Familial influence on variation in age of onset and behavioural phenotype in Alzheimer's disease

Alzheimer's Disease-Related Psychosis: An Overview of Clinical Manifestations, Pathogenesis, and Current Treatment

Behavioral and psychotic manifestations, including aggression, delusions, and hallucinations, are frequent comorbidities in patients with debilitating nervous illnesses such as Alzheimer's disease (AD), Amyotrophic Lateral Sclerosis, Multiple Sclerosis, and Parkinson's disease. AD-related psychosis may be linked to a poor disease prognosis, highlighting that early detection and management are mandatory. The manifestations are variable and may be very heterogeneous, imposing a real diagnostic issue. Some assessment tools such as BEHAVE-AD, CERAD-BRSD, and the Psycho-Sensory Hallucinations Scale have been designed to facilitate the diagnosis. The mechanisms behind neurodegeneration-related psychosis are complex and are not fully understood, imposing a burden on researchers to find appropriate management modalities. Familial history and some genetic disturbances may have a determinant role in these delusions and hallucinations in cases with AD. The loss of neuronal cells, atrophy in some regions of the central nervous, and synaptic dysfunction may also contribute to these comorbidities. Furthermore, inflammatory disturbances triggered by pro-inflammatory agents such as interleukins and tumor necrosis factors are stratified among the potential risk factors of the onset of numerous psychotic symptoms in Alzheimer's patients. Little is known about the possible management tools; therefore, it is urgent to conduct well-designed trials to investigate pharmacological and non-pharmacological interventions that can improve the care process of these patients. This review summarizes the current findings regarding the AD-related psychosis symptoms, pathological features, assessment, and management.

Variants regulating ZBTB4 are associated with age-at-onset of Alzheimer's disease

The identification of novel genetic modifiers of age-at-onset (AAO) of Alzheimer's disease (AD) could advance our understanding of AD and provide novel therapeutic targets. A previous genome scan for modifiers of AAO among families affected by early-onset AD caused by the PSEN2 N141I variant identified 2 loci with significant evidence for linkage: 1q23.3 and 17p13.2. Here, we describe the fine-mapping of these 2 linkage regions, and test for replication in 6 independent datasets. By fine-mapping these linkage signals in a single large family, we reduced the linkage regions to 11% their original size and nominated 54 candidate variants. Among the 11 variants associated with AAO of AD in a larger sample of Germans from Russia, the strongest evidence implicated promoter variants influencing NCSTN on 1q23.3 and ZBTB4 on 17p13.2. The association between ZBTB4 and AAO of AD was replicated by multiple variants in independent, trans-ethnic datasets. Our results show association between AAO of AD and both ZBTB4 and NCSTN. ZBTB4 is a transcriptional repressor that regulates the cell cycle, including the apoptotic response to amyloid beta, while NCSTN is part of the gamma secretase complex, known to influence amyloid beta production. These genes therefore suggest important roles for amyloid beta and cell cycle pathways in AAO of AD.

Genetics of psychosis of Alzheimer disease

Psychotic symptoms, comprised of delusions and hallucinations, occur in about half of individuals with Alzheimer disease (AD with psychosis, AD+P). These individuals have greater agitation, aggression, depression, functional impairment, and mortality than individuals without psychosis (AD-P). Although the exact etiopathogenesis of AD+P is unclear, the rapidly developing field of genomics continues to expand our understanding of this disease. Several independent studies have demonstrated familial aggregation and heritability of AD+P. Linkage studies have been suggestive of loci on several chromosomes associated with AD+P. Association studies examining apolipoprotein E gene, the best established genetic risk factor for late-onset AD, did not find any significant association of this gene with AD+P. Other candidate gene studies focusing on monoamine neurotransmitter systems have yielded equivocal results. A genome-wide association study and studies examining copy number variations recently have detected suggestive associations, but have been underpowered. Approaches to increase sizes of AD+P samples for genome wide association studies are discussed. © 2016 Wiley Periodicals, Inc.

