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Neurotherapeutics : the Journal of the... Jan 2022As the prevalence of dementia and Alzheimer's disease (AD) increases worldwide, it is imperative to reflect on the major clinical trials in the prevention of dementia... (Review)
Review
As the prevalence of dementia and Alzheimer's disease (AD) increases worldwide, it is imperative to reflect on the major clinical trials in the prevention of dementia and the challenges that surround them. The pharmaceutical industry has focused on developing drugs that primarily affect the Aβ cascade and tau proteinopathy, while academics have focused on repurposed therapeutics and multi-domain interventions for prevention studies. This paper highlights significant primary, secondary, and tertiary prevention trials for dementia and AD, overall design, methods, and systematic issues to better understand the current landscape of prevention trials. We included 32 pharmacologic intervention trials and 9 multi-domain trials. Fourteen could be considered primary prevention, and 18 secondary or tertiary prevention trials. Major categories were Aβ vaccines, Aβ antibodies, tau antibodies, anti-inflammatories, sex hormones, and Ginkgo biloba extract. The 9 multi-domain studies mainly focused on lifestyle modifications such as blood pressure management, socialization, and physical activity. The lack of validated drug targets, and the complexity of the diagnostic frameworks, eligibility criteria, and outcome measurements for trials, make it difficult to show efficacy for both pharmacological and multi-domain interventions. We hope that this summative analysis of trials will stimulate discussion for scientists and clinicians interested in reviewing and developing preventative interventions for AD.
Topics: Alzheimer Disease; Anti-Inflammatory Agents; Exercise; Humans; Life Style; Research Design
PubMed: 35587314
DOI: 10.1007/s13311-022-01236-5 -
Nature Reviews. Neurology Mar 2011The global prevalence of dementia is estimated to be as high as 24 million, and is predicted to double every 20 years through to 2040, leading to a costly burden of... (Review)
Review
The global prevalence of dementia is estimated to be as high as 24 million, and is predicted to double every 20 years through to 2040, leading to a costly burden of disease. Alzheimer disease (AD) is the leading cause of dementia and is characterized by a progressive decline in cognitive function, which typically begins with deterioration in memory. Before death, individuals with this disorder have usually become dependent on caregivers. The neuropathological hallmarks of the AD brain are diffuse and neuritic extracellular amyloid plaques-which are frequently surrounded by dystrophic neurites-and intracellular neurofibrillary tangles. These hallmark pathologies are often accompanied by the presence of reactive microgliosis and the loss of neurons, white matter and synapses. The etiological mechanisms underlying the neuropathological changes in AD remain unclear, but are probably affected by both environmental and genetic factors. Here, we provide an overview of the criteria used in the diagnosis of AD, highlighting how this disease is related to, but distinct from, normal aging. We also summarize current information relating to AD prevalence, incidence and risk factors, and review the biomarkers that may be used for risk assessment and in diagnosis.
Topics: Alzheimer Disease; Biomarkers; Comorbidity; Global Health; Humans; Hypertension; Prevalence; Radiography; Risk Factors
PubMed: 21304480
DOI: 10.1038/nrneurol.2011.2 -
Handbook of Clinical Neurology 2018Senile plaques and neurofibrillary tangles are the principal histopathologic hallmarks of Alzheimer disease. The essential constituents of these lesions are structurally... (Review)
Review
Senile plaques and neurofibrillary tangles are the principal histopathologic hallmarks of Alzheimer disease. The essential constituents of these lesions are structurally abnormal variants of normally generated proteins: Aβ protein in plaques and tau protein in tangles. At the molecular level, both proteins in a pathogenic state share key properties with classic prions, i.e., they consist of alternatively folded, β-sheet-rich forms of the proteins that autopropagate by the seeded corruption and self-assembly of like proteins. Other similarities with prions include the ability to manifest as polymorphic and polyfunctional strains, resistance to chemical and enzymatic destruction, and the ability to spread within the brain and from the periphery to the brain. In Alzheimer disease, current evidence indicates that the pathogenic cascade follows from the endogenous, sequential corruption of Aβ and then tau. Therapeutic options include reducing the production or multimerization of the proteins, uncoupling the Aβ-tauopathy connection, or promoting the inactivation or removal of anomalous assemblies from the brain. Although aberrant Aβ appears to be the prime mover of Alzheimer disease pathogenesis, once set in motion by Aβ, the prion-like propagation of tauopathy may proceed independently of Aβ; if so, Aβ might be solely targeted as an early preventive measure, but optimal treatment of Alzheimer disease at later stages of the cascade could require intervention in both pathways.
