Showing papers in "Alzheimers & Dementia in 2018"

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

Abstract: 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.

CSF biomarkers of Alzheimer's disease concord with amyloid-β PET and predict clinical progression: A study of fully automated immunoassays in BioFINDER and ADNI cohorts

Abstract: Introduction We studied whether fully automated Elecsys cerebrospinal fluid (CSF) immunoassay results were concordant with positron emission tomography (PET) and predicted clinical progression, even with cutoffs established in an independent cohort. Methods Cutoffs for Elecsys amyloid-β1–42 (Aβ), total tau/Aβ(1–42), and phosphorylated tau/Aβ(1–42) were defined against [18F]flutemetamol PET in Swedish BioFINDER (n = 277) and validated against [18F]florbetapir PET in Alzheimer's Disease Neuroimaging Initiative (n = 646). Clinical progression in patients with mild cognitive impairment (n = 619) was studied. Results CSF total tau/Aβ(1–42) and phosphorylated tau/Aβ(1–42) ratios were highly concordant with PET classification in BioFINDER (overall percent agreement: 90%; area under the curve: 94%). The CSF biomarker statuses established by predefined cutoffs were highly concordant with PET classification in Alzheimer's Disease Neuroimaging Initiative (overall percent agreement: 89%–90%; area under the curves: 96%) and predicted greater 2-year clinical decline in patients with mild cognitive impairment. Strikingly, tau/Aβ ratios were as accurate as semiquantitative PET image assessment in predicting visual read–based outcomes. Discussion Elecsys CSF biomarker assays may provide reliable alternatives to PET in Alzheimer's disease diagnosis.

Understanding the impact of sex and gender in Alzheimer's disease: A call to action

Abstract: Introduction Precision medicine methodologies and approaches have advanced our understanding of the clinical presentation, development, progression, and management of Alzheimer's disease (AD) dementia. However, sex and gender have not yet been adequately integrated into many of these approaches. Methods The Society for Women's Health Research Interdisciplinary Network on AD, comprised of an expert panel of scientists and clinicians, reviewed ongoing and published research related to sex and gender differences in AD. Results The current review is a result of this Network's efforts and aims to: (1) highlight the current state-of-the-science in the AD field on sex and gender differences; (2) address knowledge gaps in assessing sex and gender differences; and (3) discuss 12 priority areas that merit further research. Discussion The exclusion of sex and gender has impeded faster advancement in the detection, treatment, and care of AD across the clinical spectrum. Greater attention to these differences will improve outcomes for both sexes.

Plasma phospho-tau181 increases with Alzheimer's disease clinical severity and is associated with tau- and amyloid-positron emission tomography.

Abstract: Introduction We examined and compared plasma phospho-tau181 (pTau181) and total tau: (1) across the Alzheimer's disease (AD) clinical spectrum; (2) in relation to brain amyloid β (Aβ) positron emission tomography (PET), tau PET, and cortical thickness; and (3) as a screening tool for elevated brain Aβ. Methods Participants included 172 cognitively unimpaired, 57 mild cognitively impaired, and 40 AD dementia patients with concurrent Aβ PET (Pittsburgh compound B), tau PET (AV1451), magnetic resonance imaging, plasma total tau, and pTau181. Results Plasma total tau and pTau181 levels were higher in AD dementia patients than those in cognitively unimpaired. Plasma pTau181 was more strongly associated with both Aβ and tau PET. Plasma pTau181 was a more sensitive and specific predictor of elevated brain Aβ than total tau and was as good as, or better than, the combination of age and apolipoprotein E ( APOE ). Discussion Plasma pTau181 may have utility as a biomarker of AD pathophysiology and as a noninvasive screener for elevated brain Aβ.

The cost of Alzheimer's disease in China and re-estimation of costs worldwide

Abstract: Introduction The socioeconomic costs of Alzheimer's disease (AD) in China and its impact on global economic burden remain uncertain. Methods We collected data from 3098 patients with AD in 81 representative centers across China and estimated AD costs for individual patient and total patients in China in 2015. Based on this data, we re-estimated the worldwide costs of AD. Results The annual socioeconomic cost per patient was US $19,144.36, and total costs were US $167.74 billion in 2015. The annual total costs are predicted to reach US $507.49 billion in 2030 and US $1.89 trillion in 2050. Based on our results, the global estimates of costs for dementia were US $957.56 billion in 2015, and will be US $2.54 trillion in 2030, and US $9.12 trillion in 2050, much more than the predictions by the World Alzheimer Report 2015. Discussion China bears a heavy burden of AD costs, which greatly change the estimates of AD cost worldwide.

