Apolipoprotein E epsilon4 allele increases risk for psychotic symptoms in Alzheimer's disease

Limited awareness of hallucinations in patients with Alzheimer's disease

INTRODUCTION

We investigated the degree of cognitive insight in patients with Alzheimer's Disease (AD) regarding their hallucinations, aiming to elucidate the subjective experiences and perceptions associated with this phenomenon.

METHODS

Using a cross-sectional design, we invited both AD patients (n = 31) and their informants to evaluate the occurrence of hallucinations. Degree of cognitive insight was based upon the discrepancy between the patients' and informants' evaluations.

RESULTS

Analysis demonstrated that AD patients rated the occurrence of hallucinations lower than their informants, indicating that patients tended to underestimate the frequency of their hallucinations. The discrepancy between the ratings of patients and informants was negatively correlated with cognitive functioning, suggesting that a greater discrepancy (indicating poorer insight) was associated with lower cognitive functioning in patients.

DISCUSSION

Our findings highlight the deficits in insight into hallucinations among AD patients, specifically indicating that AD patients have limited awareness of their own hallucinations. Furthermore, our findings support the idea that deficits in insight into hallucinations are associated with the progression of AD.

The neural signatures of psychoses in Alzheimer's disease: a neuroimaging genetics approach

Psychoses in Alzheimer's disease (AD) are associated with worse prognosis. Genetic vulnerability for schizophrenia (SCZ) may drive AD-related psychoses, yet its impact on brain constituents is still unknown. This study aimed to investigate the association between polygenic risk scores (PRSs) for SCZ and psychotic experiences (PE) and grey matter (GM) volume in patients with AD with (AD-PS) and without (AD-NP) psychosis. Clinical, genetic and T1-weighted MRI data for 800 participants were extracted from the ADNI database: 203 healthy controls, 121 AD-PS and 476 AD-NP. PRSs were calculated using a Bayesian approach and analysed at ten p-value thresholds. Standard voxel-based morphometry was used to process MRI data. Logistic regression models including both PRSs for SCZ and PE, and an AD-PRS were used to predict psychosis in AD. Associations between PRSs and GM volume were investigated in the whole sample and the three groups independently. Only the AD-PRS predicted psychosis in AD. Inconsistent associations between the SCZ-PRS and PE-PRS and GM volumes were found across groups. The SCZ-PRS was negatively associated with medio-temporal/subcortical volumes and positively with medial/orbitofrontal volumes in the AD-PS group. Only medio-temporal areas were more atrophic in the AD-PS group, while there was no significant correlation between psychosis severity and GM volume. Although not associated with psychoses, the SCZ-PRS was correlated with smaller medio-temporal and larger orbitofrontal volumes in AD-PS. Similar alterations have also been observed in SCZ patients. This finding suggest a possible disconnection between these regions associated with psychoses in more advanced AD.

Accelerated atrophy in dopaminergic targets and medial temporo-parietal regions precedes the onset of delusions in patients with Alzheimer's disease

People with Alzheimer's disease (AD) and delusions have worse quality of life and prognosis. However, early markers of delusions have not been identified yet. The present study investigated whether there are any detectable differences in grey matter (GM) volume and cognitive changes in the year before symptom onset between patients with AD who did and did not develop delusions. Two matched samples of AD patients, 63 who did (PT-D) and 63 who did not develop delusions (PT-ND) over 1 year, were identified from the Alzheimer's Disease Neuroimaging Initiative database. The Neuropsychiatric Inventory (NPI) was used to assess the presence of delusions. Sixty-three additional matched healthy controls (HC) were selected. Repeated-measures ANCOVA models were used to investigate group-by-time effects on the volume of selected GM regions of interest and on cognitive performance. No neurocognitive differences were observed between patient groups prior to symptom onset. Greater episodic memory decline and GM loss in bilateral caudate nuclei, medio-temporal and midline cingulo-parietal regions were found in the PT-D compared with the PT-ND group. A pattern of faster GM loss in brain areas typically affected by AD and in cortical and subcortical targets of dopaminergic pathways, paralleled by worsening of episodic memory and behavioural symptoms, may explain the emergence of delusions in patients with AD.

The Neuromodulatory Basis of Aggression: Lessons From the Humble Fruit Fly

Aggression is an intrinsic trait that organisms of almost all species, humans included, use to get access to food, shelter, and mating partners. To maximize fitness in the wild, an organism must vary the intensity of aggression toward the same or different stimuli. How much of this variation is genetic and how much is externally induced, is largely unknown but is likely to be a combination of both. Irrespective of the source, one of the principal physiological mechanisms altering the aggression intensity involves neuromodulation. Any change or variation in aggression intensity is most likely governed by a complex interaction of several neuromodulators acting via a meshwork of neural circuits. Resolving aggression-specific neural circuits in a mammalian model has proven challenging due to the highly complex nature of the mammalian brain. In that regard, the fruit fly model Drosophila melanogaster has provided insights into the circuit-driven mechanisms of aggression regulation and its underlying neuromodulatory basis. Despite morphological dissimilarities, the fly brain shares striking similarities with the mammalian brain in genes, neuromodulatory systems, and circuit-organization, making the findings from the fly model extremely valuable for understanding the fundamental circuit logic of human aggression. This review discusses our current understanding of how neuromodulators regulate aggression based on findings from the fruit fly model. We specifically focus on the roles of Serotonin (5-HT), Dopamine (DA), Octopamine (OA), Acetylcholine (ACTH), Sex Peptides (SP), Tachykinin (TK), Neuropeptide F (NPF), and Drosulfakinin (Dsk) in fruit fly male and female aggression.

