilient display less evidence of energetic and oxidative stress. Synaptophysin (SYP) was increased in the resilient, which likely indicates better maintenance of synapses and synaptic connections. Furthermore, neurofilament light chain (NEFL) and ubiquitin c-terminal hydrolase (Park5) were higher in the resilient in the environment of NFTs. These differences all suggest healthier intact axons, dendrites and synapses in the resilient. In conclusion, resilient individuals display protein expression patterns suggestive of an environment containing less energetic and oxidative stress, which in turn results in maintenance of neurons and their synaptic connections.

Deep phenotyping of Alzheimer's disease leveraging electronic medical records identifies sex-specific clinical associations

Alzheimer's Disease (AD) is a neurodegenerative disorder that is still not fully understood. Sex modifies AD vulnerability, but the reasons for this are largely unknown. We utilize two independent electronic medical record (EMR) systems across 44,288 patients to perform deep clinical phenotyping and network analysis to gain insight into clinical characteristics and sex-specific clinical associations in AD. Embeddings and network representation of patient diagnoses demonstrate greater comorbidity interactions in AD in comparison to matched controls. Enrichment analysis identifies multiple known and new diagnostic, medication, and lab result associations across the whole cohort and in a sex-stratified analysis. With this data-driven method of phenotyping, we can represent AD complexity and generate hypotheses of clinical factors that can be followed-up for further diagnostic and predictive analyses, mechanistic understanding, or drug repurposing and therapeutic approaches.

Different cardiovascular risk factors are related to distinct white matter hyperintensity MRI phenotypes in older adults

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White matter hyperintensity (WMH) shape: a novel, advanced MRI marker.

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Hypertension correlates with a more irregular shape of periventricular/confluent WMH.

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Different cardiovascular/pathological mechanisms lead to distinct WMH MRI phenotypes.

The underlying mechanisms of the association between cardiovascular risk factors and a higher white matter hyperintensity (WMH) burden are unknown. We investigated the association between cardiovascular risk factors and advanced WMH markers in 155 non-demented older adults (mean age: 71 ± 5 years). The association between cardiovascular risk factors and quantitative MRI-based WMH shape and volume markers were examined using linear regression analysis. Presence of hypertension was associated with a more irregular shape of periventricular/confluent WMH (convexity (B (95 % CI)): −0.12 (−0.22–−0.03); concavity index: 0.06 (0.02–0.11)), but not with total WMH volume (0.22 (−0.15–0.59)). Presence of diabetes was associated with deep WMH volume (0.89 (0.15–1.63)). Body mass index or hyperlipidemia showed no association with WMH markers. In conclusion, different cardiovascular risk factors seem to be related to a distinct pattern of WMH shape markers in non-demented older adults. These findings may suggest that different underlying cardiovascular pathological mechanisms lead to different WMH MRI phenotypes, which may be valuable for early detection of individuals at risk for stroke and dementia.

The pathobiological basis of depression in Parkinson disease: challenges and outlooks

Depression, with an estimated prevalence of about 40% is a most common neuropsychiatric disorder in Parkinson disease (PD), with a negative impact on quality of life, cognitive impairment and functional disability, yet the underlying neurobiology is poorly understood. Depression in PD (DPD), one of its most common non-motor symptoms, can precede the onset of motor symptoms but can occur at any stage of the disease. Although its diagnosis is based on standard criteria, due to overlap with other symptoms related to PD or to side effects of treatment, depression is frequently underdiagnosed and undertreated. DPD has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, in particular dysfunction of neurotransmitter systems (dopaminergic, serotonergic and noradrenergic), as well as to disturbances of cortico-limbic, striato-thalamic-prefrontal, mediotemporal-limbic networks, with disruption in the topological organization of functional mood-related, motor and other essential brain network connections due to alterations in the blood-oxygen-level-dependent (BOLD) fluctuations in multiple brain areas. Other hypothetic mechanisms involve neuroinflammation, neuroimmune dysregulation, stress hormones, neurotrophic, toxic or metabolic factors. The pathophysiology and pathogenesis of DPD are multifactorial and complex, and its interactions with genetic factors, age-related changes, cognitive disposition and other co-morbidities awaits further elucidation.

Histopathological Analysis of Cerebrovascular Lesions Associated With Aging

Cerebrovascular disease (CVD) has been associated with cognitive impairment. Yet, our understanding of vascular contribution to cognitive decline has been limited by heterogeneity of definitions and assessment, as well as its occurrence in cognitively healthy aging. Therefore, we aimed to establish the natural progression of CVD associated with aging. We conducted a retrospective observational study of 63 cognitively healthy participants aged 19-84 years selected through the histological archives of the CHU de Québec. Assessment of CVD lesions was performed independently by 3 observers blinded to clinical data using the Vascular Cognitive Impairment Neuropathology Guidelines (VCING). We found moderate to almost perfect interobserver agreement for most regional CVD scores. Atherosclerosis (ρ = 0.758) and arteriolosclerosis (ρ = 0.708) showed the greatest significant association with age, followed by perivascular hemosiderin deposits (ρ = 0.432) and cerebral amyloid angiopathy (CAA; ρ = 0.392). Amyloid and tau pathologies were both associated with higher CVD load, but only CAA remained significantly associated with amyloid plaques after controlling for age. Altogether, these findings support the presence of multiple CVD lesions in the brains of cognitively healthy adults, the burden of which increases with age and can be quantified in a reproducible manner using standardized histological scales such as the VCING.

