Practical recommendations for timely, accurate diagnosis of symptomatic Alzheimer's disease (MCI and dementia) in primary care: a review and synthesis.

The critical role of primary care clinicians (PCCs) in Alzheimer's disease (AD) prevention, diagnosis and management must evolve as new treatment paradigms and disease-modifying therapies (DMTs) emerge. Our understanding of AD has grown substantially: no longer conceptualized as a late-in-life syndrome of cognitive and functional impairments, we now recognize that AD pathology builds silently for decades before cognitive impairment is detectable. Clinically, AD first manifests subtly as mild cognitive impairment (MCI) due to AD before progressing to dementia. Emerging optimism for improved outcomes in AD stems from a focus on preventive interventions in midlife and timely, biomarker-confirmed diagnosis at early signs of cognitive deficits (i.e. MCI due to AD and mild AD dementia). A timely AD diagnosis is particularly important for optimizing patient care and enabling the appropriate use of anticipated DMTs. An accelerating challenge for PCCs and AD specialists will be to respond to innovations in diagnostics and therapy for AD in a system that is not currently well positioned to do so. To overcome these challenges, PCCs and AD specialists must collaborate closely to navigate and optimize dynamically evolving AD care in the face of new opportunities. In the spirit of this collaboration, we summarize here some prominent and influential models that inform our current understanding of AD. We also advocate for timely and accurate (i.e. biomarker-defined) diagnosis of early AD. In doing so, we consider evolving issues related to prevention, detecting emerging cognitive impairment and the role of biomarkers in the clinic.

GBA mutations in Parkinson disease: earlier death but similar neuropathological features.

BACKGROUND AND PURPOSE: Mutations in the glucocerebrosidase (GBA) gene are known to be a risk factor for Parkinson's disease (PD). Data on clinicopathological correlation are limited. The purpose of this study was to determine the clinicopathological findings that might distinguish PD cases with and without mutations in the GBA gene. METHODS: Data from the Arizona Study of Aging and Neurodegenerative Disorders were used to identify autopsied PD cases that did or did not have a GBA gene mutation. Clinical and neuropathological data were compared. RESULTS: Twelve PD cases had a GBA mutation and 102 did not. The GBA mutation cases died younger (76 vs. 81 years of age) but there was no difference in disease duration or clinical examination findings. No neuropathological differences were found in total or regional semi-quantitative scores for Lewy-type synucleinopathy, senile plaques, neurofibrillary tangles, white matter rarefaction or cerebral amyloid angiopathy scores. CONCLUSIONS: In longitudinally assessed, autopsied PD cases, those with GBA mutations had a younger age at death but there was no evidence for clinical or neuropathological differences compared to cases without GBA mutations. Due to the small GBA group size, small differences cannot be excluded.

Differential spectral quantitative electroencephalography patterns between control and Parkinson's disease cohorts.

BACKGROUND AND PURPOSE: It is believed that progressive Lewy-type synucleinopathy (LTS) is primarily responsible for the worsening of motor and non-motor Parkinson's disease (PD) signs and symptoms. Characterization of quantitative electroencephalography (QEEG) abnormalities across the spectrum of LTS to PD dementia (PD-D) may provide insight into the pathophysiology of PD cortical dysfunction. Here our enlarged EEG database was leveraged to characterize spectral QEEG abnormalities in asymptomatic autopsy-defined groups of control participants and incidental Lewy body disease (ILBD) and three clinically defined groups of participants with PD (cognitively normal PD, mild cognitive impairment PD, and PD-D). METHODS: The PD cohort was studied as part of the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). AZSAND utilizes its Brain and Body Donation Program to perform prospective, standardized, regular longitudinal pre-mortem assessments until death. Resting EEG from subjects was analyzed for spectral domain QEEG measures of background rhythm frequency and global relative power in delta, theta, alpha and beta bands. RESULTS: The various spectral QEEG measures showed differential changes specific to the groups compared. Important findings were background rhythm frequency showing the most pairwise differences across the groups, and this also was the only significant difference between control and ILBD. An increase in delta bandpower was characteristic of worsening cognitive deficits. CONCLUSIONS: Different patterns of change amongst QEEG measures across LTS and PD cognitive states suggest that they correlate with heterogeneous pathophysiologies of cortical dysfunction within the PD clinical spectrum. In addition, the biomarker application of a specific spectral QEEG measure needs to be selectively suited to its study purpose.