Long-term antipsychotic use and cognitive decline in community-dwelling older adults with mild-moderate Alzheimer disease: Data from NILVAD

INTRODUCTION

Previous evidence has suggested that antipsychotic use may be associated with accelerated cognitive decline in those living with dementia. However, the cognitive effects of long-term antipsychotic use in community-dwelling older adults with mild-moderate Alzheimer disease (AD) has not been explored to date.

METHODS

We assessed the impact of long-term antipsychotic use on the rate of cognitive decline (Alzheimer's Disease Assessment Scale-Cognitive Subsection) and dementia progression (Clinical Dementia Rating-Sum of Boxes [CDR-Sb]/Disability Assessment for Dementia [DAD]) over 18 months in older adults with mild-moderate AD.

RESULTS

Of 509 participants with mild-moderate AD, one-tenth (54/509; 10.6%) were prescribed an antipsychotic for the 18-month study duration. Antipsychotic use was significantly associated with accelerated cognitive decline at both 12 (β: 3.53, 0.91-6.17, p = 0.008) and 18 months (β: 3.81, 0.49-7.14, p = 0.024) in addition to greater dementia progression at both 12 (β: 1.85, -0.97-2.73, p < 0.001 for CDR-Sb/β: -3.33, -5.56-1.10, p = 0.003 for DAD) and 18 months (β: 1.41, 0.16-2.67, p = 0.027 for CDR-Sb/β: -3.86, -6.64 to -1.08, p = 0.006 for DAD). APOE ε4 carriers experienced significantly greater cognitive decline with long-term antipsychotic use.

CONCLUSIONS

Long-term antipsychotic use was associated with greater cognitive decline and dementia progression in community-dwelling older adults with mild-moderate AD. Our findings are consistent with previous evidence encouraging cautious and careful consideration of risks versus benefits of antipsychotic usage in those with AD.

Apolipoprotein E ϵ4 allele and neuropsychiatric symptoms among older adults in Central Africa (EPIDEMCA study)

OBJECTIVES

To evaluate the association between neuropsychiatric symptoms and apolipoprotein E (APOE) ϵ4 allele among older people in Central African Republic (CAR) and the Republic of Congo (ROC).

DESIGN

Multicenter population-based study following a two-phase design.

SETTING

From 2011 to 2012, rural and urban areas of CAR and ROC.

PARTICIPANTS

People aged 65 and over.

MEASUREMENTS

Following screening using the Community Screening Interview for Dementia, participants with low cognitive scores (CSI-D ≤ 24.5) underwent clinical assessment. Dementia diagnosis followed the DSM-IV criteria and Peterson's criteria were considered for Mild Cognitive Impairment (MCI). Neuropsychiatric symptoms were evaluated through the brief version of the Neuropsychiatric Inventory (NPI-Q). Blood samples were taken from all consenting participants before APOE genotyping was performed by polymerase chain reaction (PCR). Logistic regression models were used to evaluate the association between the APOE ϵ4 allele and neuropsychiatric symptoms.

RESULTS

Overall, 322 participants had complete information on both neuropsychiatric symptoms and APOE status. Median age was 75.0 years and 81.1% were female. Neuropsychiatric symptoms were reported by 192 participants (59.8%) and at least 1 APOE ϵ4 allele was present in 135 (41.9%). APOE ϵ4 allele was not significantly associated with neuropsychiatric symptoms but showed a trend toward a protective effect in some models.

CONCLUSION

This study is the first one investigating the association between APOE ϵ4 and neuropsychiatric symptoms among older people in sub-Saharan Africa (SSA). Preliminary findings indicate that the APOE ϵ4 allele was not associated with neuropsychiatric symptoms. Further research seems, however, needed to investigate the protective trend found in this study.

Prevalence of delusions in drug-naïve Alzheimer disease patients: A meta-analysis

INTRODUCTION

Neuropsychiatric symptoms (NPS) are common at all stages of Alzheimer disease (AD). Delusions in AD are associated with negative clinical consequences and may signal rapid disease progression. Hence, we sought to determine the prevalence of delusions in drug-naïve (no cholinesterase inhibitor or neuroleptic medications) AD patients.

METHODS

In this meta-analysis, a search of the EMBASE, MEDLINE, and PsycINFO databases was performed. We selected studies reporting delusion prevalence measured by the Neuropsychiatric Inventory (NPI) in drug-naïve AD patients. An aggregate delusion event rate with 95% confidence interval (CI) was calculated. The I² statistic was used to assess the magnitude of between-study heterogeneity. Single variable meta-regressions allowed examination of the effect of moderating factors and heterogeneity. Quantitative measures were used to appraise for publication bias.