Association between DCHS2 gene and mild cognitive impairment and Alzheimer's disease in an elderly Brazilian sample

OBJECTIVES

In 2012, Kamboh and colleagues published a genome-wide association study that identified the DCHS2 gene (rs1466662 T/A) influencing the age at onset of Alzheimer's disease (AD). We aimed to investigate if there is association between the DCHS2 gene and amnestic mild cognitive impairment (aMCI) and AD in a sample of the Brazilian population.

METHODS

143 controls, 79 aMCI and 299 AD patients were selected and submitted to the same protocol of tests. Genotyping was performed using the Real Time PCR RESULTS: Amnestic MCI patients showed a higher prevalence of AA than controls and a lower frequency of TT when compared with controls. We also stratified the sample according to the APOE ε4 status. No difference in DCHS2 genotype or allelic frequency occurred in the APOE ε4 allele carrier subgroup. Amnestic MCI patients showed a higher frequency of AA genotype and a lower frequency of TA and TT when compared with controls in APOE ε4 allele non-carrier subgroup. The allelic distribution followed the same pattern. In AD group, we observed a significant difference with a higher A allelic frequency in AD in this subgroup. A multiple logistic regression demonstrated that in APOE ε4 non-carriers, allele rs1466662 was associated to aMCI group. Different variables were associated with aMCI and AD according to APOE ε4 status in our sample. Low level of education was associated with AD, while diabetes mellitus type 2 was associated with aMCI. Copyright © 2016 John Wiley & Sons, Ltd.

CONCLUSIONS

Our findings suggest a possible role for DCHS2 gene in aMCI and AD.

Genetics of Psychosis in Alzheimer Disease

Psychosis occurs in approximately half of patients with Alzheimer disease (AD with psychosis, AD+P). AD+P patients have more rapid cognitive decline, greater behavioral symptoms, and higher mortality than do AD patients without psychosis. Studies in three independent cohorts have shown that psychosis in AD aggregates in families, with estimated heritability of 29.5 - 60.8%. These findings have motivated studies to investigate and uncover the genes responsible for the development of psychosis, with the ultimate goal of identifying potential biologic mechanisms that may serve as leads to specific therapies. Linkage analyses have implicated loci on chromosomes 2, 6, 7, 8, 15, and 21 with AD+P. Association studies of APOE do not support it as a risk gene for psychosis in AD. No other candidate genes, such as neurodegenerative and monoamine genes, show conclusive evidence of association with AD+P. However, a recent genome-side association study has produced some promising leads, including among them genes that have been associated with schizophrenia. This review summarizes the current knowledge of the genetic basis of AD+P.

Understanding delusion in dementia: a review

Alzheimer's disease and other dementia are associated with cognitive and functional impairment, as well as neuropsychiatric sequelae, including psychotic features. Research has largely concentrated on the study of cognitive decline, but the associated behavioral and neuropsychiatric symptoms are of equal importance in the clinical profile of the disease. Delusions are common, disabling and persistent in the course of dementia. The purpose of the present review was to examine the phenomenon of delusion in people with dementia. We searched the electronic databases for original research and review articles using the search terms "delusion, dementia, Alzheimer's disease, frontotemporal dementia, vascular dementia and Lewy body disease". Various types of explanations have been proposed regarding the etiology of delusional belief in dementia, and cerebral correlates are considered. Pharmacological and non-pharmacological treatments are analyzed.

Genome scan in familial late-onset Alzheimer's disease: a locus on chromosome 6 contributes to age-at-onset

Alzheimer's disease (AD) is a common, genetically complex, fatal neurodegenerative disorder of late life. Although several genes are known to play a role in early-onset AD, identification of the genetic basis of late onset AD (LOAD) has been challenging, with only the APOE gene known to have a high contribution to both AD risk and age-at-onset. Here, we present the first genome-scan analysis of the complete, well-characterized University of Washington LOAD sample of 119 pedigrees, using age-at-onset as the trait of interest. The analysis approach used allows for a multilocus trait model while at the same time accommodating age censoring, effects of APOE as a known genetic covariate, and full pedigree and marker information. The results provide strong evidence for linkage of loci contributing to age-at-onset to genomic regions on chromosome 6q16.3, and to 19q13.42 in the region of the APOE locus. There was evidence for interaction between APOE and the locus on chromosome 6q and suggestive evidence for linkage to chromosomes 11p13, 15q12-14, and 19p13.12. These results provide the first independent confirmation of an AD age-at-onset locus on chromosome 6 and suggest that further efforts towards identifying the underlying causal locus or loci are warranted.