The Clinical and Neuropathological Features of Sporadic (Late-Onset) and Genetic Forms of Alzheimer's Disease

The purpose of this review is to compare and highlight the clinical and pathological aspects of genetic versus acquired Alzheimer's disease: Down syndrome-associated Alzheimer's disease in (DSAD) and Autosomal Dominant Alzheimer's disease (ADAD) are compared with the late-onset form of the disease (LOAD). DSAD and ADAD present in a younger population and are more likely to manifest with non-amnestic (such as dysexecutive function features) in the prodromal phase or neurological features (such as seizures and paralysis) especially in ADAD. The very large variety of mutations associated with ADAD explains the wider range of phenotypes. In the LOAD, age-associated comorbidities explain many of the phenotypic differences.

Implication of Small Vessel Disease MRI Markers in Alzheimer's Disease and Lewy Body Disease

BACKGROUND

Small vessel disease (SVD) magnetic resonance imaging (MRI) markers including deep and periventricular white matter hyperintensities (PWMH), lacunes, and microbleeds are frequently observed in Alzheimer's disease (AD) and Lewy body disease (LBD), but their implication has not been clearly elucidated.

OBJECTIVE

To investigate the implication of SVD MRI markers in cognitively impaired patients with AD and/or LBD.

METHODS

We consecutively recruited 57 patients with pure AD-related cognitive impairment (ADCI), 49 with pure LBD-related cognitive impairment (LBCI), 45 with mixed ADCI/LBCI, and 34 controls. All participants underwent neuropsychological tests, brain MRI, and amyloid positron emission tomography. SVD MRI markers including the severity of deep and PWMH and the number of lacunes and microbleeds were visually rated. The relationships among vascular risk factors, SVD MRI markers, ADCI, LBCI, and cognitive scores were investigated after controlling for appropriate covariates.

RESULTS

LBCI was associated with more severe PWMH, which was conversely associated with an increased risk of LBCI independently of vascular risk factors and ADCI. PWMH was associated with attention and visuospatial dysfunction independently of vascular risk factors, ADCI, and LBCI. Both ADCI and LBCI were associated with more lobar microbleeds, but not with deep microbleeds.

CONCLUSION

Our findings suggest that PWMH could reflect degenerative process related with LBD, and both AD and LBD independently increase lobar microbleeds.

Neuroanatomical norms in the UK Biobank: The impact of allometric scaling, sex, and age

Few neuroimaging studies are sufficiently large to adequately describe population‐wide variations. This study's primary aim was to generate neuroanatomical norms and individual markers that consider age, sex, and brain size, from 629 cerebral measures in the UK Biobank (N = 40,028). The secondary aim was to examine the effects and interactions of sex, age, and brain allometry—the nonlinear scaling relationship between a region and brain size (e.g., total brain volume)—across cerebral measures. Allometry was a common property of brain volumes, thicknesses, and surface areas (83%) and was largely stable across age and sex. Sex differences occurred in 67% of cerebral measures (median |β| = .13): 37% of regions were larger in males and 30% in females. Brain measures (49%) generally decreased with age, although aging effects varied across regions and sexes. While models with an allometric or linear covariate adjustment for brain size yielded similar significant effects, omitting brain allometry influenced reported sex differences in variance. Finally, we contribute to the reproducibility of research on sex differences in the brain by replicating previous studies examining cerebral sex differences. This large‐scale study advances our understanding of age, sex, and brain allometry's impact on brain structure and provides data for future UK Biobank studies to identify the cerebral regions that covary with specific phenotypes, independently of sex, age, and brain size.

Pathobiological Subtypes of Alzheimer Disease

Alzheimer disease (AD), the most common form of dementia, is a heterogenous disorder with various pathobiological subtypes. In addition to the 4 major subtypes based on the distribution of tau pathology and brain atrophy (typical, limbic predominant, hippocampal sparing, and minimal atrophy [MA]), several other clinical variants showing distinct regional patterns of tau burden have been identified: nonamnestic, corticobasal syndromal, primary progressive aphasia, posterior cortical atrophy, behavioral/dysexecutive, and mild dementia variants. Among the subtypes, differences were found in age at onset, sex distribution, cognitive status, disease duration, APOE genotype, and biomarker levels. The patterns of key network destructions parallel the tau and atrophy patterns of the AD subgroups essentially. Interruption of key networks, in particular the default-mode network that is responsible for cognitive decline, is consistent in hetero-genous AD groups. AD pathology is often associated with co-pathologies: cerebrovascular lesions, Lewy pathology, and TDP-43 proteinopathies. These mixed pathologies essentially influence the clinical picture of AD and may accel-erate disease progression. Unraveling the heterogeneity among the AD spectrum entities is important for opening a window to pathogenic mechanisms affecting the brain and enabling precision medicine approaches as a basis for developing preventive and ultimately successful disease-modifying therapies for AD.