RESULTS

We identified 6 studies with 591 participants allowing calculation of the aggregate delusional prevalence rate. Irrespective of dementia severity, the aggregate event rate for delusions was 29.1% (95% CI: 20-41%; I²  = 84.59). No publication bias was observed.

CONCLUSION

This meta-analysis calculates a 29.1% prevalence rate of delusions in AD patients. There is a trend towards increasing delusion prevalence in concordance with increasing severity of dementia. Given delusions are associated with poorer outcomes, the obtained prevalence should motivate clinicians to screen carefully for delusions. Current literature limitations warrant future studies, with sub-analyses on dementia severity, and other neurobiological factors known to influence the presence of delusions.

Apolipoprotein E and affective symptoms in mild cognitive impairment and Alzheimer's disease dementia: A systematic review and meta-analysis

OBJECTIVE

APOE status has been associated to affective symptoms in cognitively impaired subjects, with conflicting results.

METHODS

Databases CINAHL, Embase, PsychINFO and PubMed were searched for studies evaluating APOE genotype with affective symptoms in MCI and AD dementia. Symptoms were meta-analyzed separately and possible sources of heterogeneity were examined.

RESULTS

Fifty-three abstracts fulfilled the eligibility criteria. No association was found between the individual symptoms and APOE ε4 carriership or zygosity. For depression and anxiety, only pooled unadjusted estimates showed positive associations with between-study heterogeneity, which could be explained by variation in study design, setting and way of symptom assessment.

CONCLUSIONS

There is no evidence that APOE ε4 carriership or zygosity is associated with the presence of depression, anxiety, apathy, agitation, irritability or sleep disturbances in cognitively impaired subjects. Future research should shift its focus from this single polymorphism to a more integrated view of other biological factors.

Hallucinations in Alzheimer's disease: failure to suppress irrelevant memories

INTRODUCTION

Research with patients with schizophrenia suggests that inhibitory dysfunction leads to the emergence of redundant or irrelevant information from long-term memory into awareness, and that this process may be involved in generating hallucinations. We investigated whether inhibitory dysfunction in Alzheimer's disease (AD) leads to hallucinations.

METHOD

AD participants and healthy matched controls were assessed with a hallucinations scale and a directed forgetting task. On the directed forgetting task, they were asked to retain a list of 10 words (i.e., List 1). Thereafter, half of the participants were asked to forget this list whereas the other half were asked to retain the list in memory. After the List 1 presentation, all participants were asked to retain another list of 10 words and, successively, were asked to remember all of the words from both lists, regardless of the previous forget or remember instruction.

RESULTS

Relative to healthy matched controls, AD participants showed difficulties in suppressing the words from List 1. AD participants also showed more hallucinatory experiences than healthy matched controls. Interestingly, a significant correlation was observed between the score on the hallucinations measure and difficulties in suppressing List 1 in AD participants.

DISCUSSION

Hallucinations in AD may, at least in part, be related to difficulties in suppressing memory representations, such that unwanted or repetitive thoughts intrude into consciousness.

In Thai Nationals, the ApoE4 Allele Affects Multiple Domains of Neuropsychological, Biobehavioral, and Social Functioning Thereby Contributing to Alzheimer's Disorder, while the ApoE3 Allele Protects Against Neuropsychiatric Symptoms and Psychosocial Deficits

The apolipoprotein E epsilon 4 (ApoE4) allele is the strongest genetic risk factor for Alzheimer's disorder (AD) and is associated with semantic and episodic memory deficits. The aim of this study was to examine the associations between ApoE alleles (E2, E3, E4) and genotypes and neuropsychological tests, behavioral functions, and dementia symptoms as assessed using Consortium to Establish a Registry for Alzheimer's Disease (CERAD). This study included 60 patients with Alzheimer's disorder (AD), 60 with mild cognitive disorder (MCI), and 62 normal volunteers. ApoE4 carriers and individuals with E3/E4 and E4/E4 genotypes show an increased incidence of AD, but not MCI. ApoE4 carriers and especially E4/E4 homozygotes show a worse outcome on the CERAD total score, Blessed Dementia Scale, and Short Blessed Test and lower scores on the Verbal Fluency Test, Boston Naming Test, Constructional Praxis Recall, and Word List Memory, Recall, and Recognition. ApoE4 carriers and E4/E3 heterozygotes show higher scores on the Clock Drawing Test. ApoE4 carriers show a worse outcome on the CERAD clinical history scores of memory, language, personality, ADL, orientation, and social skills, while allele AopE3 carriers show better scores on activities of daily living (ADL) and social skills. ApoE3 carriers show lower total weighted, irritability/aggression, and behavioral dysregulation scores on the Behavior Rating Scale for Dementia. The results show that in Thai individuals, the presence of ApoE4 allele is accompanied by a multifarious decline in neurocognitive functions and behavioral features and that ApoE3 may convey protection against neuropsychiatric symptoms and a decline in social skills. ApoE4 and especially the E4/E4 genotype may affect multiple domains of cognitive, biobehavioral, and social functioning thereby contributing to AD phenomenology.

