Forecasting the prevalence of preclinical and clinical Alzheimer's disease in the United States

Periodontitis Induced by P. gingivalis-LPS Is Associated With Neuroinflammation and Learning and Memory Impairment in Sprague-Dawley Rats

Background

Periodontitis is one of the most common oral diseases and is a potential risk factor for systemic diseases. In this study, we aimed to investigate the association between periodontitis and learning and memory impairment.

Methods

We established a periodontitis model by topical application of Porphyromonas gingivalis lipopolysaccharide (P. gingivalis-LPS) into the palatal gingival sulcus of the maxillary first molars of 10-week-old male rats for a 10-week period. We assessed alveolar bone resorption using micro-computed tomography analysis and learning and memory ability using the Morris water maze test. We determined the levels of cytokines [interleukin (IL)-1β, IL-6, IL-8, and IL-21] and LPS in the peripheral blood and cortex, as well as toll-like receptor 4 (TLR4)/NF-κB signaling pathway activation, using reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and western blot. We determined activation of microglia and astrocytes, expression of Aβ1-42, APP and Tau by immunohistochemistry. Finally, we measured the expression of amyloid precursor protein (APP) and its key secretases, as well as the Aβ1-40/1-42 ratio, by RT-PCR, western blot, and ELISA.

Results

We found that periodontitis induced learning and memory impairment in the rats. Further, we observed that it induced significant alveolar bone resorption. There was an increase in the levels of inflammatory cytokines and LPS. Moreover, we confirmed TLR4/NF-κB signaling pathway activation. We also observed activated microglia and astrocytes with enlarged cell bodies and irregular protrusions. Finally, we observed the promotion of β- and γ-secretases APP processing.

Conclusion

Our findings indicated that periodontitis was associated with learning and memory impairment, probably induced by neuroinflammation via activating the TLR4/NF-κB signaling pathway. Furthermore, abnormal APP processing could be involved in this progress.

Synaptic Pruning in Alzheimer's Disease: Role of the Complement System

Alz heimer’s disease (AD) continues to threaten aged individuals and health care systems around the world. Human beings have been trying to postpone, reduce, or eliminate the primary risk factor for AD, aging, throughout history. Despite this, there is currently only symptomatic treatment for AD and this treatment is limited to only a handful of FDA approved AD drugs.

An Ethical Discussion on Voluntarily Stopping Eating and Drinking by Proxy Decision Maker or by Advance Directive

The number of people living with Alzheimer disease and other dementias continues to grow because of the aging of the US population. Increasingly, the issue of patient- and/or surrogate-directed withholding of oral, hand-fed food and fluids in cases of late-stage dementia is confronting caregivers. Major media outlets have covered several cases wherein patients with explicit directives or clear surrogate decision making were not allowed to face the end of their lives according to their wishes. Ethical and legal scholars, as well as many end-of-life advocacy groups, are working to develop a framework and provide guidance in these cases. A local hospice organization was faced with these ethical deliberations when an activated proxy decision maker advocated for caregivers to stop hand feeding an incapacitated patient with end-stage dementia. In this article, this case is summarized, and this important ethical issue is presented in the setting of a literature review and nursing implications.

Nerve growth factor in metabolic complications and Alzheimer's disease: Physiology and therapeutic potential

As the population ages, obesity and metabolic complications as well as neurological disorders are becoming more prevalent, with huge economic burdens on both societies and families. New therapeutics are urgently needed. Nerve growth factor (NGF), first discovered in 1950s, is a neurotrophic factor involved in regulating cell proliferation, growth, survival, and apoptosis in both central and peripheral nervous systems. NGF and its precursor, proNGF, bind to TrkA and p75 receptors and initiate protein phosphorylation cascades, resulting in changes of cellular functions, and are associated with obesity, diabetes and its complications, and Alzheimer's disease. In this article, we summarize changes in NGF levels in metabolic and neuronal disorders, the signal transduction initiated by NGF and proNGF, the physiological and pathophysiological relevance, and therapeutic potential in treating chronic metabolic diseases and cognitive decline.

Predicting Functional Dependence in Mild Cognitive Impairment: Differential Contributions of Memory and Executive Functions

BACKGROUND AND OBJECTIVES

Diagnostic criteria for mild cognitive impairment (MCI) exclude functional deficits, yet recent studies suggest that older adults with MCI can exhibit impairment in instrumental activities of daily living (IADL). To assist health care providers in detecting functional vulnerabilities that often precipitate loss of independence, we: (a) compared IADL dependence in MCI to older adults without cognitive impairment and those with dementia, (b) estimated the odds of dependence on specific IADLs in MCI, and (c) investigated the differential contributions of memory and executive functions to IADL dependence.

RESEARCH DESIGN AND METHODS

Participants were older adults (Mage = 77.58 ± 11.05) in Maryland, USA (N = 512) community and postacute rehabilitation settings. Analysis was performed on Brief Cognitive Assessment Tool (BCAT) and the Functional Activities Questionnaire (FAQ) data that assessed participants' cognitive functioning and IADL dependence, respectively.

RESULTS

61.04% of participants with MCI were dependent on one or more IADLs. MCI was associated with significantly greater odds of dependence than normal cognition on 7 of the 10 IADLs (odds ratios = 2.62-4.66). Impairment in memory and executive functions significantly predicted IADL dependence (18.52% of variance beyond demographics); executive functions were the stronger predictor, particularly for complex finances, complex cooking, and remembering events.

DISCUSSION AND IMPLICATIONS

IADL dependence can occur even in MCI. Testing suggestive of MCI should alert clinicians to further investigate the older adult's profile of cognitive and functional limitations to highlight targets for caregiver support and promote independence by "right-sizing" community or facility resources.

Redefining the Care Continuum to Create a Pipeline to Dementia Care for Minority Populations

Multiple studies show that racial and ethnic minorities with low socioeconomic status are diagnosed with Alzheimer’s disease and Alzheimer’s disease–related dementias (AD/ADRD) in more advanced disease stages, receive fewer formal services, and have worse health outcomes. For primary care providers confronting this challenge, community-based organizations can be key partners in supporting earlier identification of AD/ADRD and earlier entry into treatment, especially for minority groups. The New York University Center for the Study of Asian American Health, set out to culturally adapt and translate The Kickstart-Assess-Evaluate-Refer (KAER) framework created by the Gerontological Society of America to support earlier detection of dementia in Asian American communities and assist in this community-clinical coordinated care. We found that CBOs play a vital role in dementia care, and are often the first point of contact for concerns around cognitive impairment in ethnically diverse communities. A major strength of these centers is that they provide culturally appropriate group education that focuses on whole group quality of life, rather than singling out any individual. They also offer holistic family-centered care and staff have a deep understanding of cultural and social issues that affect care, including family dynamics. For primary care providers confronting the challenge of delivering evidence-based dementia care in the context of the busy primary care settings, community-based organizations can be key partners in supporting earlier identification of AD/ADRD and earlier entry into treatment, especially for minority groups.