The Roles of Nitric Oxide Synthase/Nitric Oxide Pathway in the Pathology of Vascular Dementia and Related Therapeutic Approaches

Vascular dementia (VaD) is the second most common form of dementia worldwide. It is caused by cerebrovascular disease, and patients often show severe impairments of advanced cognitive abilities. Nitric oxide synthase (NOS) and nitric oxide (NO) play vital roles in the pathogenesis of VaD. The functions of NO are determined by its concentration and bioavailability, which are regulated by NOS activity. The activities of different NOS subtypes in the brain are partitioned. Pathologically, endothelial NOS is inactivated, which causes insufficient NO production and aggravates oxidative stress before inducing cerebrovascular endothelial dysfunction, while neuronal NOS is overactive and can produce excessive NO to cause neurotoxicity. Meanwhile, inflammation stimulates the massive expression of inducible NOS, which also produces excessive NO and then induces neuroinflammation. The vicious circle of these kinds of damage having impacts on each other finally leads to VaD. This review summarizes the roles of the NOS/NO pathway in the pathology of VaD and also proposes some potential therapeutic methods that target this pathway in the hope of inspiring novel ideas for VaD therapeutic approaches.

Concomitant neurodegenerative pathologies contribute to the transition from mild cognitive impairment to dementia

INTRODUCTION

The aged brain frequently exhibits multiple pathologies, rather than a single hallmark pathology (pure pathology [PurP]), ranging from low/intermediate levels of additional pathology (LowP) to mixed severe pathology (mixed SevP). We investigated the frequency of PurP, LowP, and mixed SevP, and the impact of additional LowP on cognition.

METHODS

Data came from 670 cases from the Brains for Dementia research program. Cases were categorized into PurP, mixed SevP, or a main disease with additional LowP; 508 cases had a clinical dementia rating.

RESULTS

69.9% of cases had LowP, 22.7% had PurP, and 7.5% had mixed SevP. Additional LowP increased the likelihood of having mild dementia versus mild cognitive impairment (MCI) by almost 20-fold (odds ratio = 19.5).

DISCUSSION

Most aged individuals have multiple brain pathologies. The presence of one additional LowP can significantly worsen cognitive decline, increasing the risk of transitioning from MCI to dementia 20-fold. Multimorbidity should be considered in dementia research and clinical studies.

Alzheimer's Disease Neuropathological Comorbidities are Common in the Younger-Old

BACKGROUND

Clinicopathological studies have demonstrated that Alzheimer's disease dementia (ADD) is often accompanied by clinically undetectable comorbid neurodegenerative and cerebrovascular disease that alter the rate of cognitive decline. Aside from causing increased variability in clinical response, it is possible that the major ADD comorbidities may not respond to ADD-specific molecular therapeutics.

OBJECTIVE

As most reports have focused on comorbidity in the oldest-old, its extent in younger age groups that are more likely to be involved in clinical trials is largely unknown; our objective is to provide this information.

METHODS

We conducted a survey of neuropathological comorbidities in sporadic ADD using data from the US National Alzheimer's Coordinating Center. Subject data was restricted to those with dementia and meeting National Institute on Aging-Alzheimer's Association intermediate or high AD Neuropathological Change levels, excluding those with known autosomal dominant AD-related mutations.

RESULTS

Highly prevalent ADD comorbidities are not restricted to the oldest-old but are common even in early-onset ADD. The percentage of cases with ADD as the sole major neuropathological diagnosis is highest in the under-60 group, where "pure" ADD cases are still in the minority at 44%. After this AD as a sole major pathology in ADD declines to roughly 20%in the 70s and beyond. Lewy body disease is the most common comorbidity at younger ages but actually is less common at later ages, while for most others, their prevalence increases with age.

CONCLUSION

Alzheimer's disease neuropathological comorbidities are highly prevalent even in the younger-old.

Endothelial Mitochondrial Dysfunction in Cerebral Amyloid Angiopathy and Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent form of dementia. Cerebrovascular dysfunction is one of the earliest events in the pathogenesis of AD, as well as in vascular and mixed dementias. Cerebral amyloid angiopathy (CAA), the deposition of amyloid around cerebral vessels, is observed in up to 90% of AD patients and in approximately 50% of elderly individuals over 80 years of age. CAA is a strong contributor to vascular dysfunction in AD. CAA-laden brain vessels are characterized by dysfunctional hemodynamics and leaky blood-brain barrier (BBB), contributing to clearance failure and further accumulation of amyloid-β (Aβ) in the cerebrovasculature and brain parenchyma. Mitochondrial dysfunction is increasingly recognized as an important early initiator of the pathogenesis of AD and CAA. The objective of this review is to discuss the effects of Aβ on cerebral microvascular cell function, focusing on its impact on endothelial mitochondria. After introducing CAA and its etiology and genetic risk factors, we describe the pathological relationship between cerebrovascular amyloidosis and brain microvascular endothelial cell dysfunction, critically analyzing its roles in disease progression, hypoperfusion, and BBB integrity. Then, we focus on discussing the effect of Aβ challenge on endothelial mitochondrial dysfunction pathways, and their contribution to the progression of neurovascular dysfunction in AD and dementia. Finally, we report potential pharmacological and non-pharmacological mitochondria-targeted therapeutic strategies which may help prevent or delay cerebrovascular failure.