Evidence for brain glucose dysregulation in Alzheimer's disease

Abstract: Introduction It is unclear whether abnormalities in brain glucose homeostasis are associated with Alzheimer's disease (AD) pathogenesis. Methods Within the autopsy cohort of the Baltimore Longitudinal Study of Aging, we measured brain glucose concentration and assessed the ratios of the glycolytic amino acids, serine, glycine, and alanine to glucose. We also quantified protein levels of the neuronal (GLUT3) and astrocytic (GLUT1) glucose transporters. Finally, we assessed the relationships between plasma glucose measured before death and brain tissue glucose. Results Higher brain tissue glucose concentration, reduced glycolytic flux, and lower GLUT3 are related to severity of AD pathology and the expression of AD symptoms. Longitudinal increases in fasting plasma glucose levels are associated with higher brain tissue glucose concentrations. Discussion Impaired glucose metabolism due to reduced glycolytic flux may be intrinsic to AD pathogenesis. Abnormalities in brain glucose homeostasis may begin several years before the onset of clinical symptoms.

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

Abstract: Introduction We forecast the prevalence of preclinical and clinical Alzheimer's disease (AD) and evaluated potential impacts of primary and secondary preventions in the United States. Methods We used a multistate model incorporating biomarkers for preclinical AD with US population projections. Results Approximately 6.08 million Americans had either clinical AD or mild cognitive impairment due to AD in 2017 and that will grow to 15.0 million by 2060. In 2017, 46.7 million Americans had preclinical AD (amyloidosis, neurodegeneration, or both), although many may not progress to clinical disease during their lifetimes. Primary and secondary preventions have differential impact on future disease burden. Discussion Because large numbers of persons are living with preclinical AD, our results underscore the need for secondary preventions for persons with existing AD brain pathology who are likely to develop clinical disease during their lifetimes as well as primary preventions for persons without preclinical disease.

The antimicrobial protection hypothesis of Alzheimer's disease.

Abstract: Objective We explore here a novel model for amyloidogenesis in Alzheimer's disease (AD). This new perspective on AD amyloidosis seeks to provide a rational framework for incorporating recent and seemingly independent findings on the antimicrobial role of β-amyloid and emerging experimental, genetic, and epidemiological data, suggesting innate immune-mediated inflammation propagates AD neurodegeneration. Background AD pathology is characterized by cerebral deposition of amyloid-β protein (Aβ) as β-amyloid. Genetic studies have confirmed the key role of Aβ in AD, revealing that mutation-mediated shifts in the peptides generation lead to early onset familial Alzheimer's disease. However, Aβ generation appears normal for the majority of AD patients, who lack early onset familial Alzheimer's disease mutations. In prevailing models of nonfamilial AD, individual genetics and age-associated changes in brain milieu promote an intrinsically abnormal propensity of Aβ for self-association. However, emerging findings are increasingly inconsistent with characterization of Aβ oligomerization as a nonphysiological and exclusively pathological activity. Recent studies suggest Aβ is an ancient, highly conserved effector molecule of innate immunity. Moreover, Aβ oligomerization and β-amyloid generation appear to be important innate immune pathways that mediate pathogen entrapment and protect against infection. New AD amyloidogenesis model Recent findings on inflammation-mediated neurodegeneration and the role of Aβ in immunity have led to emergence of the "Antimicrobial Protection Hypothesis" of AD. In this model, β-amyloid deposition is an early innate immune response to genuine, or mistakenly perceived, immunochallenge. Aβ first entraps and neutralizes invading pathogens in β-amyloid. Aβ fibrillization drives neuroinflammatory pathways that help fight the infection and clear β-amyloid/pathogen deposits. In AD, chronic activation of this pathway leads to sustained inflammation and neurodegeneration. Mounting data link elevated brain microbe levels with AD. The Antimicrobial Protection Hypothesis reveals how increased brain microbial burden may directly exacerbate β-amyloid deposition, inflammation, and AD progression. Amyloid cascade hypothesis In the antimicrobial protection model, the modality of Aβ's pathophysiology is shifted from abnormal stochastic behavior toward dysregulated innate immune response. However, β-amyloid deposition in AD still leads to neurodegeneration. Thus, the new model extends but remains broadly consistent with the Amyloid Cascade Hypothesis and overwhelming data showing the primacy of Aβ in AD pathology.

Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals

Abstract: Introduction Higher midlife body mass index (BMI) is suggested to increase the risk of dementia, but weight loss during the preclinical dementia phase may mask such effects. Methods We examined this hypothesis in 1,349,857 dementia-free participants from 39 cohort studies. BMI was assessed at baseline. Dementia was ascertained at follow-up using linkage to electronic health records (N = 6894). We assumed BMI is little affected by preclinical dementia when assessed decades before dementia onset and much affected when assessed nearer diagnosis. Results Hazard ratios per 5-kg/m 2 increase in BMI for dementia were 0.71 (95% confidence interval = 0.66–0.77), 0.94 (0.89–0.99), and 1.16 (1.05–1.27) when BMI was assessed 10 years, 10-20 years, and >20 years before dementia diagnosis. Conclusions The association between BMI and dementia is likely to be attributable to two different processes: a harmful effect of higher BMI, which is observable in long follow-up, and a reverse-causation effect that makes a higher BMI to appear protective when the follow-up is short.

Obesity trajectories and risk of dementia: 28 years of follow-up in the Whitehall II Study

Abstract: Introduction We examined whether obesity at ages 50, 60, and 70 years is associated with subsequent dementia. Changes in body mass index (BMI) for more than 28 years before dementia diagnosis were compared with changes in BMI in those free of dementia. Methods A total of 10,308 adults (33% women) aged 35 to 55 years in 1985 were followed up until 2015. BMI was assessed six times and 329 cases of dementia were recorded. Results Obesity (BMI ≥30 kg/m 2 ) at age 50 years (hazard ratio = 1.93; 1.35–2.75) but not at 60 or 70 years was associated with risk of dementia. Trajectories of BMI differed in those with dementia compared with all others ( P P P = .001) to 16 years ( P = .05) and lower starting 8 years before diagnosis. Discussion Obesity in midlife and weight loss in the preclinical phase characterizes dementia; the current obesity epidemic may affect future dementia rates.

Progress toward standardized diagnosis of vascular cognitive impairment: Guidelines from the Vascular Impairment of Cognition Classification Consensus Study

Abstract: Introduction Progress in understanding and management of vascular cognitive impairment (VCI) has been hampered by lack of consensus on diagnosis, reflecting the use of multiple different assessment protocols. A large multinational group of clinicians and researchers participated in a two-phase Vascular Impairment of Cognition Classification Consensus Study (VICCCS) to agree on principles (VICCCS-1) and protocols (VICCCS-2) for diagnosis of VCI. We present VICCCS-2. Methods We used VICCCS-1 principles and published diagnostic guidelines as points of reference for an online Delphi survey aimed at achieving consensus on clinical diagnosis of VCI. Results Six survey rounds comprising 65–79 participants agreed guidelines for diagnosis of VICCCS-revised mild and major forms of VCI and endorsed the National Institute of Neurological Disorders–Canadian Stroke Network neuropsychological assessment protocols and recommendations for imaging. Discussion The VICCCS-2 suggests standardized use of the National Institute of Neurological Disorders–Canadian Stroke Network recommendations on neuropsychological and imaging assessment for diagnosis of VCI so as to promote research collaboration.

Multidomain lifestyle intervention benefits a large elderly population at risk for cognitive decline and dementia regardless of baseline characteristics: The FINGER trial

Abstract: Introduction: The 2-year Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) multidomain lifestyle intervention trial (NCT01041989) demonstrated beneficial ...

Cerebrospinal fluid biomarkers measured by Elecsys assays compared to amyloid imaging.