Topics: Alzheimer Disease; Amyloid beta-Peptides; Brain; Diagnosis, Differential; Humans; Prions
PubMed: 29887142
DOI: 10.1016/B978-0-444-63945-5.00016-7 -
Psychogeriatrics : the Official Journal... Jun 2009There are two types of dementia with early onset: (i) presenile dementias; and (ii) senile dementias with early onset. Most patients who develop dementia before 65 years... (Review)
Review
There are two types of dementia with early onset: (i) presenile dementias; and (ii) senile dementias with early onset. Most patients who develop dementia before 65 years of age have Alzheimer's disease (AD). The remainder are likely to have vascular dementia (VaD), frontotemporal dementia, head injury, alcohol intoxication, or metabolic disorder. Presenile dementias, caused by frontotemporal lobar degeneration, progressive supranuclear palsy, and corticobasal degeneration, usually occur in patients of presenile and are rarely seen in patients of senile age. Although the factors responsible for the accelerated onset of the illness are not fully known, genetic abnormalities appear to be important in some types of presenile dementia, such as frontotemporal dementia with parkinsonism linked to chromosome 17. Conversely, senile dementias such as sporadic AD and VaD commonly occur in patients of senile age. These disorders may also occur in patients of presenile age, although less frequently. Alzheimer's disease was originally classified as a 'presenile dementia'. Since the 1980s, 'senile dementia of Alzheimer type' (SDAT) and 'Alzheimer's disease' have been considered to belong to the same pathological entity and both are now known as 'dementia of Alzheimer's type (DAT)' or merely 'Alzheimer's disease'. Rapid progression of cognitive impairment with neuropsychological syndromes and neurological symptoms has been considered a characteristic of early onset AD. However, recently, neurological symptoms such as spastic paraparesis, seizures, and myoclonic convulsions have been reported to occur infrequently in early onset AD, although language problems and visuospatial dysfunctions are common. There are at least three dominant genes that have been identified in cases of familial Alzheimer's disease with early onset, namely the amyloid precursor gene (APP), and the genes encoding presenilin 1 (PSEN1) and presenilin 2 (PSEN2). Therefore, genetic abnormalities are important factors contributing to the earlier onset of the illness. It is also important to investigate the pathophysiological mechanism in relation to genetic abnormalities, environmental factors, physical illnesses, and metabolic disturbances to understand the processes underlying the development of dementia with early onset.
Topics: Age of Onset; Alzheimer Disease; Dementia; Dementia, Vascular; Disease Progression; Humans; Middle Aged; Neurodegenerative Diseases
PubMed: 19604328
DOI: 10.1111/j.1479-8301.2009.00274.x -
Trends in Molecular Medicine Jun 2017Like many humans, non-human primates deposit copious misfolded Aβ protein in the brain as they age. Nevertheless, the complete behavioral and pathologic phenotype of... (Review)
Review
Like many humans, non-human primates deposit copious misfolded Aβ protein in the brain as they age. Nevertheless, the complete behavioral and pathologic phenotype of Alzheimer's disease, including Aβ plaques, neurofibrillary (tau) tangles, and dementia, has not yet been identified in a non-human species. Recent research suggests that the crucial link between Aβ aggregation and tauopathy is somehow disengaged in aged monkeys. Understanding why Alzheimer's disease fails to develop in species that are biologically proximal to humans could disclose new therapeutic targets in the chain of events leading to neurodegeneration and dementia.
Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Humans; Species Specificity
PubMed: 28483344
DOI: 10.1016/j.molmed.2017.04.001 -
Cold Spring Harbor Perspectives in... Apr 2012Neuropsychological assessment has featured prominently over the past 30 years in the characterization of dementia associated with Alzheimer disease (AD). Clinical... (Review)
Review
Neuropsychological assessment has featured prominently over the past 30 years in the characterization of dementia associated with Alzheimer disease (AD). Clinical neuropsychological methods have identified the earliest, most definitive cognitive and behavioral symptoms of illness, contributing to the identification, staging, and tracking of disease. With increasing public awareness of dementia, disease detection has moved to earlier stages of illness, at a time when deficits are both behaviorally and pathologically selective. For reasons that are not well understood, early AD pathology frequently targets large-scale neuroanatomical networks for episodic memory before other networks that subserve language, attention, executive functions, and visuospatial abilities. This chapter reviews the pathognomonic neuropsychological features of AD dementia and how these differ from "normal," age-related cognitive decline and from other neurodegenerative diseases that cause dementia, including cortical Lewy body disease, frontotemporal lobar degeneration, and cerebrovascular disease.
Topics: Age Factors; Alzheimer Disease; Attention; Brain; Dementia; Diagnosis, Differential; Executive Function; Humans; Language; Memory; Neuropsychological Tests
PubMed: 22474609
DOI: 10.1101/cshperspect.a006171 -
The Journal of Clinical Psychiatry Aug 2022Diagnosing early-stage Alzheimer disease can lead to prompt initiation of treatment and slow down symptom progression. However, clinicians are not providing a diagnosis...
Diagnosing early-stage Alzheimer disease can lead to prompt initiation of treatment and slow down symptom progression. However, clinicians are not providing a diagnosis to over half of individuals who meet criteria for dementia. Tests for biomarkers, new symptomatic treatments and disease-modifying agents, and the addition of the preclinical stage to the diagnostic criteria for AD can aid in earlier disease recognition and developing treatment plans. Communicating diagnosis and information on next steps with patients and caregivers can lead to patient and caregiver involvement in decision-making and planning as well as participation in clinical trials and maximizing benefits and lifestyle interventions.
Topics: Alzheimer Disease; Caregivers; Humans
PubMed: 35921505
DOI: 10.4088/JCP.LI21019DH1C -
Current Neuropharmacology 2017Inflammation is a part of the first line of defense of the body against invasive pathogens, and plays a crucial role in tissue regeneration and repair. A proper... (Review)
Review
BACKGROUND
Inflammation is a part of the first line of defense of the body against invasive pathogens, and plays a crucial role in tissue regeneration and repair. A proper inflammatory response ensures the suitable resolution of inflammation and elimination of harmful stimuli, but when the inflammatory reactions are inappropriate it can lead to damage of the surrounding normal cells. The relationship between infections and Alzheimer's Disease (AD) etiology, especially lateonset AD (LOAD) has been continuously debated over the past three decades.
METHODS
This review discusses whether infections could be a causative factor that promotes the progression of AD and summarizes recent investigations associating infectious agents and chronic inflammation with AD. Preventive and therapeutic approaches to AD in the context of an infectious etiology of the disease are also discussed.
RESULTS
Emerging evidence supports the hypothesis of the role of neurotropic viruses from the Herpesviridae family, especially Human herpesvirus 1 (HHV-1), Cytomegalovirus (CMV), and Human herpesvirus 2 (HHV-2), in AD neuropathology. Recent investigations also indicate the association between Hepatitis C virus (HCV) infection and dementia. Among bacteria special attention is focused on spirochetes family and on periodontal pathogens such as Porphyromonas gingivalis or Treponema denticola that could cause chronic periodontitis and possibly contribute to the clinical onset of AD.