The MemTrax Test Compared to the Montreal Cognitive Assessment Estimation of Mild Cognitive Impairment

Cognitive impairment is a leading cause of dysfunction in the elderly. When mild cognitive impairment (MCI) occurs in elderly, it is frequently a prodromal condition to dementia. The Montreal Cognitive Assessment (MoCA) is a commonly used tool to screen for MCI. However, this test requires a face-to-face administration and is composed of an assortment of questions whose responses are added together by the rater to provide a score whose precise meaning has been controversial. This study was designed to evaluate the performance of a computerized memory test (MemTrax), which is an adaptation of a continuous recognition task, with respect to the MoCA. Two outcome measures are generated from the MemTrax test: MemTrax_speed and MemTrax_correct. Subjects were administered the MoCA and the MemTrax test. Based on the results of the MoCA, subjects were divided in two groups of cognitive status: normal cognition (n = 45) and MCI (n = 37). Mean MemTrax scores were significantly lower in the MCI than in the normal cognition group. All MemTrax outcome variables were positively associated with the MoCA. Two methods, computing the average MTX score and linear regression were used to estimate the cutoff values of the MemTrax test to detect MCI. These methods showed that for the outcome MemTrax_speed a score below the range of 0.87 – 91 s^-1 is an indication of MCI, and for the outcome MemTrax_correct a score below the range of 85 – 90% is an indication for MCI.

Protocol of Aerobic Exercise and Cognitive Health (REACH): A Pilot Study

A growing body of evidence supports that aerobic exercise can decrease the risk of future cognitive impairment and Alzheimer's disease (AD). There is a pressing need to rigorously determine whether cognitively normal yet at-risk individuals stand to benefit from the protective effects of exercise. The present study will test the feasibility of an aerobic exercise intervention in such a population and inform the design of a larger-scale randomized, controlled trial examining the effect of aerobic exercise on biomarkers of AD in late-middle-aged, at-risk individuals. This was a single-site, 1 : 1 block-randomized, parallel, two-arm trial. Cognitively normal participants aged 45-80 with documentation of familial and genetic AD risk factors were randomly assigned to one of two interventions. The Usual Physical Activity group was provided educational materials about exercise. The Enhanced Physical Activity intervention delivered 26 weeks of individualized and supervised aerobic exercise. Exercise duration and intensity were incrementally increased to 150 min/week and 70-80% of heart rate reserve, respectively. Retention and adherence were measured to assess study feasibility. In addition, pre- and post- intervention differences between the two arms were evaluated for cardiorespiratory fitness, physical activity, brain glucose metabolism, cerebral structure, vascular health, memory, executive function, and mood. Data from randomized controlled trials of exercise training are needed to identify the proper exercise prescription for reducing accumulation of AD biomarkers in cognitively normal individuals. The current trial will contribute to filling that gap while informing the design of large-scale trials.

Sattar MA, Kamel FO, Ramadan WS, Alzahrani YA. Possible combined effect of perindopril and Azilsartan in an experimental model of dementia in rats

Renin-angiotensin system exerted deleterious effects on learning and cognitive functions through different mechanisms. The present study has been designed to evaluate the protective effect of perindopril and azilsartan as monotherapy or in combination on aluminum chloride (AlCl3) induced neurobehavioral and pathological changes in Alzheimeric rats. Male Wistar rats were divided into nine groups (n = 6); negative control, AlCl3 treated, vehicle, AlCl3 and Azilsartan (3.5 mg/kg, 7 mg/kg) co-treated, AlCl3 and perindopril (0.5 mg/kg, 1 mg/kg) co-treated, AlCl3 and (Azilsartan 3.5 mg/kg + perindopril 0.5 mg/kg), and AlCl3 and (Azilsartan 7 mg/kg + perindopril 1 mg/kg), all groups were treated for consecutive 60 days. Then, memory function was evaluated by the Y- maze test. Amyloid Peptide - 42 (Aβ-42), Acetylcholinesterase (AChE), Malondialdehyde (MDA), Tumor necrosis factor (TNF-α) and Nitric Oxide (NO) levels in the hippocampus were assessed with (ELISA) kits. The histopathological studies of the hippocampal dentate gyrus (DG) and Cornu Ammonis-3 (CA3) were also performed. Oral administration of either azilsartan and perindopril alone or in combined for 60 days have shown; improvement of cognitive function, significant reduction in the hippocampal levels of Aβ-42, Acetylcholinesterase, Malondialdehyde (MDA), Tumor necrosis factor (TNF-α) and reserved most of histopathological changes in dentate gyrus (DG) and Cornu Ammonis-3 (CA3) that mediated by Alcl3. Our behavioral, biochemical, and histopathological studies indicate that perindopril and azilsartan have neuroprotective effects on the AD model of rats induced by AlCl3, suggesting that perindopril and azilsartan may be a candidate drugs for the treatment of AD.

Advances in protein misfolding, amyloidosis and its correlation with human diseases

Protein aggregation, their mechanisms and trends in the field of neurodegenerative diseases is still far from completely being decoded. It is mainly attributed to the complexity surrounding the interaction between proteins which includes various regulatory mechanisms involved with the presentation of abnormal conditions. Although most proteins are functional in their soluble form, they have also been reported to convert themselves into insoluble aggregates under certain conditions naturally. Misfolded protein forms aggregates which are mostly unwanted by the cellular system and are mostly involved in various pathophysiologies including Alzheimer's, Type II Diabetes mellitus, Kurus's etc. Challenges lie in understanding the complex mechanism of protein misfolding and its correlation with clinical evidence. It is often understood that due to the slowness of the process and its association with ageing, timely intervention with drugs or preventive measures will play an essential role in lowering the rate of dementia causing diseases and associated ailments in the future. Today approximately more than 35 proteins have been identified capable of forming amyloids under defined conditions, and nearly all of them have been associated with disease outcomes. This review incorporates a major understanding from the history of diseases associated with protein misfolding, to the current state of neurodegenerative diseases globally, highlighting challenges in drug development and current state of research in a comprehensive manner in the field of protein misfolding diseases. There is increasing clinical association of protein misfolding with regards to amyloids compelling us to thread questions solved and further helping us design possible solutions by generating a pathway-based research on which future work in this field could be driven.

Meningeal Immunity and Its Function in Maintenance of the Central Nervous System in Health and Disease

Neuroimmunology, albeit a relatively established discipline, has recently sparked numerous exciting findings on microglia, the resident macrophages of the central nervous system (CNS). This review addresses meningeal immunity, a less-studied aspect of neuroimmune interactions. The meninges, a triple layer of membranes—the pia mater, arachnoid mater, and dura mater—surround the CNS, encompassing the cerebrospinal fluid produced by the choroid plexus epithelium. Unlike the adjacent brain parenchyma, the meninges contain a wide repertoire of immune cells. These constitute meningeal immunity, which is primarily concerned with immune surveillance of the CNS, and—according to recent evidence—also participates in postinjury CNS recovery, chronic neurodegenerative conditions, and even higher brain function. Meningeal immunity has recently come under the spotlight owing to the characterization of meningeal lymphatic vessels draining the CNS. Here, we review the current state of our understanding of meningeal immunity and its effects on healthy and diseased brains.

Feasibility of Using a Wearable Biosensor Device in Patients at Risk for Alzheimer's Disease Dementia

BACKGROUND

Alzheimer's disease (AD) is the most common and most costly chronic neurodegenerative disease globally. AD develops over an extended period prior to cognitive symptoms, leaving a "window of opportunity" for targeted risk-reduction interventions. Further, this pre-dementia phase includes early physiological changes in sleep and autonomic regulation, for which wearable biosensor devices may offer a convenient and cost-effective method to assess AD-risk.