Abstract: Introduction Levels of amyloid β peptide 42 (Aβ42), total tau, and phosphorylated tau-181 are well-established cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease, but variability in manual plate-based assays has limited their use. We examined the relationship between CSF biomarkers, as measured by a novel automated immunoassay platform, and amyloid positron emission tomography. Methods CSF samples from 200 individuals underwent separate analysis for Aβ42, total tau, and phosphorylated tau-181 with automated Roche Elecsys assays. Aβ40 was measured with a commercial plate-based assay. Positron emission tomography with Pittsburgh Compound B was performed less than 1 year from CSF collection. Results Ratios of CSF biomarkers (total tau/Aβ42, phosphorylated tau-181/Aβ42, and Aβ42/Aβ40) best discriminated Pittsburgh Compound B–positive from Pittsburgh Compound B–negative individuals. Discussion CSF biomarkers and amyloid positron emission tomography reflect different aspects of Alzheimer's disease brain pathology, and therefore, less-than-perfect correspondence is expected. Automated assays are likely to increase the utility of CSF biomarkers.

Stroke and dementia risk: A systematic review and meta-analysis

Abstract: Introduction Stroke is an established risk factor for all-cause dementia, though meta-analyses are needed to quantify this risk Methods We searched Medline, PsycINFO, and Embase for studies assessing prevalent or incident stroke versus a no-stroke comparison group and the risk of all-cause dementia Random effects meta-analysis was used to pool adjusted estimates across studies, and meta-regression was used to investigate potential effect modifiers Results We identified 36 studies of prevalent stroke (19 million participants) and 12 studies of incident stroke (13 million participants) For prevalent stroke, the pooled hazard ratio for all-cause dementia was 169 (95% confidence interval: 149–192; P 2 = 87%) For incident stroke, the pooled risk ratio was 218 (95% confidence interval: 190–250; P 2 = 88%) Study characteristics did not modify these associations, with the exception of sex which explained 502% of between-study heterogeneity for prevalent stroke Discussion Stroke is a strong, independent, and potentially modifiable risk factor for all-cause dementia

Blood-brain barrier breakdown, neuroinflammation, and cognitive decline in older adults

Abstract: Introduction Blood-brain barrier (BBB) breakdown is observed in older versus younger adults and in late-onset Alzheimer's disease versus age-matched controls, but its causes and consequences in aging are unclear. We tested the hypothesis that BBB breakdown is associated with cognitive decline and inflammation in nondemented elders. Methods Cerebrospinal fluid and serum inflammatory markers were measured using sandwich immunoassays in 120 subjects. Least Absolute Shrinkage and Selection Operator-logistic regression selected cerebrospinal fluid and serum signatures that best classified BBB impairment defined by the cerebrospinal fluid albumin index ≥9. Linear regression examined changes in Clinical Dementia Rating sum of boxes as a function of BBB integrity at baseline. Results Mean age was 70 years, mean Mini–Mental State Examination was 27, and BBB impairment was recorded in 13.5%. BBB breakdown was associated with cognitive decline ( P = .015). Cerebrospinal fluid intercellular adhesion molecule-1, vascular endothelial growth factor, interleukin-8, serum amyloid A, macrophage derived chemokine, and gender generated an area under the curve of 0.95 for BBB impairment, and serum IL-16, VEGF-D, IL-15, and other variables generated an AUC of 0.92 for BBB impairment. Discussion BBB breakdown is associated with more rapid cognitive decline. Inflammatory mechanisms, including cell adhesion, neutrophil migration, lipid metabolism, and angiogenesis may be implicated.

Sex, amyloid, and APOE ε4 and risk of cognitive decline in preclinical Alzheimer's disease: Findings from three well-characterized cohorts.