Florbetapir F 18 amyloid PET and 36-month cognitive decline: a prospective multicenter study.

This study was designed to evaluate whether subjects with amyloid beta (Aß) pathology, detected using florbetapir positron emission tomorgraphy (PET), demonstrated greater cognitive decline than subjects without Aß pathology. Sixty-nine cognitively normal (CN) controls, 52 with recently diagnosed mild cognitive impairment (MCI) and 31 with probable Alzheimer's disease (AD) dementia were included in the study. PET images obtained in these subjects were visually rated as positive (Aß+) or negative (Aß-), blind to diagnosis. Fourteen percent (10/69) of CN, 37% (19/52) of MCI and 68% (21/31) of AD were Aß+. The primary outcome was change in ADAS-Cog score in MCI subjects after 36 months; however, additional outcomes included change on measures of cognition, function and diagnostic status. Aß+ MCI subjects demonstrated greater worsening compared with Aß- subjects on the ADAS-Cog over 36 months (5.66 ± 1.47 vs -0.71 ± 1.09, P = 0.0014) as well as on the mini-mental state exam (MMSE), digit symbol substitution (DSS) test, and a verbal fluency test (P < 0.05). Similar to MCI subjects, Aß+ CN subjects showed greater decline on the ADAS-Cog, digit-symbol-substitution test and verbal fluency (P<0.05), whereas Aß+ AD patients showed greater declines in verbal fluency and the MMSE (P < 0.05). Aß+ subjects in all diagnostic groups also showed greater decline on the CDR-SB (P<0.04), a global clinical assessment. Aß+ subjects did not show significantly greater declines on the ADCS-ADL or Wechsler Memory Scale. Overall, these findings suggest that in CN, MCI and AD subjects, florbetapir PET Aß+ subjects show greater cognitive and global deterioration over a 3-year follow-up than Aß- subjects do.

Impact of beta-amyloid-specific florbetaben PET imaging on confidence in early diagnosis of Alzheimer's disease.

BACKGROUND: Early diagnosis of Alzheimer's disease (AD) may be corroborated by imaging of beta-amyloid plaques using positron emission tomography (PET). Here, we performed an add-on questionnaire study to evaluate the relevance of florbetaben imaging (BAY 949172) in diagnosis and consecutive management of probable AD patients. METHODS: AD patients with a clinical diagnosis in accordance with the NINCDS-ADRDA criteria or controls were imaged using florbetaben. Referring physicians were asked on a voluntary basis about their confidence in initial diagnosis, significance of PET imaging results, and their anticipated consequences for future patient care. RESULTS: 121 questionnaires for probable AD patients and 80 questionnaires for controls were evaluated. In 18% of patients who had initially received the diagnosis of probable AD, PET scans were rated negative, whereas in controls 18% of scans were positive. An increase in confidence in the initial diagnosis was frequently reported (80%). Imaging results had a significant impact on the intended patient care, as judged by the referring physicians; this was most prominent in those patients with a contradicting scan and/or a low confidence in the initial diagnosis. CONCLUSION: Florbetaben amyloid imaging increases the overall confidence in diagnosis of AD and may frequently influence clinical decisions and patient management.

Diagnosis of Early Alzheimer's Disease: Clinical Practice in 2021.