Catechol-O-methyltransferase genetic variant associated with the risk of Alzheimer's disease in a Brazilian population

The aim of the present study was to examine the association between polymorphism in the catechol-O-methyltransferase(COMT) gene and Alzheimer's disease (AD) in a Brazilian population. The case-control method was used to study the association between AD and genetic variants of COMT. Six tag single-nucleotide polymorphisms(SNPs) in the COMT gene were genotyped by RT-PCR. Our findings showed that the 6 tag SNPs analyzed in this study were not associated with AD at the allele and genotype levels in comparison with the control group. No statistical difference was found between groups with and without behavioral and psychological symptoms of dementia (BPSD). Our results do not support the hypothesis that the polymorphisms of the COMT gene may be associated with susceptibility to AD with and without BPSD.

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.

Neurobiology of delusions in Alzheimer's disease

Alzheimer's disease (AD) is associated with cognitive and functional impairment as well as neuropsychiatric sequelae, including psychotic symptoms such as delusions and hallucinations. Strong evidence supports the need to study delusions separate from hallucinations. Integrating the epidemiology, clinical correlates, and neuropathological and genetic literature for delusions in AD allows us to speculate on etiology and mechanisms. Plaque and tangle deposition in individuals with susceptible alleles of serotonergic, muscarinic, nicotinic, or Apoε4 genes appears to result in disruption of cortical circuitry, culminating in delusions. While delusions in AD correspond to a phenotype distinct from AD without delusions, subtypes of delusions may also define further distinct clinical entities. Persecutory delusions may occur earlier in the illness and have a more significant genetic component than misidentification delusions, which are associated with increased cognitive impairment and advanced dementia. Clearly distinguishing between these two syndromes is essential to making progress in the area of delusions in AD.

Evidence for three loci modifying age-at-onset of Alzheimer's disease in early-onset PSEN2 families

Families with early-onset Alzheimer's disease (AD) sharing a single PSEN2 mutation exhibit a wide range of age-at-onset, suggesting that modifier loci segregate within these families. While APOE is known to be an age-at-onset modifier, it does not explain all of this variation. We performed a genome scan within nine such families for loci influencing age-at-onset, while simultaneously controlling for variation in the primary PSEN2 mutation (N141I) and APOE. We found significant evidence of linkage between age-at-onset and chromosome 1q23.3 (P < 0.001) when analysis included all families, and to chromosomes 1q23.3 (P < 0.001), 17p13.2 (P = 0.0002), 7q33 (P = 0.017), and 11p14.2 (P = 0.017) in a single large pedigree. Simultaneous analysis of these four chromosomes maintained strong evidence of linkage to chromosomes 1q23.3 and 17p13.2 when all families were analyzed, and to chromosomes 1q23.3, 7q33, and 17p13.2 within the same single pedigree. Inclusion of major gene covariates proved essential to detect these linkage signals, as all linkage signals dissipated when PSEN2 and APOE were excluded from the model. The four chromosomal regions with evidence of linkage all coincide with previous linkage signals, associated SNPs, and/or candidate genes identified in independent AD study populations. This study establishes several candidate regions for further analysis and is consistent with an oligogenic model of AD risk and age-at-onset. More generally, this study also demonstrates the value of searching for modifier loci in existing datasets previously used to identify primary causal variants for complex disease traits.

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.

Assessment and familial aggregation of psychosis in Alzheimer's disease from the National Institute on Aging Late Onset Alzheimer's Disease Family Study

Determining the genetic architecture of late onset Alzheimer's disease remains an important research objective. One approach to the identification of novel genetic variants contributing to the disease is the classification of biologically meaningful subgroups within the larger late-onset Alzheimer's disease phenotype. The occurrence of psychotic symptoms in patients with late-onset Alzheimer's disease may identify one such group. We attempted to establish methods for the reliable assessment of psychotic symptoms in a large, geographically dispersed collection of families, multiply affected with late onset Alzheimer's disease, who were participants in the larger National Institute on Aging Late Onset Alzheimer's Disease Family Study; and to characterize the correlates and familial aggregation of psychosis within this cohort. We found that reliable assessments of psychotic symptoms during in-person or phone interviews were readily implemented. The presence of psychosis in late onset Alzheimer's disease was significantly associated with degree of cognitive impairment, and significantly, albeit modestly, correlated with the severity of other behavioural symptoms. Psychosis significantly aggregated within late onset Alzheimer's disease families suggesting that it may identify a genetically determined subgroup. Future studies should examine the linkage and association of psychosis with genetic variation within these families.