Novel PET Biomarkers to Disentangle Molecular Pathways across Age-Related Neurodegenerative Diseases

There is a need to disentangle the etiological puzzle of age-related neurodegenerative diseases, whose clinical phenotypes arise from known, and as yet unknown, pathways that can act distinctly or in concert. Enhanced sub-phenotyping and the identification of in vivo biomarker-driven signature profiles could improve the stratification of patients into clinical trials and, potentially, help to drive the treatment landscape towards the precision medicine paradigm. The rapidly growing field of neuroimaging offers valuable tools to investigate disease pathophysiology and molecular pathways in humans, with the potential to capture the whole disease course starting from preclinical stages. Positron emission tomography (PET) combines the advantages of a versatile imaging technique with the ability to quantify, to nanomolar sensitivity, molecular targets in vivo. This review will discuss current research and available imaging biomarkers evaluating dysregulation of the main molecular pathways across age-related neurodegenerative diseases. The molecular pathways focused on in this review involve mitochondrial dysfunction and energy dysregulation; neuroinflammation; protein misfolding; aggregation and the concepts of pathobiology, synaptic dysfunction, neurotransmitter dysregulation and dysfunction of the glymphatic system. The use of PET imaging to dissect these molecular pathways and the potential to aid sub-phenotyping will be discussed, with a focus on novel PET biomarkers.

The Nucleus Basalis of Meynert and Its Role in Deep Brain Stimulation for Cognitive Disorders: A Historical Perspective

The nucleus basalis of Meynert (nbM) was first described at the end of the 19th century and named after its discoverer, Theodor Meynert. The nbM contains a large population of cholinergic neurons that project their axons to the entire cortical mantle, the olfactory tubercle, and the amygdala. It has been functionally associated with the control of attention and maintenance of arousal, both key functions for appropriate learning and memory formation. This structure is well-conserved across vertebrates, although its degree of organization varies between species. Since early in the investigation of its functional and pathological significance, its degeneration has been linked to various major neuropsychiatric disorders. For instance, Lewy bodies, a hallmark in the diagnosis of Parkinson's disease, were originally described in the nbM. Since then, its involvement in other Lewy body and dementia-related disorders has been recognized. In the context of recent positive outcomes following nbM deep brain stimulation in subjects with dementia-associated disorders, we review the literature from an historical perspective focusing on how the nbM came into focus as a promising therapeutic option for patients with Alzheimer's disease. Moreover, we will discuss what is needed to further develop and widely implement this approach as well as examine novel medical indications for which nbM deep brain stimulation may prove beneficial.

Roles of glutamate receptors in a novel in vitro model of early, comorbid cerebrovascular, and Alzheimer's diseases

Systemic multimorbidity is highly prevalent in the elderly and, remarkably, coexisting neuropathological markers of Alzheimer's (AD) and cerebrovascular (CVD) diseases are found at autopsy in most brains of patients clinically diagnosed as AD. Little is known on neurodegeneration peculiar to comorbidities, especially at early stages when pathogenesis may propagate at subclinical levels. We developed a novel in vitro model of comorbid CVD/AD in organotypic hippocampal cultures, by combining oxygen-glucose deprivation (OGD) and exposure to amyloid-Aβ oligomers (AβOs), both applied at levels subtoxic to neurons when used in isolation. We focused on synaptic proteins and the roles of glutamate receptors, which have been implicated in many basic and clinical approaches to either CVD or AD. Subtoxic insults by OGD and AβOs synergized to reduce levels of synaptophysin (SYP) and PSD-95 without cell death, while effects of antagonists of either metabotropic or ionotropic glutamate receptors were distinct from reports in models of isolated CVD or AD. In particular, modulation of glutamate receptors differentially impacted SYP and PSD-95, and antagonists of a single receptor subtype had distinct effects when either isolated or combined. Our findings highlight the complexity of CVD/AD comorbidity, help understand variable responses to glutamate receptor antagonists in patients diagnosed with AD and may contribute to future development of therapeutics based on investigation of the pattern of progressive comorbidity.