Abstract: Introduction Our objective was to investigate the effect of sex on cognitive decline within the context of amyloid β (Aβ) burden and apolipoprotein E genotype. Methods We analyzed sex-specific effects on Aβ-positron emission tomography, apolipoprotein, and rates of change on the Preclinical Alzheimer Cognitive Composite-5 across three cohorts, such as the Alzheimer's Disease Neuroimaging Initiative, Australian Imaging, Biomarker and Lifestyle, and Harvard Aging Brain Study (n = 755; clinical dementia rating = 0; age (standard deviation) = 73.6 (6.5); female = 55%). Mixed-effects models of cognitive change by sex, Aβ-positron emission tomography, and apolipoprotein e4 were examined with quadratic time effects over a median of 4 years of follow-up. Results Apolipoprotein e4 prevalence and Aβ burden did not differ by sex. Sex did not directly influence cognitive decline. Females with higher Aβ exhibited faster decline than males. Post hoc contrasts suggested that females who were Aβ and apolipoprotein e4 positive declined faster than their male counterparts. Discussion Although Aβ did not differ by sex, cognitive decline was greater in females with higher Aβ. Our findings suggest that sex may play a modifying role on risk of Alzheimer's disease–related cognitive decline.

Association of branched-chain amino acids and other circulating metabolites with risk of incident dementia and Alzheimer's disease: A prospective study in eight cohorts

Abstract: Introduction Metabolite, lipid, and lipoprotein lipid profiling can provide novel insights into mechanisms underlying incident dementia and Alzheimer's disease. Methods We studied eight prospective cohorts with 22,623 participants profiled by nuclear magnetic resonance or mass spectrometry metabolomics. Four cohorts were used for discovery with replication undertaken in the other four to avoid false positives. For metabolites that survived replication, combined association results are presented. Results Over 246,698 person-years, 995 and 745 cases of incident dementia and Alzheimer's disease were detected, respectively. Three branched-chain amino acids (isoleucine, leucine, and valine), creatinine and two very low density lipoprotein (VLDL)-specific lipoprotein lipid subclasses were associated with lower dementia risk. One high density lipoprotein (HDL; the concentration of cholesterol esters relative to total lipids in large HDL) and one VLDL (total cholesterol to total lipids ratio in very large VLDL) lipoprotein lipid subclass was associated with increased dementia risk. Branched-chain amino acids were also associated with decreased Alzheimer's disease risk and the concentration of cholesterol esters relative to total lipids in large HDL with increased Alzheimer's disease risk. Discussion Further studies can clarify whether these molecules play a causal role in dementia pathogenesis or are merely markers of early pathology.

Appropriate use criteria for lumbar puncture and cerebrospinal fluid testing in the diagnosis of Alzheimer's disease

Abstract: Introduction The Alzheimer's Association convened a multidisciplinary workgroup to develop appropriate use criteria to guide the safe and optimal use of the lumbar puncture procedure and cerebrospinal fluid (CSF) testing for Alzheimer's disease pathology detection in the diagnostic process. Methods The workgroup, experienced in the ethical use of lumbar puncture and CSF analysis, developed key research questions to guide the systematic review of the evidence and developed clinical indications commonly encountered in clinical practice based on key patient groups in whom the use of lumbar puncture and CSF may be considered as part of the diagnostic process. Based on their expertise and interpretation of the evidence from systematic review, members rated each indication as appropriate or inappropriate. Results The workgroup finalized 14 indications, rating 6 appropriate and 8 inappropriate. Discussion In anticipation of the emergence of more reliable CSF analysis platforms, the manuscript offers important guidance to health-care practitioners and suggestions for implementation and future research.

A systematic integrated analysis of brain expression profiles reveals YAP1 and other prioritized hub genes as important upstream regulators in Alzheimer's disease

Abstract: Introduction Profiling the spatial-temporal expression pattern and characterizing the regulatory networks of brain tissues are vital for understanding the pathophysiology of Alzheimer's disease (AD). Methods We performed a systematic integrated analysis of expression profiles of AD-affected brain tissues (684 AD and 562 controls). A network-based convergent functional genomic approach was used to prioritize possible regulator genes during AD development, followed by functional characterization. Results We generated a complete list of differentially expressed genes and hub genes of the transcriptomic network in AD brain and constructed a Web server (www.alzdata.org) for public access. Seventeen hub genes active at the early stages, especially YAP1 , were recognized as upstream regulators of the AD network. Cellular assays proved that early alteration of YAP1 could promote AD by influencing the whole transcriptional network. Discussion Early expression disturbance of hub genes is an important feature of AD development, and interfering with this process may reverse the disease progression.