Alzheimer's disease is a progressive, irreversible neurodegenerative disease impacting cognition, function, and behavior. Alzheimer's disease progresses along a continuum from preclinical disease, to mild cognitive and/or behavioral impairment and then Alzheimer's disease dementia. Recently, clinicians have been encouraged to diagnose Alzheimer's earlier, before patients have progressed to Alzheimer's disease dementia. The early and accurate detection of Alzheimer's disease-associated symptoms and underlying disease pathology by clinicians is fundamental for the screening, diagnosis, and subsequent management of Alzheimer's disease patients. It also enables patients and their caregivers to plan for the future and make appropriate lifestyle changes that could help maintain their quality of life for longer. Unfortunately, detecting early-stage Alzheimer's disease in clinical practice can be challenging and is hindered by several barriers including constraints on clinicians' time, difficulty accurately diagnosing Alzheimer's pathology, and that patients and healthcare providers often dismiss symptoms as part of the normal aging process. As the prevalence of this disease continues to grow, the current model for Alzheimer's disease diagnosis and patient management will need to evolve to integrate care across clinical disciplines and the disease continuum, beginning with primary care. This review summarizes the importance of establishing an early diagnosis of Alzheimer's disease, related practical 'how-to' guidance and considerations, and tools that can be used by healthcare providers throughout the diagnostic journey.

Examining the Role of Microbiota in Emotional Behavior: Antibiotic Treatment Exacerbates Anxiety in High Anxiety-Prone Male Rats.

Intestinal microbiota are essential for healthy gastrointestinal function and also broadly influence brain function and behavior, in part, through changes in immune function. Gastrointestinal disorders are highly comorbid with psychiatric disorders, although biological mechanisms linking these disorders are poorly understood. The present study utilized rats bred for distinct emotional behavior phenotypes to examine relationships between emotionality, the microbiome, and immune markers. Prior work showed that Low Novelty Responder (LR) rats exhibit high levels of anxiety- and depression-related behaviors as well as myriad neurobiological differences compared to High Novelty Responders (HRs). Here, we hypothesized that the divergent HR/LR phenotypes are accompanied by changes in fecal microbiome composition. We used next-generation sequencing to assess the HR/LR microbiomes and then treated adult HR/LR males with an antibiotic cocktail to test whether it altered behavior. Given known connections between the microbiome and immune system, we also analyzed circulating cytokines and metabolic factors to determine relationships between peripheral immune markers, gut microbiome components, and behavioral measures. There were no baseline HR/LR microbiome differences, and antibiotic treatment disrupted the microbiome in both HR and LR rats. Antibiotic treatment exacerbated aspects of HR/LR behavior, increasing LRs' already high levels of anxiety-like behavior while reducing passive stress coping in both strains. Our results highlight the importance of an individual's phenotype to their response to antibiotics, contributing to the understanding of the complex interplay between gut microbes, immune function, and an individual's emotional phenotype.

Early Detection of Mild Cognitive Impairment (MCI) in Primary Care.

Mild cognitive impairment (MCI) is significantly misdiagnosed in the primary care setting due to multi-dimensional frictions and barriers associated with evaluating individuals' cognitive performance. To move toward large-scale cognitive screening, a global panel of clinicians and cognitive neuroscientists convened to elaborate on current challenges that hamper widespread cognitive performance assessment. This report summarizes a conceptual framework and provides guidance to clinical researchers and test developers and suppliers to inform ongoing refinement of cognitive evaluation. This perspective builds upon a previous article in this series, which outlined the rationale for and potentially against efforts to promote widespread detection of MCI. This working group acknowledges that cognitive screening by default is not recommended and proposes large-scale evaluation of individuals with a concern or interest in their cognitive performance. Such a strategy can increase the likelihood to timely and effective identification and management of MCI. The rising global incidence of AD demands innovation that will help alleviate the burden to healthcare systems when coupled with the potentially near-term approval of disease-modifying therapies. Additionally, we argue that adequate infrastructure, equipment, and resources urgently should be integrated in the primary care setting to optimize the patient journey and accommodate widespread cognitive evaluation.

Early Detection of Mild Cognitive Impairment (MCI) in an At-Home Setting.