METHODS

Patients with a family history of AD and no or minimal cognitive complaints were recruited from the Alzheimer's Prevention Clinic at Weill Cornell Medicine and New York-Presbyterian. Of the 40 consecutive patients screened, 34 (85%) agreed to wear a wearable biosensor device (WHOOP). One subject (2.5%) lost the device prior to data collection. Of the remaining subjects, 24 were classified as normal cognition and were asymptomatic, 6 were classified as subjective cognitive decline, and 3 were amyloid-positive (one with pre-clinical AD, one with pre-clinical Lewy-Body Dementia, and one with mild cognitive impairment due to AD). Sleep-cycle, autonomic (heart rate variability [HRV]) and activity measures were collected via WHOOP. Blood biomarkers and neuropsychological testing sensitive to cognitive changes in pre-clinical AD were obtained. Participants completed surveys assessing their sleep-patterns, exercise habits, and attitudes towards WHOOP. The goal of this prospective observational study was to determine the feasibility of using a wrist-worn biosensor device in patients at-risk for AD dementia. Unsupervised machine learning was performed to first separate participants into distinct phenotypic groups using the multivariate biometric data. Additional statistical analyses were conducted to examine correlations between individual biometric measures and cognitive performance.

RESULTS

27 (81.8%) participants completed the follow-up surveys. Twenty-four participants (88.9%) were satisfied with WHOOP after six months, and twenty-three (85.2%) wanted to continue wearing WHOOP. K-means clustering separated participants into two groups. Group 1 was older, had lower HRV, and spent more time in slow-wave sleep (SWS) than Group 2. Group 1 performed better on two cognitive tests assessing executive function: Flanker Inhibitory Attention/Control (FIAC) (p=.031), and Dimensional Change Card Sort (DCCS) (p=.061). In Group 1, DCCS was correlated with SWS (ρ=.68, p=0.024) and HRV (ρ=.6, p=0.019). In Group 2, DCCS was correlated with HRV (ρ=.55, p=0.018). There were no significant differences in blood biomarkers between the two groups.

CONCLUSIONS

Wearable biosensor devices may be a feasible tool to assess AD-related physiological changes. Longitudinal collection of sleep and HRV data may potentially be a non-invasive method for monitoring cognitive changes related to pre-clinical AD. Further study is warranted in larger populations.

Prominent amyloid plaque pathology and cerebral amyloid angiopathy in APP V717I (London) carrier - phenotypic variability in autosomal dominant Alzheimer's disease

The discovery of mutations associated with familial forms of Alzheimer's disease (AD), has brought imperative insights into basic mechanisms of disease pathogenesis and progression and has allowed researchers to create animal models that assist in the elucidation of the molecular pathways and development of therapeutic interventions. Position 717 in the amyloid precursor protein (APP) is a hotspot for mutations associated with autosomal dominant AD (ADAD) and the valine to isoleucine amino acid substitution (V717I) at this position was among the first ADAD mutations identified, spearheading the formulation of the amyloid cascade hypothesis of AD pathogenesis. While this mutation is well described in multiple kindreds and has served as the basis for the generation of widely used animal models of disease, neuropathologic data on patients carrying this mutation are scarce. Here we present the detailed clinical and neuropathologic characterization of an APP V717I carrier, which reveals important novel insights into the phenotypic variability of ADAD cases. While age at onset, clinical presentation and widespread parenchymal beta-amyloid (Aβ) deposition are in line with previous reports, our case also shows widespread and severe cerebral amyloid angiopathy (CAA). This patient also presented with TDP-43 pathology in the hippocampus and amygdala, consistent with limbic predominant age-related TDP-43 proteinopathy (LATE). The APOE ε2/ε3 genotype may have been a major driver of the prominent vascular pathology seen in our case. These findings highlight the importance of neuropathologic examinations of genetically determined AD cases and demonstrate striking phenotypic variability in ADAD cases.

2020 Alzheimer's disease facts and figures

This article describes the public health impact of Alzheimer's disease (AD), including incidence and prevalence, mortality and morbidity, use and costs of care, and the overall impact on caregivers and society. The Special Report discusses the future challenges of meeting care demands for the growing number of people living with Alzheimer's dementia in the United States with a particular emphasis on primary care. By mid-century, the number of Americans age 65 and older with Alzheimer's dementia may grow to 13.8 million. This represents a steep increase from the estimated 5.8 million Americans age 65 and older who have Alzheimer's dementia today. Official death certificates recorded 122,019 deaths from AD in 2018, the latest year for which data are available, making Alzheimer's the sixth leading cause of death in the United States and the fifth leading cause of death among Americans age 65 and older. Between 2000 and 2018, deaths resulting from stroke, HIV and heart disease decreased, whereas reported deaths from Alzheimer's increased 146.2%. In 2019, more than 16 million family members and other unpaid caregivers provided an estimated 18.6 billion hours of care to people with Alzheimer's or other dementias. This care is valued at nearly $244 billion, but its costs extend to family caregivers' increased risk for emotional distress and negative mental and physical health outcomes. Average per-person Medicare payments for services to beneficiaries age 65 and older with AD or other dementias are more than three times as great as payments for beneficiaries without these conditions, and Medicaid payments are more than 23 times as great. Total payments in 2020 for health care, long-term care and hospice services for people age 65 and older with dementia are estimated to be $305 billion. As the population of Americans living with Alzheimer's dementia increases, the burden of caring for that population also increases. These challenges are exacerbated by a shortage of dementia care specialists, which places an increasing burden on primary care physicians (PCPs) to provide care for people living with dementia. Many PCPs feel underprepared and inadequately trained to handle dementia care responsibilities effectively. This report includes recommendations for maximizing quality care in the face of the shortage of specialists and training challenges in primary care.

Content of anti-β-amyloid42 oligomers antibodies in multiple batches from different immunoglobulin preparations

Immunoglobulin preparations are one of the promising drugs for Alzheimer's disease (AD). Anti-β-amyloid (Aβ) oligomers antibodies in immunoglobulin preparations are considered to be critical for the therapeutic effect against Alzheimer's disease. However, the antibodies content in immunoglobulin preparations varies greatly. In order to determine which factor contributes to the difference of the antibodies content, the content of anti-Aβ oligomers antibodies in multiple batches of immunoglobulin preparations from two manufacturers were measured by enzyme-linked immunosorbent assay. The results showed that no significant difference was found in the antibodies content among different bathes of normal immunoglobulin preparations prepared by the same process from the same manufacturer, whereas significant difference was found in the antibodies content between normal immunoglobulin preparations prepared by ethanol fractionation and those by chromatography process from the same manufacturer. In addition, significant variation existed in the antibodies content between normal immunoglobulin preparations and specific immunoglobulin preparations that are produced by plasma pool of immunized donors. Based on analysis of these results, the preparation process and raw plasma could be the main contributing factors affecting the content of anti-Aβ oligomers antibodies in immunoglobulin preparations. This finding might help to develop AD-specific immunoglobulin preparation containing higher content of anti-Aβ oligomers antibodies.