Association Between Psychosis Phenotype and APOE Genotype on the Clinical Profiles of Alzheimer's Disease

BACKGROUND

Psychosis is a common phenomenon in Alzheimer's disease (AD). The APOE ε4 allele is the strongest genetic risk factor for the development of AD, but its association with psychosis remains unclear.

OBJECTIVE

We investigated the associations between psychosis, subdivided into delusions and hallucinations, as well as APOE ε4 allele on cognitive and functional outcomes. Secondarily, we investigated the associations between APOE ε4, Lewy bodies, and psychosis.

METHODS

Data from the National Alzheimer's Coordinating Center (NACC) were used. Nine hundred patients with a confirmed diagnosis of AD based on the NIA-AA Reagan were included in the analysis. Global cognition was assessed using the Mini-Mental State Exam (MMSE) and functional status was assessed using the Functional Activities Questionnaire (FAQ). Psychosis status was determined using the Neuropsychiatric Inventory Questionnaire (NPI-Q). Factorial design was used to assess the effects of psychosis and APOE ε4, as well as their interaction.

RESULTS

Psychosis and the presence of APOE ε4 were both associated with lower MMSE scores, while only psychosis was associated with higher FAQ scores. Furthermore, patients with hallucinations had lower MMSE and higher FAQ scores than patients with only delusions. There was a significant interaction effect between psychosis and APOE ε4 on MMSE scores, with APOE ε4 negatively affecting patients with hallucinations-only psychosis. APOE ε4 was positively associated with the presence of Lewy body pathology, and both were found to be more prevalent in psychotic patients, with a stronger association with hallucinations.

CONCLUSION

Psychosis in AD was associated with greater cognitive and functional impairments. Patients with hallucinations-with or without delusions-conferred even greater deficits compared to patients with only delusions. The APOE ε4 allele was associated with worse cognition, especially for patients with hallucination-only psychosis. APOE ε4 may mediate cognitive impairment in the hallucinations phenotype through the development of Lewy bodies. Our findings support that subtypes of psychosis should be evaluated separately.

Clinical and neurocognitive aspects of hallucinations in Alzheimer's disease

Due to their prevalence, hallucinations are considered as one of the most frequent psychotic symptoms in Alzheimer's disease (AD). These psychotic manifestations reduce patients' well-being, increase the burden of caregivers, contribute to early institutionalization, and are related with the course of cognitive decline in AD. Considering their consequences, we provide a comprehensive account of the current state of knowledge about the prevalence and characteristics of hallucinations in AD. We propose a comprehensive and testable theoretical model about hallucinations in AD: the ALZHA (ALZheimer and HAllucinations) model. In this model, neurological, genetic, cognitive, affective, and iatrogenic factors associated with hallucinations in AD are highlighted. According to the ALZHA model, hallucinations in AD first involve trait markers (i.e., cognitive deficits, neurological deficits, genetic predisposition and/or sensory deficits) to which state markers that may trigger these experiences are added (e.g., psychological distress and/or iatrogenic factors). Finally, we provide recommendations for assessment and management of these psychotic manifestations in AD, with the aim to benefit patients, caregivers, and health professionals.

Cognitive and Functional Correlates of NPI-Q Scores and Symptom Clusters in Mildly Demented Alzheimer Patients

Previous research has demonstrated an association between the emotional and behavioral symptoms of dementia, known as neuropsychiatric symptoms, and cognitive and functional decline among patients with Alzheimer disease (AD). The present study aimed to identify associations between neuropsychiatric symptoms as measured by the Neuropsychiatric Inventory-Questionnaire (NPI-Q) and cognitive and functional performance. Participants were 256 AD patients enrolled in the Alzheimer's Disease and Memory Disorders Center at Baylor College of Medicine. An exploratory factor analysis of the NPI-Q indicated a 2-factor structure consisting of Negative/Oppositional and Anxiety/Restlessness factors. Regression analyses revealed significant associations between greater total severity of neuropsychiatric symptoms and poorer performance on basic and Instrumental Activities of Daily Living. Greater severity of Anxiety/Restlessness symptoms was associated with poor performance on measures of visuospatial functioning and basic and instrumental activities of daily living. The Negative/Oppositional factor was not related to cognition or functioning. In summary, neuropsychiatric symptoms (particularly Anxiety/Restlessness symptoms) were related to cognition and everyday functioning. Proper assessment and treatment of these symptoms is essential for improving cognition and functioning in AD patients.

Hallucinations, loneliness, and social isolation in Alzheimer's disease

INTRODUCTION

Cognitive and functional compromise, as frequently observed in Alzheimer's disease (AD), hinders communication and social interactions. One consequence of this hindrance may be a feeling of loneliness. Moreover, emptiness and boredom, as observed in social isolation and loneliness, may thus be compensated for by creating imagined stimuli. Conditions of loneliness may be viewed as potentially generating hallucinatory experiences. To assess this assumption, the present study explored the relationship between social isolation, loneliness, and hallucinations in a sample of 22 mild AD participants and 24 elderly, healthy controls.

METHODS

Participants were assessed using the Launay-Slade Hallucination Scale, the UCLA Loneliness Scale, and a scale exploring contact with others and social participation.