Neuropathological assessment of the Alzheimer spectrum

Alzheimer disease (AD), the most common form of dementia globally, classically defined a clinicopathological entity, is a heterogenous disorder with various pathobiological subtypes, currently referred to as Alzheimer continuum. Its morphological hallmarks are extracellular parenchymal β-amyloid (amyloid plaques) and intraneuronal (tau aggregates forming neurofibrillary tangles) lesions accompanied by synaptic loss and vascular amyloid deposits, that are essential for the pathological diagnosis of AD. In addition to "classical" AD, several subtypes with characteristic regional patterns of tau pathology have been described that show distinct clinical features, differences in age, sex distribution, biomarker levels, and patterns of key network destructions responsible for cognitive decline. AD is a mixed proteinopathy (amyloid and tau), frequently associated with other age-related co-pathologies, such as cerebrovascular lesions, Lewy and TDP-43 pathologies, hippocampal sclerosis, or argyrophilic grain disease. These and other co-pathologies essentially influence the clinical picture of AD and may accelerate disease progression. The purpose of this review is to provide a critical overview of AD pathology, its defining pathological substrates, and the heterogeneity among the Alzheimer spectrum entities that may provide a broader diagnostic coverage of this devastating disorder as a basis for implementing precision medicine approaches and for ultimate development of successful disease-modifying drugs for AD.

Deep cerebral microbleeds are associated with poor cholinesterase inhibitor treatment response in people with Alzheimer disease

OBJECTIVES

Cholinesterase inhibitors (ChEIs) are the most effective treatment for Alzheimer disease (AD), but the response to treatment varies. Vascular lesions are associated with the pathogenesis of AD, and cerebral microbleeds (CMBs) are an indicator of hemorrhagic vascular pathology, which can be detected through susceptibility-weighted magnetic resonance imaging (SWMRI). This study investigated the association between CMBs and ChEI treatment response in patients with AD.

PATIENTS AND METHODS

We reviewed the medical records of 112 Taiwanese people with mild to moderate AD and at least 2 years of ChEI treatment between 2009 and 2016. Their baseline CMBs were quantified using the Microbleed Anatomical Rating Scale on SWMRI. Cognitive function of the patients was assessed using the Mini-Mental State Examination (MMSE) and Cognitive Abilities Screening Instrument (CASI). Student t test and multivariable logistic regression were used to analyze the association between cognitive decline and CMBs.

RESULTS

The mean age of the study population was 76.0 ± 8.0 years. In total, 79 out of 112 patients were women. The presence of deep, but not lobar CMBs at baseline was associated with a significant cognitive decline according to the MMSE and CASI, particularly in long-term memory, attention, orientation, mental manipulation, and verbal fluency. Among deep CMBs, those in the basal ganglia and thalamus were significantly associated with cognitive decline.

CONCLUSIONS

Deep CMBs, particularly those in the basal ganglia and thalamus, but not lobar CMBs, are associated with poor response to ChEI treatment in people with AD. This can serve as a biomarker for predicting ChEI treatment response.

Severe hyposmia distinguishes neuropathologically confirmed dementia with Lewy bodies from Alzheimer's disease dementia

Many subjects with neuropathologically-confirmed dementia with Lewy bodies (DLB) are never diagnosed during life, instead being categorized as Alzheimer's disease dementia (ADD) or unspecified dementia. Unrecognized DLB therefore is a critical impediment to clinical studies and treatment trials of both ADD and DLB. There are studies that suggest that olfactory function tests may be able to distinguish DLB from ADD, but few of these had neuropathological confirmation of diagnosis. We compared University of Pennsylvania Smell Identification Test (UPSIT) results in 257 subjects that went on to autopsy and neuropathological examination. Consensus clinicopathological diagnostic criteria were used to define ADD and DLB, as well as Parkinson's disease with dementia (PDD), with (PDD+AD) or without (PDD-AD) concurrent AD; a group with ADD and Lewy body disease (LBD) not meeting criteria for DLB (ADLB) and a clinically normal control group were also included. The subjects with DLB, PDD+AD and PDD-AD all had lower (one-way ANOVA p < 0.0001, pairwise Bonferroni p < 0.05) first and mean UPSIT scores than the ADD, ADLB or control groups. For DLB subjects with first and mean UPSIT scores less than 20 and 17, respectively, Firth logistic regression analysis, adjusted for age, gender and mean MMSE score, conferred statistically significant odds ratios of 17.5 and 18.0 for the diagnosis, vs ADD. For other group comparisons (PDD+AD and PDD-AD vs ADD) and UPSIT cutoffs of 17, the same analyses resulted in odds ratios ranging from 16.3 to 31.6 (p < 0.0001). To our knowledge, this is the largest study to date comparing olfactory function in subjects with neuropathologically-confirmed LBD and ADD. Olfactory function testing may be a convenient and inexpensive strategy for enriching dementia studies or clinical trials with DLB subjects, or conversely, reducing the inclusion of DLB subjects in ADD studies or trials.

Neuropathological correlates of parkinsonian disorders in a large Dutch autopsy series

The clinical diagnosis in patients with parkinsonian disorders can be challenging, and a definite diagnosis requires neuropathological confirmation. The aim of this study was to examine whether a clinical diagnosis of Parkinson’s disease (PD) and atypical parkinsonian disorders predict the presence of Lewy pathology (LP) and concomitant neuropathological lesions.

We included 293 donors with a history of parkinsonism without dementia at disease onset, collected by the Netherlands Brain Bank (NBB) from 1989 to 2015. We retrospectively categorized donors according the International Parkinson and Movement Disorder Society clinical diagnostic criteria for PD (MDS-PD criteria) as ‘not PD’, ‘probable PD’ or ‘established PD’. We compared the final clinical diagnosis to presence of neuropathological lesions as defined by BrainNet Europe and National Institute on Aging – Alzheimer's Association guidelines.