Steps Towards Developing Effective Treatments for Neuropsychiatric Disturbances in Alzheimer's Disease: Insights From Preclinical Models, Clinical Data, and Future Directions

Alzheimer's disease (AD) is the most common form of dementia worldwide. It is mostly known for its devastating effect on memory and learning but behavioral alterations commonly known as neuropsychiatric disturbances (NPDs) are also characteristics of the disease. These include apathy, depression-like behavior, and sleep disturbances, and they all contribute to an increased caregiver burden and earlier institutionalization. The interaction between NPDs and AD pathology is not well understood, but the consensus is that they contribute to disease progression and faster decline. Consequently, recognizing and treating NPDs might improve AD pathology and increase the quality of life for both patients and caregivers. In this review article, we examine previous and current literature on apathy, depressive symptoms, and sleep disturbances in AD patients and preclinical AD mechanistic models. We hypothesize that tau accumulation, beta-amyloid (Aβ) aggregation, neuroinflammation, mitochondrial damage, and loss of the locus coeruleus (LC)-norepinephrine (NE) system all collectively impact the development of NPDs and contribute synergistically to AD pathology. Targeting more than one of these processes might provide the most optimal strategy for treating NPDs and AD. The development of such clinical approaches would be preceded by preclinical studies, for which robust and reliable mechanistic models of NPD-like behavior are needed. Thus, developing effective preclinical research models represents an important step towards a better understanding of NPDs in AD.

Contributions by the Brain Renin-Angiotensin System to Memory, Cognition, and Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive neuron losses in memory-associated brain structures that rob patients of their dignity and quality of life. Five drugs have been approved by the FDA to treat AD but none modify or significantly slow disease progression. New therapies are needed to delay the course of this disease with the ultimate goal of preventing neuron losses and preserving memory functioning. In this review we describe the renin-angiotensin II (AngII) system (RAS) with specific regard to its deleterious contributions to hypertension, facilitation of neuroinflammation and oxidative stress, reduced cerebral blood flow, tissue remodeling, and disruption of memory consolidation and retrieval. There is evidence that components of the RAS, AngIV and Ang(1-7), are positioned to counter such damaging influences and these systems are detailed with the goal of drawing attention to their importance as drug development targets. Ang(1-7) binds at the Mas receptor, while AngIV binds at the AT4 receptor subtype, and these receptor numbers are significantly decreased in AD patients, accompanied by declines in brain aminopeptidases A and N, enzymes essential for the synthesis of AngIV. Potent analogs may be useful to counter these changes and facilitate neuronal functioning and reduce apoptosis in memory associated brain structures of AD patients.

Longitudinal study of self-reported hearing loss and subjective cognitive function decline in women

INTRODUCTION

We investigated the relation between self-reported hearing loss and risk of subjective cognitive function (SCF) decline among women.

METHODS

We conducted a longitudinal study of 20,193 women in the Nurses' Health Study aged ≥66 years who reported their hearing status and had no subjective cognitive concerns in 2012. SCF scores were assessed by a 7-item questionnaire in 2012 and 2014. SCF decline was defined as a new report of at least one cognitive concern during follow-up.

RESULTS

Self-reported hearing loss was associated with higher risk of SCF decline. Compared with women with no hearing loss, the multivariable-adjusted odds ratios (95% confidence interval) for incident SCF score ≥1 were 1.35 (1.25, 1.47), 1.39 (1.24, 1.56), and 1.40 (1.21, 1.75) among women with mild, moderate, and severe hearing loss, respectively. Recent progression of hearing loss was associated with even higher risk.

DISCUSSION

Self-reported hearing loss was associated with higher risk of incident subjective cognitive function decline in women.

History of traumatic brain injury interferes with accurate diagnosis of Alzheimer's dementia: a nation-wide case-control study

Traumatic brain injury (TBI) and Alzheimer's disease (AD) bear a complex relationship, potentially increasing risk of one another reciprocally. However, recent evidence suggests post-TBI dementia exists as a distinct neurodegenerative syndrome, confounding AD diagnostic accuracy in clinical settings. This investigation sought to evaluate TBI's impact on the accuracy of clinician-diagnosed AD using gold standard neuropathological criteria. In this preliminary analysis, data were acquired from the National Alzheimer's Coordinating Centre (NACC), which aggregates clinical and neuropathologic information from Alzheimer's disease centres across the United States. Modified National Institute on Aging-Reagan criteria were applied to confirm AD by neuropathology. Among participants with clinician-diagnosed AD, TBI history was associated with misdiagnosis (false positives) (OR = 1.351 [95% CI: 1.091-1.674], p = 0.006). Among participants without clinician-diagnosed AD, TBI history was not associated with false negatives. TBI moderates AD diagnostic accuracy. Possible AD misdiagnosis can mislead patients, influence treatment decisions, and confound research study designs. Further work examining the influence of TBI on dementia diagnosis is warranted.

Genetic Factors of Alzheimer's Disease Modulate How Diet is Associated with Long-Term Cognitive Trajectories: A UK Biobank Study

BACKGROUND

Fluid intelligence (FI) involves abstract problem-solving without prior knowledge. Greater age-related FI decline increases Alzheimer's disease (AD) risk, and recent studies suggest that certain dietary regimens may influence rates of decline. However, it is uncertain how long-term food consumption affects FI among adults with or without familial history of AD (FH) or APOE4 (ɛ4).

OBJECTIVE

Observe how the total diet is associated with long-term cognition among mid- to late-life populations at-risk and not-at-risk for AD.

METHODS

Among 1,787 mid-to-late-aged adult UK Biobank participants, 10-year FI trajectories were modeled and regressed onto the total diet based on self-reported intake of 49 whole foods from a Food Frequency Questionnaire (FFQ).

RESULTS

Daily cheese intake strongly predicted better FIT scores over time (FH-: β= 0.207, p < 0.001; ɛ4-: β= 0.073, p = 0.008; ɛ4+: β= 0.162, p = 0.001). Alcohol of any type daily also appeared beneficial (ɛ4+: β= 0.101, p = 0.022) and red wine was sometimes additionally protective (FH+: β= 0.100, p = 0.014; ɛ4-: β= 0.59, p = 0.039). Consuming lamb weekly was associated with improved outcomes (FH-: β= 0.066, p = 0.008; ɛ4+: β= 0.097, p = 0.044). Among at risk groups, added salt correlated with decreased performance (FH+: β= -0.114, p = 0.004; ɛ4+: β= -0.121, p = 0.009).

CONCLUSION

Modifying meal plans may help minimize cognitive decline. We observed that added salt may put at-risk individuals at greater risk, but did not observe similar interactions among FH- and AD- individuals. Observations further suggest in risk status-dependent manners that adding cheese and red wine to the diet daily, and lamb on a weekly basis, may also improve long-term cognitive outcomes.

APOE4 Status is Related to Differences in Memory-Related Brain Function in Asymptomatic Older Adults with Family History of Alzheimer's Disease: Baseline Analysis of the PREVENT-AD Task Functional MRI Dataset

BACKGROUND

Episodic memory decline is one of the earliest symptoms of late-onset Alzheimer's disease (AD). Older adults with the apolipoprotein E ɛ4 (+APOE4) genetic risk factor for AD may exhibit altered patterns of memory-related brain activity years prior to initial symptom onset.

OBJECTIVE

Here we report the baseline episodic memory task functional MRI results from the PRe-symptomatic EValuation of Experimental or Novel Treatments for Alzheimer's Disease cohort in Montreal, Canada, in which 327 healthy older adults were scanned within 15 years of their parent's conversion to AD.

METHODS

Volunteers were scanned as they encoded and retrieved object-location spatial source associations. The task was designed to discriminate between brain activity related to spatial source recollection and object-only (recognition) memory. We used multivariate partial least squares (PLS) to test the hypothesis that +APOE4 adults with family history of AD would exhibit altered patterns of brain activity in the recollection-related memory network, comprised of medial frontal, parietal, and medial temporal cortices, compared to APOE4 non-carriers (-APOE4). We also examined group differences in the correlation between event-related brain activity and memory performance.