RESULTS

More hallucinatory experiences, social isolation, and loneliness were found in the AD group than in the healthy control group. Moreover, significant correlations were observed between hallucinations and loneliness and between hallucinations and social isolation in both groups. Finally, hallucinations were predicted by social isolation.

DISCUSSION

Hallucinations may constitute a compensatory mechanism that aims to fulfil communication needs in lonely, elderly participants. Hallucinations may also be regarded as experiences that allow certain participants to escape the cycle of boredom, emptiness, and affective deprivation caused by social isolation.

The Electrophysiological Phenomenon of Alzheimer's Disease: A Psychopathology Theory

The current understanding of Alzheimer's disease (AD) is based on the Aβ and tau pathology and the resulting neuropathological changes, which are associated with manifested clinical symptoms. However, electrophysiological brain changes may provide a more expansive understanding of AD. Hence, the objective of this systematic review is to propose a theory about the electrophysiological phenomenon of Alzheimer's disease (EPAD). The review of literature resulted from an extensive search of PubMed and MEDLINE databases. One-hundred articles were purposively selected. They provided an understanding of the concepts establishing the theory of EPAD (neuropathological changes, neurochemical changes, metabolic changes, and electrophysiological brain changes). Changes in the electrophysiology of the brain are foundational to the association or interaction of the concepts. Building on Berger's Psychophysical Model, it is evident that electrophysiological brain changes occur and affect cortical areas to generate or manifest symptoms from onset and across the stages of AD, which may be prior to pathological changes. Therefore, the interaction of the concepts demonstrates how the psychopathology results from affected electrophysiology of the brain. The theory of the EPAD provides a theoretical foundation for appropriate measurements of AD without dependence on neuropathological changes. Future research is warranted to further test this theory. Ultimately, this theory contributes to existing knowledge because it shows how electrophysiological changes are useful in understanding the risk and progression of AD across the stages.

Behavioral and psychological symptoms in Alzheimer's disease

Neuropsychiatric symptoms (NPS) such as depression, apathy, aggression, and psychosis are now recognized as core features of Alzheimer's disease (AD), and there is a general consensus that greater symptom severity is predictive of faster cognitive decline, loss of independence, and even shorter survival. Whether these symptoms result from the same pathogenic processes responsible for cognitive decline or have unique etiologies independent of AD-associated neurodegeneration is unclear. Many structural and metabolic features of the AD brain are associated with individual neuropsychiatric symptoms or symptom clusters. In addition, many genes have been identified and confirmed that are associated with symptom risk in a few cases. However, there are no single genes strongly predictive of individual neuropsychiatric syndromes, while functional and structural brain changes unique to specific symptoms may reflect variability in progression of the same pathological processes. Unfortunately, treatment success for these psychiatric symptoms may be lower when comorbid with AD, underscoring the importance of future research on their pathobiology and treatment. This review summarizes some of the most salient aspects of NPS pathogenesis.

The APOE ε4 allele is associated with increased frontally mediated neurobehavioral symptoms in amnestic MCI

The apolipoprotein E ε4 allele is a risk factor for late-onset Alzheimer disease (AD), and the frontal lobes may be among the regions that manifest effects of ε4 even early in the disease. We predicted that among patients with amnestic mild cognitive impairment (aMCI) and AD, ε4 would be associated with increased neurobehavioral symptoms when assessed using a measure sensitive to frontal lobe integrity. We obtained cognitive data and caregiver ratings on the Frontal Systems Behavior Scale (FrSBe) for aMCI patients (N=29 ε4 carriers; N=29 noncarriers) and AD patients (N=47 carriers; N=42 noncarriers). In both diagnostic groups, ε4 carriers had lower scores on tests of memory but did not differ on cognitive screening measures or tests of executive functioning. There were no differences in retrospective caregiver ratings of preillness status on the FrSBe by ε4 status in either diagnostic group. However, in the aMCI group, ε4 carriers had elevated current FrSBe Executive Dysfunction scores in comparison with noncarriers. In the AD group, there were no differences in current FrSBe scores by genotype group. Results indicate that ε4-related behavior change occurs in the aMCI stage but may not be apparent by the AD stage.

Apolipoprotein E polymorphism and behavioral and psychological symptoms of dementia in patients with Alzheimer disease

The aims of this study were to identify subsyndromes of behavioral and psychological symptoms of dementia (BPSD) in Alzheimer disease (AD), and to investigate whether the apolipoprotein E (ApoE) gene confers a risk of distinct BPSD subsyndromes. BPSD of 96 patients with AD were assessed using the Neuropsychiatric Inventory. Factor analysis with principal component analysis and varimax rotation was used to construct the BPSD subsyndromes. ApoE genotypes were determined using the TaqMan technology. The results showed that the 5 subsyndromes can be determined, including: agitation/aggression-delusion, euphoria-disinhibition, depression-apathy, hallucination-nighttime behavior, and appetite. ApoE ε4 carriers had higher factor scores in the agitation/aggression-delusion subsyndrome. We demonstrated that ApoE ε4 confers a higher risk for the subsyndrome of agitation/aggression delusion in AD.