Emerging digital tools have the potential to enable a new generation of qualitative and quantitative assessment of cognitive performance. Moreover, the ubiquity of consumer electronics, such as smartphones and tablets, can be harnessed to support large-scale self-assessed cognitive screening with benefit to healthcare systems and consumers. A wide variety of apps, wearables, and new digital technologies are either available or in development for the detection of mild cognitive impairment (MCI), a risk factor for dementia. Two categories of novel methodologies may be considered: passive technologies (which monitor a user's behavior without active user input) and interactive assessments (which require active user input). Such examinations can be self-administered, supervised by a caregiver, or conducted by an informant at home or outside of a clinical setting. These direct-to-consumer tools have the potential to sidestep barriers associated with cognitive evaluation in primary care, thus improving access to cognitive assessments. Although direct-to-consumer cognitive assessment is associated with its own barriers, including test validation, user experience, and technological concerns, it is conceivable that these issues can be addressed so that a large-scale, self-assessed cognitive evaluation that would represent an initial cognitive screen may be feasible in the future.

Rationale for Early Diagnosis of Mild Cognitive Impairment (MCI) Supported by Emerging Digital Technologies.

Disease-modifying pharmacotherapies for Alzheimer's Disease (AD) are currently in late-stage clinical development; once approved, new healthcare infrastructures and services, including primary healthcare, will be necessary to accommodate a huge demand for early and large-scale detection of AD. The increasing global accessibility of digital consumer electronics has opened up new prospects for early diagnosis and management of mild cognitive impairment (MCI) with particular regard to AD. This new wave of innovation has spurred research in both academia and industry, aimed at developing and validating a new "digital generation" of tools for the assessment of the cognitive performance. In light of this paradigm shift, an international working group (the Global Advisory Group on Future MCI Care Pathways) convened to elaborate on how digital tools may be optimally integrated in screening-diagnostic pathways of AD The working group developed consensus perspectives on new algorithms for large-scale screening, detection, and diagnosis of individuals with MCI within primary medical care delivery. In addition, the expert panel addressed operational aspects concerning the implementation of unsupervised at-home testing of cognitive performance. The ultimate intent of the working group's consensus perspectives is to provide guidance to developers of cognitive tests and tools to facilitate the transition toward globally accessible cognitive screening aimed at the early detection, diagnosis, and management of MCI due to AD.

Both early and late cognitive dysfunction affects the electroencephalogram in Parkinson's disease.

We sought to define quantitative electroencephalographic (EEG) measures as biomarkers of both early and late cognitive decline in Parkinson's disease (PD). PD subjects classified as cognitively normal (PD-CogNL), mild cognitive impairment (PD-MCI), and dementia (PD-D) were studied. Cognitive status and neuropsychological testing was correlated with background rhythm and frequency band EEG power across five frequency bands. We conclude that global EEG measures have potential use as biomarkers in the study of both early and late cognitive deterioration in PD, including for evaluating its treatment. PD-MCI has mean quantitative EEG characteristics that represent an intermediate electrophysiological state between PD-CogNL and PD-D.

Pathological correlates of cognitive decline in Alzheimer's disease.

Although Alzheimer's disease (AD) has been investigated for more than 100 years, it was not until the 60s that quantitative measures of the disease progression and severity in relation to function and neuropathology were made by Blessed and his colleagues. With the increasing understanding of the pathological changes of AD that take place, there is growing interest in identifying which pathological marker most reliably predicts the dementia and the cognitive profile. Markers of pathology that have been investigated include senile plaques, neurofibrillary tangles, synaptic loss, and neurochemical changes. Many clinical measures have been evaluated as well including Clinical Dementia Rating, Mini Mental State Examination, and Functional Assessment Staging as ways of both predicting the presence of pathological changes of AD as well as correlating with the specific measures of pathology. Accumulation of neuropathology appears to correlate with functional, global, and cognitive decline as people progress through AD. This review will summarize evidence of which neuropathological change correlates robustly with cognitive decline and which cognitive index predicts pathological changes in AD. In general, tangles and synaptic loss are better correlates of cognitive decline and correlate better.