RESULTS

We found group similarities in memory performance and in task-related brain activity in the recollection network, but differences in brain activity-behavior correlations in ventral occipito-temporal, medial temporal, and medial prefrontal cortices during episodic encoding.

CONCLUSION

These findings are consistent with previous literature on the influence of APOE4 on brain activity and provide new perspective on potential gene-based differences in brain-behavior relationships in people with first-degree family history of AD.

Antidiabetic Drugs for the Risk of Alzheimer Disease in Patients With Type 2 DM Using FAERS

Alzheimer disease (AD) may develop after the onset of type 2 diabetes mellitus (T2DM), and the risk of AD may depend on the antidiabetic drug administered. We compared the risk of AD among 66 085 patients (≥ 65 years) with T2DM (1250 having concomitant AD) who had been administered antidiabetic drug monotherapy for T2DM who had voluntarily reported themselves in the Food and Drug Administration Adverse Event Reporting System. The risk of AD from the use of different antidiabetic drug monotherapies compared to that of metformin monotherapy was assessed by logistic regression. Rosiglitazone (adjusted reporting odds ratio [aROR] = 0.11; 95% confidence interval [CI]: 0.07-0.17; P < .001), exenatide (aROR = 0.22; 95% CI: 0.11-0.37; P < .001), liraglutide (aROR = 0.36; 95% CI: 0.19-0.62; P < .001), dulaglutide (aROR = 0.39; 95% CI: 0.17-0.77; P = .014), and sitagliptin (aROR = 0.75; 95% CI: 0.60-0.93; P = .011) were found to have a significantly lower associated risk of AD than that of metformin. Therefore, the administration of glucagon-like peptide 1 receptor agonists and rosiglitazone may reduce the risk of AD in patients with T2DM.

Meningeal Lymphatics: A Review and Future Directions From a Clinical Perspective

The recent discovery of lymphatic vessels in the meningeal layers calls into question the known mechanisms of fluid and macromolecule homeostasis and immunoregulation within the central nervous system. These meningeal lymphatic vessels and their potential role in the pathophysiology of neurological disease have become a rapidly expanding area of research, with the hopes that they may provide a novel therapeutic target in the treatment of many devastating conditions. This article reviews the current state of knowledge surrounding the anatomical structure of the vessels, their functions in fluid and solute transport and immune surveillance, as well as their studied developmental biology, relationship with the novel hypothesized “glymphatic” system, and implications in neurodegenerative disease in animal models. Furthermore, this review summarizes findings from the human studies conducted thus far regarding the presence, anatomy, and drainage patterns of meningeal lymphatic vessels and discusses, from a clinical perspective, advancements in both imaging technologies and interventional methodologies used to access ultrafine peripheral lymphatic vessels.

Alzheimer's Disease - Why We Need Early Diagnosis

Alzheimer's disease is the leading cause of dementia. However, neither Alzheimer's disease nor Alzheimer's dementia are an inevitable consequence of aging. This review provides an overview of the issues involved in a diagnosis of Alzheimer's disease before an individual meets the criteria for Alzheimer's dementia. It examines how Alzheimer's disease diagnosis rates can be improved, the implications of an early diagnosis for the individual, carer and society, and the importance of risk reduction to prevent or delay progression. Although no disease-modifying agents capable of reversing the initial pathological changes are currently available, it may be possible to prevent or delay the development of dementia in a proportion of the population by modifying exposure to common risk factors. In other individuals, diagnosing the disease or risk of disease early is still valuable so that the individual and their carers have time to make choices and plan for the future, and to allow access to treatments that can help manage symptoms. Primary healthcare professionals play a pivotal role in recognising individuals at risk, recommending lifestyle changes in mid-adult life that can prevent or slow down the disease, and in timely diagnosis. Early intervention is the optimal strategy, because the patient's level of function is preserved for longer.

The role of astrocytic glutamate transporters GLT-1 and GLAST in neurological disorders: Potential targets for neurotherapeutics

Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS) which initiates rapid signal transmission in the synapse before its re-uptake into the surrounding glia, specifically astrocytes. The astrocytic glutamate transporters glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) and their human homologs excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2), respectively, are the major transporters which take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with various neurological disorders, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), manganism, ischemia, schizophrenia, epilepsy, and autism. While the mechanisms of neurological disorders are not well understood, the dysregulation of GLAST/GLT-1 may play a significant role in excitotoxicity and associated neuropathogenesis. The expression and function of GLAST/GLT-1 may be dysregulated at the genetic, epigenetic, transcriptional or translational levels, leading to high levels of extracellular glutamate and excitotoxicity. Consequently, understanding the regulatory mechanisms of GLAST/GLT-1 has been an area of interest in developing therapeutics for the treatment of neurological disorders. Pharmacological agents including β-lactam antibiotics, estrogen/selective estrogen receptor modulators (SERMs), growth factors, histone deacetylase inhibitors (HDACi), and translational activators have shown significant efficacy in enhancing the expression and function of GLAST/GLT-1 and glutamate uptake both in vitro and in vivo. This comprehensive review will discuss the regulatory mechanisms of GLAST/GLT-1, their association with neurological disorders, and the pharmacological agents which mediate their expression and function. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

Individualized clinical management of patients at risk for Alzheimer's dementia

INTRODUCTION

Multidomain intervention for Alzheimer's disease (AD) risk reduction is an emerging therapeutic paradigm.

METHODS

Patients were prescribed individually tailored interventions (education/pharmacologic/nonpharmacologic) and rated on compliance. Normal cognition/subjective cognitive decline/preclinical AD was classified as Prevention. Mild cognitive impairment due to AD/mild-AD was classified as Early Treatment. Change from baseline to 18 months on the modified Alzheimer's Prevention Cognitive Composite (primary outcome) was compared against matched historical control cohorts. Cognitive aging composite (CogAging), AD/cardiovascular risk scales, and serum biomarkers were secondary outcomes.

RESULTS

One hundred seventy-four were assigned interventions (age 25-86). Higher-compliance Prevention improved more than both historical cohorts (P = .0012, P < .0001). Lower-compliance Prevention also improved more than both historical cohorts (P = .0088, P < .0055). Higher-compliance Early Treatment improved more than lower compliance (P = .0007). Higher-compliance Early Treatment improved more than historical cohorts (P < .0001, P = .0428). Lower-compliance Early Treatment did not differ (P = .9820, P = .1115). Similar effects occurred for CogAging. AD/cardiovascular risk scales and serum biomarkers improved.

DISCUSSION

Individualized multidomain interventions may improve cognition and reduce AD/cardiovascular risk scores in patients at-risk for AD dementia.

The evolution of geriatric neurology

The founders of neurology in the late 19th century and early 20th century laid the foundation for modern geriatric neurology by detailed observations, in their patients, of the clinical expressions of aging of the nervous system. Further advances in clinical manifestations of aging and more detailed examination of disease states in the elderly accelerated in the last quarter of the 20th century. Basic, translational, and clinical research support of geriatric neurology studies expanded and advanced during this period and into the 21st century. The size and sophistication of this movement was stimulated by a number of factors: the successful development of geriatrics as a specialty in primary care, internal medicine, and psychiatry; the projected growth of the geriatric population; and the projections of the number of people with Alzheimer's disease. However, there were and continue to be inadequate numbers of trained geriatric neurologists available to care for the "silver tsunami" of elderly patients with age-related diseases that will present in the next 3 decades. The combination of massive investment in dementia/Alzheimer's research in the past decade, widespread awareness among researchers and trainees of the opportunities to do research in age-related diseases, and the need for further knowledge of neurodegenerative diseases led to a broad expansion of research efforts. Longitudinal clinical studies of the elderly and the advent of sophisticated neuroimaging, genetics, and laboratory techniques are advancing the field. The initiation of therapeutic interventions has led to cautious optimism about the ability to ameliorate suffering in these patients and diminish the burdens of central nervous system aging.