PRND 3'UTR polymorphism may be associated with behavioral disturbances in Alzheimer disease

The etiology of behavioral and psychological symptoms of dementia (BPSD) is complex, including putative biological, psychological, social and environmental factors. Recent years have witnessed accumulation of data on the association between genetic factors and behavioral abnormalities in Alzheimer disease (AD). In this research paper, our aim is to evaluate the association between the APOE, CYP46, PRNP and PRND genes and the profile of neuropsychiatric symptoms in Polish subjects with AD and mild cognitive impairment (MCI). We studied 99 patients with AD and 48 subjects with MCI. The presence and profile of BPSD were evaluated at baseline and prospectively with the Neuropsychiatric Inventory (NPI). Patients were dichotomized into those having ever experienced a particular symptom and those who did not over the whole disease period. Genotyping was performed using previously described standard protocols. The prevalence of comorbid behavioral symptoms and the overall level of behavioral burden were significantly greater in AD compared with the MCI group. In AD patients, carrier status of the T allele of the 3'UTR (untranslated region) PRND polymorphism was associated with an increased cumulative behavioral load and an elevated risk for delusions, anxiety, agitation/aggression, apathy and irritability/emotional ability. Among MCI subjects, APOE ε4 carriers demonstrated a reduced risk for nighttime behavior change. No other statistically significant genotype-phenotype correlations were observed, including the APOE, CYP46 and PRNP genes. A precise estimation of the exact significance of particular polymorphisms in BPSD etiology requires future studies on large populations.

Missense substitutions associated with behavioural disturbances in Alzheimer's disease (AD)

Behavioural and psychological symptoms in dementia, or BPSD, occur in the majority of Alzheimer's disease (AD) patients. They are associated with considerable patient morbidity and greater care-giver stress. There is some evidence suggesting that BPSD have a genetic component and a large number of studies have examined the association of candidate genes with these symptoms. This review provides a comprehensive summary of all the published studies investigating the association of candidate gene missense substitutions with BPSD. Missense substitutions could potentially alter protein function or render the protein non-functional, resulting in phenotypic consequences. More than 80 studies investigating the association of 8 missense substitutions in 7 genes with BPSD were identified. However, results of these studies are contradictory and do not provide firm support for these associations. Larger studies and more systematic approaches will delineate the association of missense substitutions with behavioural symptoms in AD.

Saitohin and APOE polymorphisms influence cognition and function in persons with advanced Alzheimer Disease

BACKGROUND/AIMS

Alzheimer disease (AD) is characterized by variability in the onset and progression of cognitive, functional and behavioral symptoms. The purpose of this study was to identify genetic correlates of symptom variability in persons with moderate-to-advanced AD.

METHODS

Repeated measures of cognition, function and behavior were collected from institutionalized persons with AD over 12 months. Candidate genes were assayed.

RESULTS

Single polymorphisms within the saitohin and APOE genes were associated with increased cognitive impairment and functional dependence. The APOE-ε4 allele was associated with increased baseline physical agitation.

CONCLUSION

The development of predictive profiles for the clinical symptoms of AD may increase our ability to identify clinical subgroups for more targeted intervention.

Apolipoprotein E genotypes and neuropsychiatric symptoms and syndromes in late-onset Alzheimer's disease

Neuropsychiatric symptoms (NPS) in dementia, previously denominated as behavioural and psychological symptoms of dementia, are often more distressing, impairing, and costly than cognitive symptoms, representing a major health burden for older adults. These symptoms are common features of Alzheimer's disease (AD), and are one of the major risk factors for institutionalization. There is a high prevalence of neuropsychiatric disturbances in patients with AD, including depression, anxiety, apathy, psychosis, aggression, and agitation. At present, the role of the apolipoprotein E (APOE) genotypes in the development of NPS or neuropsychiatric syndromes/endophenotypes in AD patients is unclear. In this article, we summarized the findings of the studies of NPS and neuropsychiatric syndromes in AD in relation to APOE genotypes, with special attention to the possible underlying mechanisms. While some studies failed to find a significant association between the APOE polymorphism and NPS in late-onset AD, other studies reported a significant association between the APOE ɛ4 allele and an increase in agitation/aggression, hallucinations, delusions, and late-life depression or anxiety. However, current cumulative evidence coming from the few existing longitudinal studies shows no association of APOE genotypes with NPS as a whole in AD. Some negative studies that focused on the distribution of APOE genotypes between AD patients with or without NPS further emphasized the importance of sub-grouping NPS in distinct neuropsychiatric syndromes. Explanations for the variable findings in the existing studies included differences in patient populations, differences in the assessment of neuropsychiatric symptomatology, possible lack of statistical power to detect associations in the negative studies, and small sample sizes generating false positives that cannot be consistently replicated. Finally, many reviewed studies were cross-sectional, whereas it would be of paramount importance to evaluate the risk for incident NPS in relation to the APOE genotype in prospectively followed cohorts of AD patients. In fact, identifying predisposing genetic risk factors may allow us to understand the pathophysiological features of neuropsychiatric syndromes or symptoms in AD, so optimizing possible therapeutic options.