Circulating cholesterol levels, apolipoprotein E genotype and dementia severity influence the benefit of atorvastatin treatment in Alzheimer's disease: results of the Alzheimer's Disease Cholesterol-Lowering Treatment (ADCLT) trial.

CONTEXT: Recent evidence suggests that treatment of mild-to-moderate Alzheimer's disease (AD) with atorvastatin provides significant benefit on the Alzheimer Disease Assessment Scale-Cognitive (ADAS-cog) after 6 months. OBJECTIVE: To determine if benefit on ADAS-cog performance produced by atorvastatin is influenced by severity of cognitive impairment, circulating cholesterol levels, or apolipoprotein E genotype. DESIGN: A double-blind, placebo-controlled, randomized (1:1) trial with a 1-year exposure to atorvastatin calcium or placebo. SETTING: A single-site study at the clinical research center of the Sun Health Research Institute. PARTICIPANTS: Ninety-eight individuals with mild-to-moderate AD (MMSE score of 12-28) provided informed consent, and 67 were randomized. Stable dose use of cholinesterase inhibitors, estrogen and vitamin E was allowed, as was the use of many other medications in the treatment of co-morbidities. Participants using cholesterol-lowering medications or being treated for major depression or a psychiatric condition were excluded. INTERVENTION: Once daily atorvastatin calcium (80 mg; two 40 mg tablets) or placebo. MAIN OUTCOME MEASURES: A primary outcome measure was change ADAS-cog sub-scale score. Secondary outcome measures included scores on the MMSE, and circulating cholesterol levels. The Apolipoprotein E genotype was established for each participant. RESULTS: A significant positive effect on ADAS-cog performance occurred after 6 months of atorvastatin therapy compared with placebo. This positive effect was more prominent among individuals entering the trial with, (i) higher MMSE scores, (ii) cholesterol levels above 200 mg/dl or (iii) if they harbored an apolipoprotein-E-4 allele compared with participants not responding to atorvastatin treatment. Individuals in the placebo group tended to experience more pronounced deterioration if their cholesterol levels exceeded 200 mg/dl or they harbored an apolipoprotein-E-4 allele. CONCLUSION: Atorvastatin therapy may be of benefit in the treatment of mild-to-moderately affected AD patients, but the level of benefit produced may be predicated on earlier treatment, an individual's apolipoprotein E genotype or whether the patient exhibits elevated cholesterol levels.

Is the functional decline of Parkinson's disease similar to the functional decline of Alzheimer's disease?

Since many Parkinson's disease (PD) subjects develop dementia, we determined whether the correlation between functional and cognitive decline seen in Alzheimer's disease (AD) is seen in PD. Seventy-five PD subjects with and without dementia and 103 AD/MCI subjects underwent the Functional Assessment Staging (FAST), the Global Deterioration Scale (GDS), the UPDRS motor portion, and the MMSE. In AD/MCI subjects, changes in FAST and GDS scores correlated with MMSE (rho=-0.814, P<0.001; rho=-0.840, P<0.001, respectively). In PD subjects, the FAST and GDS also correlated with MMSE (rho=-0.675, P<0.001; rho=-0.647, P<0.001, respectively). The UPDRS correlated with the GDS and FAST more closely in PD than in AD. Similar to AD, functional declines in PD correlates with cognitive decline and may be influenced by motor disability in PD.

Nicotinic receptor losses in dementia with Lewy bodies: comparisons with Alzheimer's disease.