A Series of New Hydrazone Derivatives: Synthesis, Molecular Docking and Anticholinesterase Activity Studies

BACKGROUND

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are known to be serine hydrolase enzymes responsible for the hydrolysis of acetylcholine (ACh), which is a significant neurotransmitter for regulation of cognition in animals. Inhibition of cholinesterases is an effective method to curb Alzheimer's disease, a progressive and fatal neurological disorder.

OBJECTIVE

In this study, 30 new hydrazone derivatives were synthesized. Then we evaluated their anticholinesterase activity of compounds. We also tried to get insights into binding interactions of the synthesized compounds in the active site of both enzymes by using molecular docking approach.

METHODS

The compounds were synthesized by the reaction of various substituted/nonsubstituted benzaldehydes with 6-(substitute/nonsubstituephenyl)-3(2H)-pyridazinone-2-yl propiyohydrazide. Anticholinesterase activity of the compounds was determined using Ellman's method. Molecular docking studies were done by using the ADT package version 1.5.6rc3 and showed by Maestro. RMSD values were obtained using Lamarckian Genetic Algorithm and scoring function of AutoDock 4.2 release 4.2.5.1 software.

RESULTS

The activities of the compounds were compared with galantamine as cholinesterase enzyme inhibitor, where some of the compounds showed higher BChE inhibitory activity than galantamine. Compound F111 was shown to be the best BChE inhibitor effective in 50 μM dose, providing 89.43% inhibition of BChE (IC50=4.27±0.36 μM).

CONCLUSION

This study supports that novel hydrazone derivates may be used for the development of new BChE inhibitory agents.

Curcumin, Hormesis and the Nervous System

Curcumin is a polyphenol compound extracted from the rhizome of Curcuma longa Linn (family Zingiberaceae) commonly used as a spice to color and flavor food. Several preclinical studies have suggested beneficial roles for curcumin as an adjuvant therapy in free radical-based diseases, mainly neurodegenerative disorders. Indeed, curcumin belongs to the family of hormetins and the enhancement of the cell stress response, mainly the heme oxygenase-1 system, is actually considered the common denominator for this dual response. However, evidence-based medicine has clearly demonstrated the lack of any therapeutic effect of curcumin to contrast the onset or progression of neurodegeneration and related diseases. Finally, the curcumin safety profile imposes a careful analysis of the risk/benefit balance prior to proposing chronic supplementation with curcumin.

Behavioral versus Biological Definitions of Dementia Symptoms: Recognizing that Worthwhile Interventions already Exist

BACKGROUND

The 2018 Alzheimer's Disease Facts and Figures special report includes two new guidelines for measuring dementia symptoms. The first requires that a biomarker (biological factor) be added to a doctor's clinical judgment of the cause of symptoms when determining whether dementia is present. The second involves identifying four stages of dementia: normal cognition, preclinical, MCI and dementia. Now only those with defining brain pathologies and significant symptoms will be judged to be persons with stage 4 dementia. This article examines the implications of adopting these two new guidelines. The implications are in terms of whether worthwhile dementia interventions can be said to exist, and the extent to which symptoms have to change for an intervention to be judged to have reduced the prevalence of dementia.

METHODS

A cost-benefit framework is used to examine the implications of the new guidelines. To undertake a cost-benefit analysis (CBA) a measure of dementia symptoms change is required for any intervention to be judged effective. A behavioral measure of dementia symptoms is thought more useful than a biological one. The instrument that is recommended and explained is the clinical dementia rating (CDR) scale, which is measured on a 0-to-18 interval. Using this instrument, three CBAs can be shown to exist, and from a contracted version of the CDR, estimates of the prevalence rates for the four stages of dementia are derived. The implications for future dementia research of using the full CDR instrument is presented in the discussion section.

RESULTS

The three CBAs that are reported and explained are years of education, Medicare eligibility and hearing aids. For each intervention, the analysis is in terms of demonstrating that it is effective, beneficial and socially worthwhile.

CONCLUSIONS

By using a behavioral rather than a biological definition of dementia symptoms, we can show that worthwhile interventions already exist.

Prevalence of Biologically vs Clinically Defined Alzheimer Spectrum Entities Using the National Institute on Aging-Alzheimer's Association Research Framework

Importance

A National Institute on Aging-Alzheimer's Association (NIA-AA) workgroup recently published a research framework in which Alzheimer disease is defined by neuropathologic or biomarker evidence of β-amyloid plaques and tau tangles and not by clinical symptoms.

Objectives

To estimate the sex- and age-specific prevalence of 3 imaging biomarker-based definitions of the Alzheimer disease spectrum from the NIA-AA research framework and to compare these entities with clinically defined diagnostic entities commonly linked with Alzheimer disease.

Design, Setting, and Participants

The Mayo Clinic Study of Aging (MCSA) is a population-based cohort study of cognitive aging in Olmsted County, Minnesota. The MCSA in-person participants (n = 4660) and passively ascertained (ie, through the medical record rather than in-person) individuals with dementia (n = 553) aged 60 to 89 years were included. Subsets underwent amyloid positron emission tomography (PET) (n = 1524) or both amyloid and tau PET (n = 576). Therefore, this study included 3 nested cohorts examined between November 29, 2004, and June 5, 2018. Data were analyzed between February 19, 2018, and March 26, 2019.

Main Outcomes and Measures

The sex- and age-specific prevalence of the following 3 biologically defined diagnostic entities was estimated: Alzheimer continuum (abnormal amyloid regardless of tau status), Alzheimer pathologic change (abnormal amyloid but normal tau), and Alzheimer disease (abnormal amyloid and tau). These were compared with the prevalence of 3 clinically defined diagnostic groups (mild cognitive impairment or dementia, dementia, and clinically defined probable Alzheimer disease).

Results

The median (interquartile range) age was 77 (72-83) years in the clinical cohort (n = 5213 participants), 77 (70-83) years in the amyloid PET cohort (n = 1524 participants), and 77 (69-83) years in the tau PET cohort (n = 576 participants). There were roughly equal numbers of women and men. The prevalence of all diagnostic entities (biological and clinical) increased rapidly with age, with the exception of Alzheimer pathologic change. The prevalence of biological Alzheimer disease was greater than clinically defined probable Alzheimer disease for women and men. Among women, these values were 10% (95% CI, 6%-14%) vs 1% (95% CI, 1%-1%) at age 70 years and 33% (95% CI, 25%-41%) vs 10% (95% CI, 9%-12%) at age 85 years (P < .001). Among men, these values were 9% (95% CI, 5%-12%) vs 1% (95% CI, 0%-1%) at age 70 years and 31% (95% CI, 24%-38%) vs 9% (95% CI, 8%-11%) at age 85 years (P < .001). The only notable difference by sex was a greater prevalence of the mild cognitive impairment or dementia clinical category among men than women.