LP was present in 150 out of 176 donors (85%) with a clinical diagnosis of PD, in 8 out of 101 donors (8%) with atypical parkinsonian disorders and in 4 out of 16 donors (25%) without a definite clinical diagnosis. Independent from age at death, stages of amyloid-β, but not neurofibrillary tau or neuritic plaques, were higher in donors with LP compared to other types of pathology (p = 0.009). The MDS-PD criteria at a certainty level of ‘probable PD’ predicted presence of LP with a diagnostic accuracy of 89.3%. Among donors with LP, ‘established PD’ donors showed similar Braak α-synuclein stages and stages of amyloid-β, neurofibrillary tau and neuritic plaques compared to ‘not PD’ or ‘probable PD’ donors.

In conclusion, both a clinical diagnosis of PD as well as MDS-PD criteria accurately predicted presence of LP in NBB donors. LP was associated with more widespread amyloid-β pathology, suggesting a link between amyloid-β accumulation and LP formation.

Brain injury-induced dysfunction of the blood brain barrier as a risk for dementia

The blood-brain barrier (BBB) is a complex and dynamic physiological interface between brain parenchyma and cerebral vasculature. It is composed of closely interacting cells and signaling molecules that regulate movement of solutes, ions, nutrients, macromolecules, and immune cells into the brain and removal of products of normal and abnormal brain cell metabolism. Dysfunction of multiple components of the BBB occurs in aging, inflammatory diseases, traumatic brain injury (TBI, severe or mild repetitive), and in chronic degenerative dementing disorders for which aging, inflammation, and TBI are considered risk factors. BBB permeability changes after TBI result in leakage of serum proteins, influx of immune cells, perivascular inflammation, as well as impairment of efflux transporter systems and accumulation of aggregation-prone molecules involved in hallmark pathologies of neurodegenerative diseases with dementia. In addition, cerebral vascular dysfunction with persistent alterations in cerebral blood flow and neurovascular coupling contribute to brain ischemia, neuronal degeneration, and synaptic dysfunction. While the idea of TBI as a risk factor for dementia is supported by many shared pathological features, it remains a hypothesis that needs further testing in experimental models and in human studies. The current review focusses on pathological mechanisms shared between TBI and neurodegenerative disorders characterized by accumulation of pathological protein aggregates, such as Alzheimer's disease and chronic traumatic encephalopathy. We discuss critical knowledge gaps in the field that need to be explored to clarify the relationship between TBI and risk for dementia and emphasize the need for longitudinal in vivo studies using imaging and biomarkers of BBB dysfunction in people with single or multiple TBI.

The Whole Picture: From Isolated to Global MRI Measures of Neurovascular and Neurodegenerative Disease

Structural magnetic resonance imaging (MRI) has been used to characterise the appearance of the brain in cerebral small vessel disease (SVD), ischaemic stroke, cognitive impairment, and dementia. SVD is a major cause of stroke and dementia; features of SVD include white matter hyperintensities (WMH) of presumed vascular origin, lacunes of presumed vascular origin, microbleeds, and perivascular spaces. Cognitive impairment and dementia have traditionally been stratified into subtypes of varying origin, e.g., vascular dementia versus dementia of the Alzheimer's type (Alzheimer's disease; AD). Vascular dementia is caused by reduced blood flow in the brain, often as a result of SVD, and AD is thought to have its genesis in the accumulation of tau and amyloid-beta leading to brain atrophy. But after early seminal studies in the 1990s found neurovascular disease features in around 30% of AD patients, it is becoming recognised that so-called "mixed pathologies" (of vascular and neurodegenerative origin) exist in many more patients diagnosed with stroke, only one type of dementia, or cognitive impairment. On the back of these discoveries, attempts have recently been made to quantify the full extent of degenerative and vascular disease in the brain in vivo on MRI. The hope being that these "global" methods may one day lead to better diagnoses of disease and provide more sensitive measurements to detect treatment effects in clinical trials. Indeed, the "Total MRI burden of cerebral small vessel disease", the "Brain Health Index" (BHI), and "MRI measure of degenerative and cerebrovascular pathology in Alzheimer disease" have all been shown to have stronger associations with clinical and cognitive phenotypes than individual brain MRI features. This chapter will review individual structural brain MRI features commonly seen in SVD, stroke, and dementia. The relationship between these features and differing clinical and cognitive phenotypes will be discussed along with developments in their measurement and quantification. The chapter will go on to review emerging methods for quantifying the collective burden of structural brain MRI findings and how these "whole picture" methods may lead to better diagnoses of neurovascular and neurodegenerative disorders.