We sought to delineate differences between alpha7 nicotinic acetylcholine receptor (nAChR) levels in Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and age matched controls, as well as the correlations between alpha7 or non-alpha7 nAChR levels and synaptophysin (Syn) or choline acetyltransferase (ChAT) in DLB. Mean bungarotoxin (Bgt) binding was 2.7 - 1.1 for controls, 2.4 +/- 1.0 for AD and 1.4 +/- 0.5 for DLB. There were significant decreases in Bgt binding for the DLB group compared to either controls or AD. Mean epibatidine (Epi) binding was 14.8 +/- 3.2 for controls, 6.3 +/- 3.2 for AD and 7.1 +/- 2.4 fmoles/mg protein for DLB. Epi binding in both the AD and DLB groups was significantly lower than in the controls. Although Syn loss correlated with the decrease in Epi binding in both diseases, declining ChAT levels correlated with Epi binding only in DLB. These data demonstrate a different pattern of nAChR loss in AD and DLB that may, in part, explain some of the differences in the two phenotypes.

Neurochemical markers do not correlate with cognitive decline in the Lewy body variant of Alzheimer disease.

BACKGROUND: Reductions in neocortical synapses and cholinergic function occur in patients with Alzheimer disease (AD) and in patients with the Lewy body variant of AD (LBV). The relation between these losses and cognitive decline has been reported frequently in patients with AD but remains unclear for patients with LBV. OBJECTIVES: To investigate the relation between clinical markers of disease progression and choline acetyltransferase activity or synaptic density, measured by synaptophysin (Syn) level, in patients with LBV, and to investigate the relation of these neurochemical markers with one another. METHODS: Brain specimens of 41 patients with autopsy-confirmed (National Institute on Aging criteria for AD) LBV were examined. The last Mini-Mental State Examination and Blessed Information-Memory-Concentration test scores before death were reviewed. Midfrontal synapse counts were quantified by a dot-immunobinding assay for Syn. Choline acetyltransferase activity of the midfrontal cortex was assayed by established protocols. RESULTS: The last Mini-Mental State Examination score before death did not correlate significantly with Syn level (n = 25, r = 0.25, P = .24); however, there was a trend toward significance for the relation between last Mini-Mental State Examination score and choline acetyltransferase activity (n = 39, r = 0.31, P = .05). The last Blessed Information-Memory-Concentration test score did not correlate with either Syn level (n = 24, r = -0.17, P = .44) or choline acetyltransferase activity (n = 39, r = -0.16, P = .33). Finally, there was only a modest correlation between Syn level and choline acetyltransferase activity (n = 25, r = 0.38, P = .06), which did not reach statistical significance. CONCLUSION: Unlike AD, neurochemical markers do not appear to correlate well with cognitive decline in LBV.

The impact of apolipoprotein E4 on cause of death in Alzheimer's disease.

OBJECTIVE: We tested the hypothesis that the apolipoprotein E epsilon 4 (apoE4) allele is associated with an increased proportion of vascular-related mortality in Alzheimer's disease (AD). BACKGROUND: ApoE4 is associated with an increased risk of developing AD, with an earlier onset, and may predispose to vascular dementia as well. In the general population, apoE4 has been associated with increased coronary artery disease and shorter lifespan. There is a paucity of data regarding the effect of the apolipoprotein E (apoE) genotype upon the contributing causes of death in AD. METHODS: Death certificates of 114 AD cases were reviewed blind to apoE genotype. Deaths due to ischemic heart disease (IHD), cerebrovascular disease (CVD), vascular disease (either IHD or CVD), pneumonia, and other causes were analyzed as a function of apoE genotype. Logistic regression analyses were employed to control for age and gender effects. RESULTS: The likelihood of vascular disease contributing to death increased in association with the epsilon 4 allele (29% in cases without an epsilon 4 allele, 43% in cases with one epsilon 4 allele, 53% in epsilon 4/4 homozygous cases; p = 0.035 after corrections for age and gender). This increase appeared largely due to an increase in ischemic heart disease, which was reported more frequently on death certificates of cases with one or more epsilon 4 allele (adjusted odds ratio [OR] = 1.85 per epsilon 4 allele; p < 0.05). There were nonsignificant trends for apoE4 to be associated with increased mortality related to cerebrovascular disease (OR = 1.45) and decreased mortality related to pneumonia (OR = 0.77) and AD itself (OR = 0.72). The epsilon 4/4 cases had significantly earlier age of onset (mean = 64.5 yr), earlier death, and longer duration of disease (mean = 10.1 yr). Cases with one or more epsilon 4 allele tended to have lower mean MMSE scores prior to death (6.6 versus 9.5) and were more often female (54% versus 45%). CONCLUSIONS: The apoE4 allele appears to increase the risk of vascular and ischemic heart disease-related death in patients with AD.