Investigation of dopamine receptors in susceptibility to behavioural and psychological symptoms in Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) patients commonly suffer from behavioural and psychological symptoms of dementia (BPSD). A genetic component to the development of BPSD in AD has been supported. Polymorphisms within dopamine receptors DRD1, DRD2, DRD3 and DRD4 have previously been investigated in a few interesting studies that are reviewed here and extended using our patient cohort.

METHODS

Our large cohort of 395 probable AD patients had longitudinal information on the BPSD (Neuropsychiatric Inventory), which was used to dichotomise patients into whether they had ever suffered from a given symptom within the study period, or not. These measures were related to the DRD1 (A-48G), DRD2 (ser311cys; C-ins/del), DRD3 (ser9gly) and DRD4 (VNTR) genotype and allele frequencies.

RESULTS

Associations were revealed between DRD3 and elation, and between DRD4 with agitation/aggression and with depression; however, these findings do not remain significant after correction for multiple testing. No associations were found with the other genetic variants and these symptoms and no associations were observed between any of the polymorphic variants examined and delusions, hallucinations, psychosis and aberrant motor behaviour.

CONCLUSION

Our data, in combination with a review of the literature, reveal a potential role for the VNTR variant of DRD4 in the development of depression in AD patients. The findings presented here need to be replicated in large, well characterised longitudinal cohorts.

Prediction of psychosis onset in Alzheimer disease: the role of depression symptom severity and the HTR2A T102C polymorphism

Psychotic symptoms in Alzheimer disease (AD + P) identify a heritable phenotype associated with a more severe course. We recently found an association of AD + P with depression symptom severity. Reports have shown an association of a serotonin-2A receptor (HTR2A) gene T102C polymorphism with AD + P and with depression during AD. We examined the interaction of this common genetic polymorphism with depression and increased psychosis risk. Subjects with possible or probable AD or mild cognitive impairment (MCI) without psychosis at study entry were genotyped for the HTR2A T102C polymorphism and reassessed every 6 months until psychosis onset. Psychotic and depressive symptoms were rated using the CERAD behavioral rating scale (CBRS). Cox proportional hazard models with time-dependent covariates were used to examine associations with psychosis onset. A total of 324 Caucasian subjects completed at least one follow-up exam. Depressive symptom severity was a strong predictor of psychosis onset. Neither psychosis onset nor depression severity was associated with the HTR2A genotype. Genotype interacted with depression severity to moderate the risk of AD + P onset. This did not result from an interaction of HTR2A genotype with antidepressant use. Psychosis onset in AD is strongly associated with severity of depressive symptoms, an association that may be modified by HTR2A genotype.

Role of serotonin transporter polymorphisms in the behavioural and psychological symptoms in probable Alzheimer disease patients

BACKGROUND/AIMS

Alzheimer disease (AD) patients commonly suffer from behavioural and psychological symptoms of dementia (BPSD). A genetic component to BPSD development in AD has been demonstrated. This is an investigation of whether the linked polymorphic region and variable number tandem repeat variants of the serotonin transporter (SERT) are associated with BPSD.

METHODS

The longitudinal measures of BPSD of our large cohort of 367 AD patients were assessed by the Neuropsychiatric Inventory. Measures with good evidence of serotonergic involvement (delusions, hallucinations, depression, anxiety, agitation/aggression and irritability) were related to genotype and allele frequencies of the linked polymorphic region and variable number tandem repeat variants.

RESULTS

Analysis revealed significant relationships between the linked polymorphic region variant long allele with irritability and the variable number tandem repeat 10-repeat allele with psychosis, but no associations were found with depression, anxiety or agitation/aggression.