Links Between Adiponectin and Dementia: From Risk Factors to Pathophysiology

With the aging population, dementia is becoming one of the most serious and troublesome global public health issues. Numerous studies have been seeking for effective strategies to delay or block its progression, but with little success. In recent years, adiponectin (APN) as one of the most abundant and multifunctional adipocytokines related to anti-inflammation, regulating glycogen metabolism and inhibiting insulin resistance (IR) and anti-atherosclerosis, has attracted widespread attention. In this article, we summarize recent studies that have contributed to a better understanding of the extent to which APN influences the risks of developing dementia as well as its pathophysiological progression. In addition, some controversial results interlinked with its effects on cognitive dysfunction diseases will be critically discussed. Ultimately, we aim to gain a novel insight into the pleiotropic effects of APN levels in circulation and suggest potential therapeutic target and future research strategies.

Neurodegenerative diseases as proteinopathies-driven immune disorders

In the pathophysiology of neurodegenerative disorders, the role of misfolded protein deposition leading to neurodegeneration has been primarily discussed. In the last decade, however, it has been proposed a parallel involvement of innate immune activation, chronic inflammation and adaptive immunity in the neurodegeneration mechanisms triggered by proteinopathies. New insights in the neurodegenerative field strongly suggest a role for the immune system in the pathophysiology of neurodegenerative disorders. Therefore, the hypothesis underlining the modulation of the innate and the adaptive immune system in the events linked to brain deposition of misfolded proteins could open new perspectives in the setting of specific immunotherapeutic strategies for the treatment of neurodegenerative diseases. Therefore, we have reviewed the pathogenic hypothesis in neurodegenerative pathologies, underling the links between the deposition of misfolded protein mechanisms and the immune activation.

Comorbid amyloid-β pathology affects clinical and imaging features in VCD

INTRODUCTION

To date, the clinical relevance of comorbid amyloid-β (Aβ) pathology in patients with vascular cognitive disorders (VCD) is largely unknown.

METHODS

We included 218 VCD patients with available cerebrospinal fluid Aβ₄₂ levels. Patients were divided into Aβ+ mild-VCD (n = 84), Aβ- mild-VCD (n = 68), Aβ+ major-VCD (n = 31), and Aβ- major-VCD (n = 35). We measured depression with the Geriatric Depression Scale, cognition with a neuropsychological test battery and derived white matter hyperintensities (WMH) and gray matter atrophy from MRI.

RESULTS

Aβ- patients showed more depressive symptoms than Aβ+. In the major-VCD group, Aβ- patients performed worse on attention (P = .02) and executive functioning (P = .008) than Aβ+. We found no cognitive differences in patients with mild VCD. In the mild-VCD group, Aβ- patients had more WMH than Aβ+ patients, whereas conversely, in the major-VCD group, Aβ+ patients had more WMH. Atrophy patterns did not differ between Aβ+ and Aβ- VCD group.

DISCUSSION

Comorbid Aβ pathology affects the manifestation of VCD, but effects differ by severity of VCD.

Alzheimer's disease medication and outcomes of hospitalisation among patients with dementia

AIMS

The use of Alzheimer disease medication for the treatment of dementia symptoms has shown significant benefits with regards to functional and cognitive outcomes as well as nursing home placement (NHP) and mortality. Hospitalisations in these patient groups are characterised by extended length of stays (LOS), frequent readmissions, frequent NHP and high-mortality rates. The impact of Alzheimer disease medication on the aforementioned outcomes remains still unknown. This study assessed the association of Alzheimer disease medication with outcomes of hospitalisation among patients with Alzheimer disease and other forms of dementia.

METHODS

A dynamic retrospective cohort study from 2004 to 2015 was conducted which claims data from a German health insurance company. People with dementia (PWD) were identified using ICD-10 codes and diagnostic measures. The main predictor of interest was the use of Alzheimer disease medication. Hospitalisation outcomes included LOS, readmissions, NHP and mortality during and after hospitalisation across four hospitalisations. Confounding was addressed using a propensity score throughout all analyses.

RESULTS

A total of 1380 users of Alzheimer disease medication and 6730 non-users were identified. The use of Alzheimer disease medication was associated with significantly shorter LOS during the first hospitalisations with estimates for the second, third and fourth showed a tendency towards shorter hospital stays. In addition, current users of Alzheimer disease medication had a lower risk of hospital readmission after the first two hospitalisations. These associations were not significant for the third and fourth hospitalisations. Post-hospitalisation NHP and mortality rates also tended to be lower among current users than among non-users but differences did not reach statistical significance.

CONCLUSIONS

Our results indicate that Alzheimer disease medication might contribute to a reduction of the LOS and the number of readmissions in PWD.

Effects of Alzheimer's disease and Lewy body disease on subcortical atrophy

BACKGROUND AND PURPOSE

Subcortical structures are affected by neurodegeneration in Alzheimer's disease (AD) and Lewy body disease (LBD). Although the co-occurrence of AD and LBD pathologies and their possible interaction have been reported, the effect of AD and LBD on subcortical structures remains unknown. The effects of AD and LBD on subcortical atrophy and their relationship with cognitive dysfunction were investigated.