Identifying dementia cases with routinely collected health data: A systematic review.

Abstract: Introduction Prospective, population-based studies can be rich resources for dementia research. Follow-up in many such studies is through linkage to routinely collected, coded health-care data sets. We evaluated the accuracy of these data sets for dementia case identification. Methods We systematically reviewed the literature for studies comparing dementia coding in routinely collected data sets to any expert-led reference standard. We recorded study characteristics and two accuracy measures—positive predictive value (PPV) and sensitivity. Results We identified 27 eligible studies with 25 estimating PPV and eight estimating sensitivity. Study settings and methods varied widely. For all-cause dementia, PPVs ranged from 33%–100%, but 16/27 were >75%. Sensitivities ranged from 21% to 86%. PPVs for Alzheimer's disease (range 57%–100%) were generally higher than those for vascular dementia (range 19%–91%). Discussion Linkage to routine health-care data can achieve a high PPV and reasonable sensitivity in certain settings. Given the heterogeneity in accuracy estimates, cohorts should ideally conduct their own setting-specific validation.

Elevated DNA methylation across a 48-kb region spanning the HOXA gene cluster is associated with Alzheimer's disease neuropathology

Abstract: Introduction Alzheimer's disease is a neurodegenerative disorder that is hypothesized to involve epigenetic dysregulation of gene expression in the brain. Methods We performed an epigenome-wide association study to identify differential DNA methylation associated with neuropathology in prefrontal cortex and superior temporal gyrus samples from 147 individuals, replicating our findings in two independent data sets (N = 117 and 740). Results We identify elevated DNA methylation associated with neuropathology across a 48-kb region spanning 208 CpG sites within the HOXA gene cluster. A meta-analysis of the top-ranked probe within the HOXA3 gene (cg22962123) highlighted significant hypermethylation across all three cohorts ( P = 3.11 × 10 −18 ). Discussion We present robust evidence for elevated DNA methylation associated with Alzheimer's disease neuropathology spanning the HOXA gene cluster on chromosome 7. These data add to the growing evidence highlighting a role for epigenetic variation in Alzheimer's disease, implicating the HOX gene family as a target for future investigation.

Coronary heart disease, heart failure, and the risk of dementia: A systematic review and meta-analysis.

Abstract: Introduction Cardiovascular risk factors are closely linked with dementia risk, but whether heart disease predisposes to dementia is uncertain. Methods We systematically reviewed the literature and meta-analyzed risk estimates from longitudinal studies reporting the association of coronary heart disease (CHD) or heart failure (HF) with risk of dementia. Results We identified 16 studies (1,309,483 individuals) regarding CHD, and seven studies (1,958,702 individuals) about HF. A history of CHD was associated with a 27% increased risk of dementia (pooled relative risk [RR] [95% confidence interval, CI]: 1.27 [1.07–1.50]), albeit with considerable heterogeneity across studies (I 2 = 80%). HF was associated with 60% increased dementia risk (pooled RR 1.60 [1.19–2.13]) with moderate heterogeneity (I 2 = 59%). Among prospective population-based cohorts, pooled estimates were similar (for CHD, RR 1.26 [1.06–1.49], nine studies; and HF, RR 1.80 [1.41–2.31], four studies) and highly consistent (I 2 = 0%). Conclusion CHD and HF are associated with an increased risk of dementia.

Inflammatory markers and the risk of dementia and Alzheimer's disease: A meta-analysis.

Abstract: Introduction Inflammatory markers are often elevated in patients with dementia, including Alzheimer's disease (AD). However, it remains unclear whether inflammatory markers are associated with the risk of developing dementia. Methods We searched PubMed, Embase, and Cochrane library for prospective population-based studies reporting associations between inflammatory markers and all-cause dementia or AD. We used random effects meta-analyses to obtain pooled hazard ratios (HRs) and 95% confidence intervals of inflammatory markers (highest vs. lowest quantile) for all-cause dementia and AD. Results Fifteen articles from 13 studies in six countries reported data that could be meta-analyzed. C-reactive protein (HR = 1.37 [1.05; 1.78]), interleukin-6 (HR = 1.40 [1.13; 1.73]), α1-antichymotrypsin (HR = 1.54 [1.14; 2.80]), lipoprotein-associated phospholipase A2 activity (HR = 1.40 [1.03; 1.90]), and fibrinogen were each associated with all-cause dementia, but neither was significantly associated with AD. Discussion Several inflammatory markers are associated with an increased risk of all-cause dementia; however, these markers are not specific for AD. Whether inflammatory markers closely involved in AD pathology are associated with the risk of AD remains to be elucidated.