CONCLUSION
Chronic viral, bacterial and fungal infections might be causative factors for the inflammatory pathway in AD.
Topics: Alzheimer Disease; Animals; Communicable Diseases; Humans; Inflammation
PubMed: 28294067
DOI: 10.2174/1570159X15666170313122937 -
Progress in Neurobiology Apr 2017None of the proposed mechanisms of Alzheimer's disease (AD) fully explains the distribution patterns of the neuropathological changes at the cellular and regional... (Review)
Review
None of the proposed mechanisms of Alzheimer's disease (AD) fully explains the distribution patterns of the neuropathological changes at the cellular and regional levels, and their clinical correlates. One aspect of this problem lies in the complex genetic, epigenetic, and environmental landscape of AD: early-onset AD is often familial with autosomal dominant inheritance, while the vast majority of AD cases are late-onset, with the ε4 variant of the gene encoding apolipoprotein E (APOE) known to confer a 5-20 fold increased risk with partial penetrance. Mechanisms by which genetic variants and environmental factors influence the development of AD pathological changes, especially neurofibrillary degeneration, are not yet known. Here we review current knowledge of the involvement of the monoaminergic systems in AD. The changes in the serotonergic, noradrenergic, dopaminergic, histaminergic, and melatonergic systems in AD are briefly described. We also summarize the possibilities for monoamine-based treatment in AD. Besides neuropathologic AD criteria that include the noradrenergic locus coeruleus (LC), special emphasis is given to the serotonergic dorsal raphe nucleus (DRN). Both of these brainstem nuclei are among the first to be affected by tau protein abnormalities in the course of sporadic AD, causing behavioral and cognitive symptoms of variable severity. The possibility that most of the tangle-bearing neurons of the LC and DRN may release amyloid β as well as soluble monomeric or oligomeric tau protein trans-synaptically by their diffuse projections to the cerebral cortex emphasizes their selective vulnerability and warrants further investigations of the monoaminergic systems in AD.
Topics: Alzheimer Disease; Animals; Biogenic Monoamines; Humans; Neuropathology; Phosphorylation; tau Proteins
PubMed: 27084356
DOI: 10.1016/j.pneurobio.2016.04.001 -
Mayo Clinic Proceedings Jun 2017Alzheimer disease (AD) was originally conceived as a rare disease that caused presenile dementia but has come to be understood as the most prevalent cause of dementia at... (Review)
Review
Alzheimer disease (AD) was originally conceived as a rare disease that caused presenile dementia but has come to be understood as the most prevalent cause of dementia at any age worldwide. It has an extended preclinical phase characterized by sequential changes in imaging and cerebrospinal fluid biomarkers with subtle memory decline beginning more than a decade before the emergence of symptomatic memory loss heralding the beginning of the mild cognitive impairment stage. The apolipoprotein E ε4 allele is a prevalent and potent risk factor for AD that has facilitated research into its preclinical phase. Cerebral Aβ levels build from preclinical through early dementia stages followed by hyperphosphorylated tau-related pathology, the latter driving cognitive deficits and dementia severity. Structural and molecular imaging can now recapitulate the neuropathology of AD antemortem. Autosomal dominant forms of early-onset familial AD gave rise to the amyloid hypothesis of AD, which, in turn, has led to therapeutic trials of immunotherapy designed to clear cerebral amyloid, but to date results have been disappointing. Genome-wide association studies have identified multiple additional risk factors, but to date none have yielded an effective alternate therapeutic target. Current and future trials aimed at presymptomatic individuals either harboring cerebral amyloid or at genetically high risk offer the hope that earlier intervention might yet succeed where trials in patients with established dementia have failed. A major looming challenge will be that of expensive, incompletely effective disease-modifying therapy: who and when to treat, and how to pay for it.
Topics: Aging; Alzheimer Disease; Apolipoproteins E; Brain; Humans; Magnetic Resonance Imaging
PubMed: 28578785
DOI: 10.1016/j.mayocp.2017.02.011