Neuropsychiatric Symptoms, Endophenotypes, and Syndromes in Late-Onset Alzheimer's Disease: Focus on APOE Gene

Neuropsychiatric symptoms, previously denominated as behavioural and psychological symptoms of dementia, are common features of Alzheimer's disease (AD) and are one of the major risk factors for institutionalization. At present, the role of the apolipoprotein E (APOE) gene in the development of neuropsychiatric symptoms in AD patients is unclear. In this paper, we summarized the findings of the studies of neuropsychiatric symptoms and neuropsychiatric syndromes/endophenotypes in AD in relation to APOE genotypes, with special attention to the possible underlying mechanisms. While some studies failed to find a significant association between APOE and neuropsychiatric symptoms in late-onset AD, other studies reported a significant association between the APOE ε4 allele and an increase in agitation/aggression, hallucinations, delusions, and late-life depression or anxiety. Furthermore, some negative studies that focused on the distribution of APOE genotypes between AD patients with or without neuropsychiatric symptoms further emphasized the importance of subgrouping neuropsychiatric symptoms in distinct neuropsychiatric syndromes. Explanations for the variable findings in the existing studies included differences in patient populations, differences in the assessment of neuropsychiatric symptomatology, and possible lack of statistical power to detect associations in the negative studies.

Behavioural genetics of Alzheimer's disease: a comprehensive review

Behavioural and psychological symptoms of dementia (BPSD) are present in the course of the illness in up to 90% of patients with Alzheimer's disease (AD). They are the main source of caregiver burden and one of the major factors contributing to early institutionalization. The involvement of a genetic component in BPSD aetiology seems beyond controversy, though the exact significance of particular polymorphisms is uncertain in the majority of cases. Multiple genes have been assessed for their putative influence on BPSD risk. In this paper we review the behavioural genetics of AD, particularly the importance, with respect to BPSD risk, of genes coding for apolipoprotein E and proteins involved in the process of neurotransmission: serotonin receptors, serotonin transporter, COMT, MAO-A, tryptophan hydroxylase and dopamine receptors. A general conclusion is the striking inconsistency of the findings, unsurprising in the field of psychiatric genetics. The potential reasons for such discrepancy are exhaustively discussed.

Brain derived neurotrophic factor Val66Met polymorphism and psychotic symptoms in Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative disorder with a high prevalence. Since behavioral disturbances, such as psychotic symptoms, represent a key feature of AD, genes related to dopamine, serotonin and brain derived neurotrophic factor (BDNF), are considered as candidate genes for AD. BDNF is a neurotrophin that regulates neurodevelopment, neuroplasticity, and neuronal functions. BDNF is involved in the etiopathogenesis of psychiatric and neurodegenerative disorders. A single base pair polymorphism (BDNF Val66Met) was reported to be associated with AD and/or schizophrenia, as well as other psychoses, although some studies failed to replicate these findings. The aim of the study was to evaluate the association between BDNF Val66Met variants and AD, as well as onset of AD or presence of psychotic symptoms in AD.

METHOD

BDNF Val66Met was analyzed in 211 patients with AD and in 402 aged healthy control subjects. All subjects were ethnically homogenous Caucasians from Croatia, and were subdivided according to the gender, onset of AD, and presence of psychotic symptoms. A χ(2) test, with Bonferroni correction and standardized residuals were used to evaluate the data.

RESULTS

Distribution of the BDNF Val66Met genotypes differed significantly between male and female AD patients with or without psychotic symptoms. This difference was due to the significant contribution of the Met/Val genotype and the combined Met/Met and Met/Val genotypes between psychotic and non-psychotic symptoms in male, but not in female patients with AD. The frequency of the gene variants of the BDNF Val66Met did not differ significantly among male and female patients with AD and control subjects, or between male and female patients with early or late onset AD. There were significant sex related differences in age, duration of illness and scores of dementia between patients with AD.

CONCLUSION

Our male patients were younger, had shorter duration of illness, and had less severe dementia and higher cognitive performance than female AD patients. The gene variants of the BDNF Val66Met polymorphism were significantly associated with the presence of psychotic symptoms in male, but not in female patients with AD. The results had adequate statistical power to suggest that BDNF Val66Met was not related to susceptibility to AD or the onset of AD, but that presence of one or two Met alleles of BDNF Val66Met polymorphism might present a risk factor for psychosis in AD.

Psychotic symptoms in a population-based sample of 85-year-old individuals with dementia

Psychotic symptoms are common in elderly persons with dementia. These symptoms affect a person's ability to function in daily life and put strain on the caregiver. Most studies focus on psychotic symptoms in clinical samples with Alzheimer disease (AD). Thus, their prevalence and relation with dementia subtype and severity in very old populations is unclear. We assessed a representative sample of 85-year-old individuals living in Gothenburg, Sweden (n = 494) using neuropsychiatric examinations, key informant interviews, and medical record reviews; 147 had dementia. Dementia and its severity were diagnosed in accordance with Diagnostic and Statistical Manual of Mental Disorders (Third Edition, Revision [DSM-III-R]) criteria. Alzheimer disease according to the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria was diagnosed in 64 persons and vascular dementia (VaD) according to Erkinjuntti criteria was observed in 69. Fourteen had dementia due to other causes. Psychotic symptoms were classified according to DSM-III-R. The prevalence of psychotic symptoms in this very old population was 36% among AD cases compared to 54% in VaD cases (P = .04). Proportions with psychotic symptoms increased with increasing dementia severity in individuals with AD. No such association could be shown in those with VaD. This finding of a high proportion of psychotic symptoms also in individuals with mild severity of VaD should alert health professionals to evaluate dementia in very old patients who present with hallucinations or delusions.