Conclusions and Relevance

Results of this study suggest that biologically defined Alzheimer disease is more prevalent than clinically defined probable Alzheimer disease at any age and is 3 times more prevalent at age 85 years among both women and men. This difference is mostly driven by asymptomatic individuals with biological Alzheimer disease. These findings illustrate the magnitude of the consequences on public health that potentially exist by intervening with disease-specific treatments to prevent symptom onset.

The effects of insulin and insulin-like growth factor I on amyloid precursor protein phosphorylation in in vitro and in vivo models of Alzheimer's disease

Alzheimer's disease (AD) is a growing problem worldwide, and there are currently no effective treatments for this devastating disease. The neurotrophic growth factors insulin and insulin-like growth factor-I (IGF-I) are currently being investigated as potential therapeutic approaches for AD in preclinical and clinical studies. However, given that the metabolic syndrome (MetS) and diabetes are risk factors for AD, it is unknown how associated insulin resistance (IR) in the brain may impact the effectiveness of these therapies for AD. In this report, we therefore investigated the mechanisms underlying the effects of insulin and IGF-I on AD-associated pathology in the context of IR, with particular emphasis on phosphorylation of amyloid precursor protein (APP), a key step in promoting amyloid plaque formation in AD. Both insulin and IGF-I decreased APP phosphorylation in cultured primary cortical neurons, supporting their therapeutic use in AD. Induction of IR blocked the beneficial effect of insulin and reduced the effect of IGF-I on APP dephosphorylation. These effects were mediated by the phosphatidylinositol 3-kinase (PI3-K)/protein kinase B (Akt) pathway, as inhibition of this pathway during IR restored the effect of IGF-I on APP dephosphorylation. Finally, we explored the translational relevance of these results in vivo by demonstrating that high fat diet fed mice, a robust model of IR and MetS, exhibited the expected increased brain APP phosphorylation. Overall, these data suggest that the beneficial therapeutic effect of insulin and IGF-I on APP phosphorylation is negatively impacted by IR, and suggest that insulin and IGF-I alone may not be appropriate therapies for AD patients with IR, MetS, or diabetes.

Lymphatic and blood systems: Identical or fraternal twins?

Blood and lymphatic systems work in close collaboration to ensure their respective physiological functions. The lymphatic vessel network is being extensively studied, but has been overlooked as compared to the blood vasculature mainly due to the problematic discrimination of lymphatic vessels from the blood ones. This issue has been fortunately resolved in the past decade leading to the emergence of a huge amount of data in lymphatic biology revealing many shared features with the blood vasculature. However, this likeliness between the two vascular systems may lead to a simplistic view of lymphatics and a direct transcription of what is known for the blood system to the lymphatic one, thereby neglecting the lymphatic specificities. In this context, this review aims to clarify the main differences between the two vascular systems focusing on recently discovered lymphatic features.

Duration of preclinical, prodromal, and dementia stages of Alzheimer's disease in relation to age, sex, and APOE genotype

INTRODUCTION

We estimated the age-specific duration of the preclinical, prodromal, and dementia stages of Alzheimer's disease (AD) and the influence of sex, setting, apolipoprotein E (APOE) genotype, and cerebrospinal fluid tau on disease duration.

METHODS

We performed multistate modeling in a combined sample of 6 cohorts (n = 3268) with death as the end stage and estimated the preclinical, prodromal, and dementia stage duration.

RESULTS

The overall AD duration varied between 24 years (age 60) and 15 years (age 80). For individuals presenting with preclinical AD, age 70, the estimated preclinical AD duration was 10 years, prodromal AD 4 years, and dementia 6 years. Male sex, clinical setting, APOE ε4 allele carriership, and abnormal cerebrospinal fluid tau were associated with a shorter duration, and these effects depended on disease stage.

DISCUSSION

Estimates of AD disease duration become more accurate if age, sex, setting, APOE, and cerebrospinal fluid tau are taken into account. This will be relevant for clinical practice and trial design.

Cognitive and Functional Status of Persons Newly Enrolled at Dementia-Specific Adult Day Centers and Burden of Their Caregivers

Background and Objectives

Recognizing the important role that dementia-specific adult day centers have in maintaining persons with a neurocognitive disorder in their home, this article examines three critical indicators at the time when people first enroll in such a center: cognitive and functional impairment of the enrollee, and burden reported by their family caregivers. We also considered variations in these 3 indicators by race/ethnicity and by the relationship of caregiver to the new enrollee.

Research Design and Methods

We conducted a secondary analysis of data collected by a nonprofit organization operating 11 dementia-specific adult day centers located on the east coast of Florida. Nursing staff conducted intake interviews with enrollees and their caregivers, and assessed functional status within one month of admission. Instruments included the Zarit Burden Scale and components of the Minimum Data Set: the Brief Interview for Mental Status (BIMS) and 4 measures of functional status.

Results

On average the cognitive scores of newly enrollees were well-within the range indicated for severe impairment, and these levels did not differ by race/ethnicity. Burden reported by caregivers however differed significantly, with Latinx caregivers reporting the greatest burden and African American/Black caregivers reporting the least. Further, while daughters generally reported higher levels of burden than other family caregivers, Black daughters reported the least.

Discussion and Implications

Results suggest a need for greater dissemination efforts about adult day programs to the Latinx community, as well as attention to the disparate burden placed upon differing family relationships of caregivers to enrollees.

The BACE-1 inhibitor CNP520 for prevention trials in Alzheimer's disease

The beta‐site amyloid precursor protein cleaving enzyme‐1 (BACE‐1) initiates the generation of amyloid‐β (Aβ), and the amyloid cascade leading to amyloid plaque deposition, neurodegeneration, and dementia in Alzheimer's disease (AD). Clinical failures of anti‐Aβ therapies in dementia stages suggest that treatment has to start in the early, asymptomatic disease states. The BACE‐1 inhibitor CNP520 has a selectivity, pharmacodynamics, and distribution profile suitable for AD prevention studies. CNP520 reduced brain and cerebrospinal fluid (CSF) Aβ in rats and dogs, and Aβ plaque deposition in APP‐transgenic mice. Animal toxicology studies of CNP520 demonstrated sufficient safety margins, with no signs of hair depigmentation, retina degeneration, liver toxicity, or cardiovascular effects. In healthy adults ≥ 60 years old, treatment with CNP520 was safe and well tolerated and resulted in robust and dose‐dependent Aβ reduction in the cerebrospinal fluid. Thus, long‐term, pivotal studies with CNP520 have been initiated in the Generation Program.

NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease

In 2011, the National Institute on Aging and Alzheimer’s Association created separate diagnostic recommendations for the preclinical, mild cognitive impairment, and dementia stages of Alzheimer’s disease. Scientific progress in the interim led to an initiative by the National Institute on Aging and Alzheimer’s Association to update and unify the 2011 guidelines. This unifying update is labeled a “research framework” because its intended use is for observational and interventional research, not routine clinical care. In the National Institute on Aging and Alzheimer’s Association Research Framework, Alzheimer’s disease (AD) is defined by its underlying pathologic processes that can be documented by postmortem examination or in vivo by biomarkers. The diagnosis is not based on the clinical consequences of the disease (i.e., symptoms/signs) in this research framework, which shifts the definition of AD in living people from a syndromal to a biological construct. The research framework focuses on the diagnosis of AD with biomarkers in living persons. Biomarkers are grouped into those of β amyloid deposition, pathologic tau, and neurodegeneration [AT(N)]. This ATN classification system groups different biomarkers (imaging and biofluids) by the pathologic process each measures. The AT(N) system is flexible in that new biomarkers can be added to the three existing AT(N) groups, and new biomarker groups beyond AT(N) can be added when they become available. We focus on AD as a continuum, and cognitive staging may be accomplished using continuous measures. However, we also outline two different categorical cognitive schemes for staging the severity of cognitive impairment: a scheme using three traditional syndromal categories and a six-stage numeric scheme. It is important to stress that this framework seeks to create a common language with which investigators can generate and test hypotheses about the interactions among different pathologic processes (denoted by biomarkers) and cognitive symptoms. We appreciate the concern that this biomarker-based research framework has the potential to be misused. Therefore, we emphasize, first, it is premature and inappropriate to use this research framework in general medical practice. Second, this research framework should not be used to restrict alternative approaches to hypothesis testing that do not use biomarkers. There will be situations where biomarkers are not available or requiring them would be counterproductive to the specific research goals (discussed in more detail later in the document). Thus, biomarker-based research should not be considered a template for all research into age-related cognitive impairment and dementia; rather, it should be applied when it is fit for the purpose of the specific research goals of a study. Importantly, this framework should be examined in diverse populations. Although it is possible that β-amyloid plaques and neurofibrillary tau deposits are not causal in AD pathogenesis, it is these abnormal protein deposits that define AD as a unique neurodegenerative disease among different disorders that can lead to dementia. We envision that defining AD as a biological construct will enable a more accurate characterization and understanding of the sequence of events that lead to cognitive impairment that is associated with AD, as well as the multifactorial etiology of dementia. This approach also will enable a more precise approach to interventional trials where specific pathways can be targeted in the disease process and in the appropriate people.

Enhancing face validity of mouse models of Alzheimer's disease with natural genetic variation

Classical laboratory strains show limited genetic diversity and do not harness natural genetic variation. Mouse models relevant to Alzheimer's disease (AD) have largely been developed using these classical laboratory strains, such as C57BL/6J (B6), and this has likely contributed to the failure of translation of findings from mice to the clinic. Therefore, here we test the potential for natural genetic variation to enhance the translatability of AD mouse models. Two widely used AD-relevant transgenes, APPswe and PS1de9 (APP/PS1), were backcrossed from B6 to three wild-derived strains CAST/EiJ, WSB/EiJ, PWK/PhJ, representative of three Mus musculus subspecies. These new AD strains were characterized using metabolic, functional, neuropathological and transcriptional assays. Strain-, sex- and genotype-specific differences were observed in cognitive ability, neurodegeneration, plaque load, cerebrovascular health and cerebral amyloid angiopathy. Analyses of brain transcriptional data showed strain was the greatest driver of variation. We identified significant variation in myeloid cell numbers in wild type mice of different strains as well as significant differences in plaque-associated myeloid responses in APP/PS1 mice between the strains. Collectively, these data support the use of wild-derived strains to better model the complexity of human AD.

Multistate models and lifetime risk estimation: Application to Alzheimer's disease

The lifetime risk of a clinical condition is the probability of onset of the condition during one's lifespan. Recent advances in Alzheimer's disease (AD) research have identified screening tests for biomarkers that can identify persons who are in the earliest stages of the AD process but who do not yet have any clinical signs or symptoms. A critical question asked by patients and clinicians is, what is the probability an individual will develop AD dementia during his or her lifetime? Here, we discuss estimation of lifetime risks using biomarkers for preclinical disease based on a discrete nonhomogeneous Markov multistate model for the disease process. We allow the transition probabilities to depend on chronological age. In addition, we allow the probabilities to depend on calendar time to account for possible calendar trends in death rates and to evaluate the impact on lifetime risks of future interventions designed to slow disease progression. We develop estimating equations for calculating the lifetime risks from the nonhomogeneous multistate Markov model. Estimates of lifetime risks for AD dementia based on biomarkers for preclinical disease are presented.

A brief history of "Alzheimer disease": Multiple meanings separated by a common name

The field of Alzheimer disease (AD) has a nosologic problem: The diagnostic label "Alzheimer disease" has several distinctive meanings. The term probable AD was introduced in 1984 to designate a clinically diagnosed acquired and progressive amnestic dementia for which there was no evidence for another etiology. Probable AD represented a clinicopathologic entity that assumed a specific and sensitive linkage between amnestic dementia and the neuropathology of β-amyloid-containing neuritic plaques and tau-containing neurofibrillary tangles. The clinicopathologic model represented by probable AD was adapted in abbreviated form for population-based studies and general clinical practice, although the uncertainty connoted by "probable" was often overlooked. Representing the growing public awareness of later life cognitive impairment, a vernacular meaning of AD arose out of the clinicopathologic model in which AD represented all dementia not due to another clinically apparent cause. In contrast, by the 1990s, neuropathologists settled on a definition of AD based entirely on a sufficient burden of neuritic plaques and neurofibrillary tangles at postmortem examination, regardless of antemortem clinical status. In the last decade, the availability of fluid and imaging biomarkers that measure β-amyloid and tau abnormalities has enabled antemortem pathobiological diagnoses, highlighting the divide between the clinicopathologic model, the vernacular usage, and the pathobiological models. Each definition has value. However, the meanings of AD as defined by each of these models are not interchangeable. The pathobiological one is the only one that is unambiguous.

Data-Driven Analysis of Age, Sex, and Tissue Effects on Gene Expression Variability in Alzheimer's Disease

Alzheimer's disease (AD) has been categorized by the Centers for Disease Control and Prevention (CDC) as the 6^th leading cause of death in the United States. AD is a significant health-care burden because of its increased occurrence (specifically in the elderly population), and the lack of effective treatments and preventive methods. With an increase in life expectancy, the CDC expects AD cases to rise to 15 million by 2060. Aging has been previously associated with susceptibility to AD, and there are ongoing efforts to effectively differentiate between normal and AD age-related brain degeneration and memory loss. AD targets neuronal function and can cause neuronal loss due to the buildup of amyloid-beta plaques and intracellular neurofibrillary tangles. Our study aims to identify temporal changes within gene expression profiles of healthy controls and AD subjects. We conducted a meta-analysis using publicly available microarray expression data from AD and healthy cohorts. For our meta-analysis, we selected datasets that reported donor age and gender, and used Affymetrix and Illumina microarray platforms (8 datasets, 2,088 samples). Raw microarray expression data were re-analyzed, and normalized across arrays. We then performed an analysis of variance, using a linear model that incorporated age, tissue type, sex, and disease state as effects, as well as study to account for batch effects, and included binary interactions between factors. Our results identified 3,735 statistically significant (Bonferroni adjusted p < 0.05) gene expression differences between AD and healthy controls, which we filtered for biological effect (10% two-tailed quantiles of mean differences between groups) to obtain 352 genes. Interesting pathways identified as enriched comprised of neurodegenerative diseases pathways (including AD), and also mitochondrial translation and dysfunction, synaptic vesicle cycle and GABAergic synapse, and gene ontology terms enrichment in neuronal system, transmission across chemical synapses and mitochondrial translation. Overall our approach allowed us to effectively combine multiple available microarray datasets and identify gene expression differences between AD and healthy individuals including full age and tissue type considerations. Our findings provide potential gene and pathway associations that can be targeted to improve AD diagnostics and potentially treatment or prevention.