METHODS

The cross-sectional study recruited 42 patients with pure AD related cognitive impairment (ADCI), 30 patients with pure LBD related cognitive impairment (LBCI), 58 patients with mixed ADCI and LBCI, and 29 normal subjects. A general linear model was used to compare subcortical volume and shape amongst the groups, to investigate the independent and interaction effects of ADCI and LBCI on subcortical shape and volume, and to analyze the relationship between subcortical volume and cognitive dysfunction in each group.

RESULTS

Alzheimer's disease related cognitive impairment and LBCI were independently associated with subcortical atrophies in the hippocampus and amygdala and in the hippocampus and putamen respectively, but their interaction effect was not significant. Compared to the control group, the pure LBCI group exhibited additional local atrophies in the amygdala, caudate and thalamus. Subcortical atrophies correlated differently with cognitive dysfunction according to the underlying causes of cognitive dysfunction.

CONCLUSIONS

The patterns of subcortical atrophies and their correlation with cognitive dysfunction differ according to the underlying AD, LBD or concomitant AD and LBD.

Limbic-predominant age-related TDP-43 encephalopathy (LATE): consensus working group report

We describe a recently recognized disease entity, limbic-predominant age-related TDP-43 encephalopathy (LATE). LATE neuropathological change (LATE-NC) is defined by a stereotypical TDP-43 proteinopathy in older adults, with or without coexisting hippocampal sclerosis pathology. LATE-NC is a common TDP-43 proteinopathy, associated with an amnestic dementia syndrome that mimicked Alzheimer's-type dementia in retrospective autopsy studies. LATE is distinguished from frontotemporal lobar degeneration with TDP-43 pathology based on its epidemiology (LATE generally affects older subjects), and relatively restricted neuroanatomical distribution of TDP-43 proteinopathy. In community-based autopsy cohorts, ∼25% of brains had sufficient burden of LATE-NC to be associated with discernible cognitive impairment. Many subjects with LATE-NC have comorbid brain pathologies, often including amyloid-β plaques and tauopathy. Given that the 'oldest-old' are at greatest risk for LATE-NC, and subjects of advanced age constitute a rapidly growing demographic group in many countries, LATE has an expanding but under-recognized impact on public health. For these reasons, a working group was convened to develop diagnostic criteria for LATE, aiming both to stimulate research and to promote awareness of this pathway to dementia. We report consensus-based recommendations including guidelines for diagnosis and staging of LATE-NC. For routine autopsy workup of LATE-NC, an anatomically-based preliminary staging scheme is proposed with TDP-43 immunohistochemistry on tissue from three brain areas, reflecting a hierarchical pattern of brain involvement: amygdala, hippocampus, and middle frontal gyrus. LATE-NC appears to affect the medial temporal lobe structures preferentially, but other areas also are impacted. Neuroimaging studies demonstrated that subjects with LATE-NC also had atrophy in the medial temporal lobes, frontal cortex, and other brain regions. Genetic studies have thus far indicated five genes with risk alleles for LATE-NC: GRN, TMEM106B, ABCC9, KCNMB2, and APOE. The discovery of these genetic risk variants indicate that LATE shares pathogenetic mechanisms with both frontotemporal lobar degeneration and Alzheimer's disease, but also suggests disease-specific underlying mechanisms. Large gaps remain in our understanding of LATE. For advances in prevention, diagnosis, and treatment, there is an urgent need for research focused on LATE, including in vitro and animal models. An obstacle to clinical progress is lack of diagnostic tools, such as biofluid or neuroimaging biomarkers, for ante-mortem detection of LATE. Development of a disease biomarker would augment observational studies seeking to further define the risk factors, natural history, and clinical features of LATE, as well as eventual subject recruitment for targeted therapies in clinical trials.

Immediate verbal recall and familial dementia risk: population-based study of over 4000 twins

OBJECTIVE

To investigate the effect of familial risk for dementia on verbal learning by comparing cognitively healthy twins who had demented co-twins with cognitively healthy twins who had cognitively healthy co-twins.

METHODS

4367 twins aged ≥65 years including 1375 twin pairs (533 monozygotic (MZ), 823 dizygotic (DZ) and 19 unknown zygosity pairs) from a population-based Finnish Twin Cohort participated in a cross-sectional telephone assessment for dementia and in a single free recall trial of a 10-item word list.

RESULTS

Cognitively healthy twins with demented co-twins (n=101 pairs) recalled less words than cognitively healthy twins with cognitively healthy co-twins (n=770 pairs) after adjusting for age, sex and education, B=- 0.44, 95%  CI (-0.73 to -0.14), p=0.003. The effect size was similar in MZ (n=31) twins (3.88 vs 4.29 words, B=-0.41, 95%  CI (-0.96 to 0.13)) and DZ (n=66) twins (3.70 vs 4.17 words, B=-0.47, 95%  CI (-0.84 to -0.10)). The heritability estimate of immediate recall (IR) was 0.37, 95%  CI (0.21 to 0.43).

CONCLUSIONS

The results demonstrate that familial risk for dementia is reflected in the IR performance of cognitively healthy older persons. The finding of poorer IR performance in non-affected siblings compared with the general population, together with substantial heritability of IR, supports IR as a useful endophenotype for molecular genetic studies of dementia.