Glutamatergic model psychoses: prediction error, learning, and inference

Modulating glutamatergic neurotransmission induces alterations in conscious experience that mimic the symptoms of early psychotic illness. We review studies that use intravenous administration of ketamine, focusing on interindividual variability in the profundity of the ketamine experience. We will consider this individual variability within a hypothetical model of brain and cognitive function centered upon learning and inference. Within this model, the brains, neural systems, and even single neurons specify expectations about their inputs and responding to violations of those expectations with new learning that renders future inputs more predictable. We argue that ketamine temporarily deranges this ability by perturbing both the ways in which prior expectations are specified and the ways in which expectancy violations are signaled. We suggest that the former effect is predominantly mediated by NMDA blockade and the latter by augmented and inappropriate feedforward glutamatergic signaling. We suggest that the observed interindividual variability emerges from individual differences in neural circuits that normally underpin the learning and inference processes described. The exact source for that variability is uncertain, although it is likely to arise not only from genetic variation but also from subjects' previous experiences and prior learning. Furthermore, we argue that chronic, unlike acute, NMDA blockade alters the specification of expectancies more profoundly and permanently. Scrutinizing individual differences in the effects of acute and chronic ketamine administration in the context of the Bayesian brain model may generate new insights about the symptoms of psychosis; their underlying cognitive processes and neurocircuitry.

BDNF variants, premorbid educational attainment, and disease characteristics in Alzheimer's disease: an exploratory study

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that promotes neuronal survival, growth, and differentiation. The role of BDNF in learning and memory suggests that it may also modulate the clinical course of Alzheimer's disease (AD). This study aimed to determine whether BDNF genetic variants are related to premorbid educational attainment, progression of cognitive and functional decline, and associated neuropsychiatric symptoms in AD patients. A sample of AD subjects (N = 341) was genotyped for the BDNF polymorphisms: Val66Met, C270T, and G-712A. Subjects received tests of cognition and daily function at baseline and at multiple subsequent time points. They were also characterized for the frequency and severity of neuropsychiatric symptoms. There was a significant effect of Val66Met genotype on educational attainment (F = 7.49, df = 2,329, P = 0.00066), with Met/Met homozygotes having significantly lower education than both the Val/Met and Val/Val groups. No association was observed between any BDNF polymorphism and measures of cognitive or functional decline. The T-allele of the C270T polymorphism was associated with a higher prevalence of neuropsychiatric symptoms and specifically with the presence of hallucinations. The effect of the Val66Met polymorphism on premorbid educational attainment is intriguing and should be verified in a larger sample.

Genetics of psychosis in Alzheimer's disease: a review

In and of itself, late-onset Alzheimer's disease (AD) can be a devastating illness. However, a sub-group of AD patients develop psychosis as the disease progresses. These patients have an added burden of greater cognitive impairment, higher rates of institutionalization, and higher mortality than AD patients without psychosis. While the etiopathogenesis such as psychosis in AD (AD+P) is not known, mounting evidence accrued over the past ten years indicates that AD+P represents a distinct phenotype with a genetic basis. Elucidating the genetic mechanism of AD+P is crucial if better pharmaceutical treatments are to be developed for these patients. The goal of this review is to summarize what is currently known regarding the genetic basis of psychosis in AD. Specific attention is given to familial aggregation and heritability, linkage to chromosomal loci, and associations of candidate genes of APOE and the monoamine neurotransmitter system.

Prominent neuroleptic sensitivity in a case of early-onset Alzheimer disease due to presenilin-1 G206A mutation

OBJECTIVE

We describe atypical motor and cognitive features in a case of familial Alzheimer disease (FAD) due to presenilin-1 (PS-1) mutation.

BACKGROUND

Extrapyramidal signs (EPS) typically are a late-presenting feature of sporadic Alzheimer disease (AD), but relatively little data are available regarding EPS in FAD.

METHOD

A 59-year-old, right-handed man of Caribbean-Hispanic descent underwent brain imaging studies, laboratory tests for AD, and serial neurologic and neuropsychologic evaluations.

RESULTS

The patient presented with recent-onset delusional ideation associated with cognitive decline. Prominent EPS developed soon after initiation of an atypical neuroleptic agent. Neuropsychologic evaluation revealed global cognitive deficits; he was found to be a carrier of a PS-1 point mutation at position G206A. EPS resolved completely after discontinuing the neuroleptic agent and coincided with improved motor speed, set initiation, and verbal fluency.

CONCLUSIONS

Severe neuroleptic sensitivity and associated deficits of cognitive speed occurred in response to a dopaminergic antagonist agent; both responded readily to withdrawal of the offending agent. Patients with PS-1 AD may be at substantially increased risk of neuroleptic-induced EPS. That feature underscores the heterogeneity of the FAD clinical phenotype.