CONCLUSION

Our data and review of previous studies suggest SERT could play a minor role in development of psychosis and aggressive/irritable tendencies; however, further investigations are required in large, well-characterized cohorts.

Age-at-onset linkage analysis in Caribbean Hispanics with familial late-onset Alzheimer's disease

The aim of the study was to identify chromosomal regions that may harbor putative genetic variants influencing age at onset in familial late-onset Alzheimer's disease (LOAD). Data from a genome-wide scan that included genotyping of APOE were analyzed in 1,161 individuals from 209 families of Caribbean Hispanic ancestry with a mean age at onset of 73.3 years multiply affected by LOAD. Two-point and multipoint analyses were conducted using variance component methods using 376 microsatellite markers with an average intermarker distance of 9.3 cM. Family-based test of association was also conducted for the same set of markers. Age at onset of symptoms among affected individuals was used as the quantitative trait. Our results showed that the presence of APOE-epsilon4 lowered the age at onset by 3 years. Several candidate loci were identified. Using linkage analysis strategy, the highest logarithm of odds (LOD) scores were obtained using a conservative definition of LOAD at 5q15 (LOD = 3.1), 17q25.1 (LOD = 2.94), 14q32.12 (LOD = 2.36), and 7q36.3 (LOD = 2.29) in a model that adjusted for APOE-epsilon4 and other covariates. Both linkage and family-based association identified 17p13 as a candidate region. Family-based association analysis showed markers at 12q13 (p = 0.00002), 13q33 (p = 0.00043), and 14q23 (p = 0.00046) to be significantly associated with age at onset. The current study supports the hypothesis that there are additional genetic loci that could influence age at onset of late onset Alzheimer's disease. The novel loci at 5q15, 17q25.1, 13q33, and 17p13 and the previously reported loci at 7q36.3, 12q13, 14q23, and 14q32 need further investigation.

Genetic determination in onset age of wrist fracture

The onset age of fracture may be useful to explore the clinical and genetic heterogeneity of fracture study. In the present study, we investigated the heritability of the onset age of wrist fracture (OAWF) in 30 female full-sib pairs. The phenotypic correlation coefficient of OAWF was 0.309 (P=0.09) for this cohort of female sib pairs, and the narrow-sense heritability (h2) was estimated to be 0.618 (P=0.09). In addition, the h2 derived from the variance component model implemented in SOLAR was 0.722 (P<0.05). This study, for the very first time, suggested that OAWF is under genetic control and thus potentially helps clarify genetic heterogeneity of wrist fracture.

Premorbid personality and behavioral and psychological symptoms in probable Alzheimer disease

OBJECTIVES

Previous research investigating the influence of premorbid personality on behavioral and psychological symptoms in dementia (BPSD) has produced mixed findings. Addressing some limitations of previous studies, the authors aimed to investigate whether some of the common individual symptoms of BPSD (depression, anxiety, irritability, and aggression) were associated with key aspects of previous personality (neuroticism and agreeableness); and also to perform an exploratory investigation into the broader influence of personality factors on behavioral and psychological syndromes.

METHODS

Two hundred eight patients with a diagnosis of probable Alzheimer disease were assessed for the presence of BPSD over the disease course using the caregiver-rated Neuropsychiatric Inventory (NPI). One or two knowledgeable informants rated patients' midlife personalities using a retrospective version of the NEO-FFI questionnaire.

RESULTS

Premorbid neuroticism was correlated with anxiety and total NPI score, although not with depression. Premorbid agreeableness was negatively correlated with agitation and irritability. Principal components analysis of the 10 NPI behavioral domains identified three syndromes: "agitation/apathy," "psychosis," and "affect." In stepwise linear regression analyses, including personality domains from the Five-Factor Model and a range of potential confounders as independent variables; the only significant personality predictor of a behavioral syndrome was "agitation/apathy," predicted by lower premorbid agreeableness.

CONCLUSION

Lower premorbid agreeableness is associated with agitation and irritability symptoms in Alzheimer disease and also predicts an "agitation/apathy" syndrome. The relationship between premorbid neuroticism and BPSD is less straightforward, and premorbid neuroticism does not appear to be associated with depression in Alzheimer disease or predict an "affect" syndrome.