Concomitant vascular and neurodegenerative pathologies double the risk of dementia

Abstract: Introduction The relative contributions of vascular and degenerative pathology to dementia are unknown. We aim to quantify the proportion of dementia explained by potentially preventable vascular lesions. Methods We systematically searched for population-based cohorts before February 2017 reporting clinicopathological data for individuals with and without dementia. We calculated the summary proportion and absolute risk of dementia comparing subjects with and without the pathology. Results We identified 10 studies comprising 2856 subjects. Vascular-type pathology and mixed pathology are respectively two and three times more likely in demented patients. The summary proportion of dementia is 77%–86% in subjects with mixed degenerative and vascular pathology and 45% in subjects with pure Alzheimer-type pathology. Discussion Patients with mixed pathologies have nearly twice the incremental risk of dementia compared with patients with only Alzheimer-type lesions. Consequently, many cases of dementia could be prevented or delayed by targeting the vascular component.

Circulating metabolites and general cognitive ability and dementia : Evidence from 11 cohort studies

Abstract: Introduction Identifying circulating metabolites that are associated with cognition and dementia may improve our understanding of the pathogenesis of dementia and provide crucial readouts for preventive and therapeutic interventions. Methods We studied 299 metabolites in relation to cognition (general cognitive ability) in two discovery cohorts (N total = 5658). Metabolites significantly associated with cognition after adjusting for multiple testing were replicated in four independent cohorts (N total = 6652), and the associations with dementia and Alzheimer's disease (N = 25,872) and lifestyle factors (N = 5168) were examined. Results We discovered and replicated 15 metabolites associated with cognition including subfractions of high-density lipoprotein, docosahexaenoic acid, ornithine, glutamine, and glycoprotein acetyls. These associations were independent of classical risk factors including high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, glucose, and apolipoprotein E (APOE) genotypes. Six of the cognition-associated metabolites were related to the risk of dementia and lifestyle factors. Discussion Circulating metabolites were consistently associated with cognition, dementia, and lifestyle factors, opening new avenues for prevention of cognitive decline and dementia.

Conserved brain myelination networks are altered in Alzheimer's and other neurodegenerative diseases

Abstract: Introduction Comparative transcriptome analyses in Alzheimer's disease (AD) and other neurodegenerative proteinopathies can uncover both shared and distinct disease pathways. Methods We analyzed 940 brain transcriptomes including patients with AD, progressive supranuclear palsy (PSP; a primary tauopathy), and control subjects. Results We identified transcriptional coexpression networks implicated in myelination, which were lower in PSP temporal cortex (TCX) compared with AD. Some of these associations were retained even after adjustments for brain cell population changes. These TCX myelination network structures were preserved in cerebellum but they were not differentially expressed in cerebellum between AD and PSP. Myelination networks were downregulated in both AD and PSP, when compared with control TCX samples. Discussion Downregulation of myelination networks may underlie both PSP and AD pathophysiology, but may be more pronounced in PSP. These data also highlight conservation of transcriptional networks across brain regions and the influence of cell type changes on these networks.

Cerebral small vessel disease and the risk of dementia: A systematic review and meta-analysis of population-based evidence.