Hippocampal sclerosis contributes to dementia in the elderly.

OBJECTIVE: To assess the relevance of hippocampal sclerosis (HS) to dementia in the elderly. BACKGROUND: HS is a prominent pathologic finding in some demented elderly, but the anatomic substrate and cognitive profiles of this dementia have not been well established. DESIGN/METHODS: An autopsy series, including dot-immunobinding assay to estimate neocortical synaptic density, of eight patients (three men, five women) with HS on whom extensive antemortem neuropsychological testing was available. RESULTS: Mean age at onset was 72.0 (+/-9.8) (range, 59 to 89) with a mean duration of symptoms of 6.5 (+/-2.9) years. Patients were only mildly impaired with a mean MMSE of 20.9 (+/-4.9) and a mean DRS of 103.1 (+/-12.5) at presentation. Cardiovascular disease was present in 88%, with a mean Hachinski score of 3.4 (+/-2.2). No patient had a history of seizures. Sixty-three percent had depression or depressive symptoms. Neuropsychologically, most patients presented with prominent memory and language deficits and became progressively demented. Neuropathologically, isolated HS was a rare finding; many patients had either very mild or neocortical "plaque only or plaque predominant" Alzheimer's disease (AD) in addition to HS changes. Midfrontal neocortical synaptophysin counts were significantly reduced in all HS patients compared with controls (p = 0.0006). CONCLUSIONS: In the elderly, HS can be a neuropathologic substrate of dementia. Clinically, it can be associated with a course that is difficult to distinguish from AD although cardiac disease and depression are frequent concomitants. Deterioration of cognitive function in these subjects may relate to other pathologic features such as neocortical synapse loss.

E4 allele dosage does not predict cholinergic activity or synapse loss in Alzheimer's disease.

OBJECTIVE: To investigate the relationship between apolipoprotein E (APOE) genotype and both cholinergic dysfunction and synapse loss in AD. BACKGROUND: A reduction in neocortical synapses and marked losses in the cholinergic system occur in AD. It has been suggested that the number of APOE epsilon4 alleles is inversely related to choline acetyltransferase (ChAT) activity, thereby influencing cholinergic function. Whether APOE genotype may influence neocortical synapse loss remains unclear. METHODS: An autopsy series of 182 patients with AD (National Institute on Aging and Consortium to Establish a Registry for Alzheimer's Disease criteria) and 16 normal controls (NC). APOE genotype was determined in blood samples or in postmortem brain tissue. Midfrontal synapse counts (AU/microg) were quantified by a dot-immunobinding assay for synaptophysin (Syn). Midfrontal ChAT activity (nmol/h/100 mg) was assessed using standard assays. RESULTS: Mean midfrontal ChAT activity and Syn were both significantly reduced in patients with AD compared with NC. The relationship between ChAT activity and number of epsilon4 allele copies in AD was complex, with ChAT activity lower in patients with either two or no epsilon4 alleles compared with those with one epsilon4 allele. There was no relationship between APOE genotype and synapse loss in AD. Syn density was almost identical across the three genotypes. CONCLUSIONS: Unlike other studies, we failed to detect a linear relationship between ChAT activity and number of epsilon4 allele copies in the midfrontal cortex of this large sample of patients with AD. Our data also show that the presence of epsilon4 allele does not influence midfrontal synapse loss in AD. This suggests that factors other than APOE genotype may be operative in the decline in midfrontal cholinergic function and synapses seen in AD.