Abstract: Introduction Cerebral small vessel disease is increasingly linked to dementia. Methods We systematically searched Medline, Embase, and Cochrane databases for prospective population-based studies addressing associations of white matter hyperintensities, covert brain infarcts (i.e., clinically silent infarcts), and cerebral microbleeds with risk of all-dementia or Alzheimer's disease and performed meta-analyses. Results We identified 11 studies on white matter hyperintensities, covert brain infarcts, or cerebral microbleeds with risk of all-dementia or Alzheimer's disease. Pooled analyses showed an association of white matter hyperintensity volume and a borderline association of covert brain infarcts with risk of all-dementia (hazard ratio: 1.39 [95% confidence interval: 1.00; 1.94], N = 3913, and 1.47 [95% confidence interval: 0.97; 2.22], N = 8296). Microbleeds were not statistically significantly associated with an increased risk of all-dementia (hazard ratio: 1.25 [95% confidence interval: 0.66; 2.38], N = 8739). Discussion White matter hyperintensities are associated with an increased risk of all-dementia and Alzheimer's disease in the general population. However, studies are warranted to further determine the role of markers of cerebral small vessel disease in dementia.

Free water determines diffusion alterations and clinical status in cerebral small vessel disease.

Abstract: Introduction Diffusion tensor imaging detects early tissue alterations in Alzheimer's disease and cerebral small vessel disease (SVD). However, the origin of diffusion alterations in SVD is largely unknown. Methods To gain further insight, we applied free water (FW) imaging to patients with genetically defined SVD (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy [CADASIL], n = 57), sporadic SVD (n = 444), and healthy controls (n = 28). We modeled freely diffusing water in the extracellular space (FW) and measures reflecting fiber structure (tissue compartment). We tested associations between these measures and clinical status (processing speed and disability). Results Diffusion alterations in SVD were mostly driven by increased FW and less by tissue compartment alterations. Among imaging markers, FW showed the strongest association with clinical status (R 2 up to 34%, P Discussion Diffusion alterations and clinical status in SVD are largely determined by extracellular fluid increase rather than alterations of white matter fiber organization.

Longitudinal decreases in multiple cerebrospinal fluid biomarkers of neuronal injury in symptomatic late onset Alzheimer's disease.

Abstract: Introduction Individuals in early stages of Alzheimer's disease are a targeted population for secondary prevention trials aimed at preserving normal cognition. Understanding within-person biomarker(s) change over time is critical for trial enrollment and design. Methods Longitudinal cerebrospinal fluid samples from the Alzheimer's Disease Neuroimaging Initiative were assayed for novel markers of neuronal/synaptic injury (visinin-like protein 1, Ng, and SNAP-25) and neuroinflammation (YKL-40) and compared with β amyloid 42, tau, and phospho-tau181. General linear mixed models were used to compare within-person rates of change in three clinical groups (cognitively normal, mild cognitive impairment, and Alzheimer's disease) further defined by β amyloid status. Results Levels of injury markers were highly positively correlated. Despite elevated baseline levels as a function of clinical status and amyloid-positivity, within-person decreases in these measures were observed in the early symptomatic, amyloid-positive Alzheimer's disease group. Discussion Knowledge of within-person biomarker change will impact interpretation of biomarker outcomes in clinical trials that are dependent on disease stage.

Polygenic risk score of sporadic late-onset Alzheimer's disease reveals a shared architecture with the familial and early-onset forms.

Abstract: Objective To determine whether the extent of overlap of the genetic architecture among the sporadic late-onset Alzheimer's Disease (sLOAD), familial late-onset AD (fLOAD), sporadic early-onset AD (sEOAD), and autosomal dominant early-onset AD (eADAD). Methods Polygenic risk scores (PRSs) were constructed using previously identified 21 genome-wide significant loci for LOAD risk. Results We found that there is an overlap in the genetic architecture among sEOAD, fLOAD, and sLOAD. The highest association of the PRS and risk (odds ratio [OR] = 2.27; P = 1.29 × 10 −7 ) was observed in sEOAD, followed by fLOAD (OR = 1.75; P = 1.12 × 10 −7 ) and sLOAD (OR = 1.40; P = 1.21 × 10 −3 ). The PRS was associated with cerebrospinal fluid ptau 181 -Aβ 42 on eADAD ( P = 4.36 × 10 −2 ). Conclusion Our analysis confirms that the genetic factors identified for LOAD modulate risk in sLOAD and fLOAD and also sEOAD cohorts. Specifically, our results suggest that the burden of these risk variants is associated with familial clustering and earlier onset of AD. Although these variants are not associated with risk in the eADAD, they may be modulating age at onset.