The effect of the apolipoprotein E gene polymorphisms and haplotypes on behavioural and psychological symptoms in probable Alzheimer's disease

BACKGROUND

Patients with Alzheimer's disease and dementia commonly suffer from behavioural and psychological symptoms of dementia (BPSD). A genetic component to BPSD development in Alzheimer's disease has been demonstrated. Several studies have investigated whether the exon 4 epsilon2/epsilon3/epsilon4 haplotype of the apolipoprotein E (APOE) gene is associated with BPSD, with variable results.

OBJECTIVE

We investigated the exon 4 polymorphisms and extended this study to include promoter polymorphisms and the resultant haplotypes across the gene.

METHODS

Our large independent cohort of 388 patients with longitudinal measures of BPSD assessed by the Neuropsychiatric Inventory was used to analyse whether any of these variants were associated with the presence of BPSD.

RESULTS

We revealed several significant relationships before correction for multiple testing. The exon 4 haplotype was associated with hallucinations and anxiety, A-491T with irritability, T-427C with agitation/aggression and appetite disturbances, and T-219C with depression. Haplotype analyses of all variants did not reveal any statistically significant findings.

CONCLUSIONS

Our data and a review of previous studies showed a diversity of relationships, suggesting that these findings might be due to chance and so collectively do not support a role for the APOE gene in BPSD.

Role of 5HT 2A and 5HT 2C polymorphisms in behavioural and psychological symptoms of Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) patients suffer from behavioural and psychological symptoms of dementia (BPSD). A genetic component to BPSD development in AD has been demonstrated. Polymorphisms within serotonin receptors 5HT(2A) and 5HT(2C) have been previously investigated in a few interesting studies reviewed here, however, their role remains unclear.

METHODS

Our large cohort of 394 patients had longitudinal information on the BPSD (Neuropsychiatric Inventory), which was used to dichotomise patients into whether they had ever suffered from a given symptom within the study period and give each patient a severity score. These measures were related to the 5HT(2A) T102C and 5HT(2C) cys23ser genotype and allele frequencies.

RESULTS

Our data supports previous reports of an increased frequency of the C allele and CC genotype of the T102C variant of 5HT(2A) with hallucinations, delusions, psychosis and aberrant motor behaviour, however, we dispute previous associations with depression and aggression. We describe for the first time an increase in the C allele and CC genotype frequencies of the cys23ser variant of 5HT(2C) with anxiety and support previous associations with appetite disturbances in females.

CONCLUSION

This review and extension of previous data presents support for the role of 5HT(2A) and 5HT(2C) in the development of certain symptoms, although the effect size may be small.

Genetics and dementia nosology

In preparation for the development of the Diagnostic and Statistical Manual of Mental Disorders (5th ed), the American Psychiatric Association convened workshops reviewing scientific evidence relevant to diagnosis of dementia. One of the domains covered was genetics, which is reviewed here. The following areas are reviewed: genetic data on Alzheimer's disease and other dementias; the impact of nosology on genetic research in terms of its potential to improve diagnostic sensitivity and specificity and to decrease heterogeneity; the impact of genetic research findings on nosology, specific diagnostic criteria, and subtypes; and recommendations and future directions. The focus is on Alzheimer's disease, where more genetic data are available, and other dementias are reviewed more briefly. In addition, a separate section reviews the relationship of genetic findings and mild cognitive impairment, a boundary zone between normal aging and dementia, particularly Alzheimer's disease.

The NEO-FFI is a reliable measure of premorbid personality in patients with probable Alzheimer's disease

AIM

To assess the inter-informant reliability, intra-informant reliability and internal consistency of the NEO-FFI as a measure of premorbid personality in patients with Alzheimer's Disease (AD).

SUBJECTS

One hundred and five persons with NINCDS-ADRDA probable AD for the assessment of inter-informant reliability and internal consistency, and 30 for the assessment of intra-informant reliability.

METHODS

Premorbid personality was rated retrospectively by close relatives remembering the patient as he/she had been when aged in his/her forties. One hundred and five AD patients were rated by two separate informants. Thirty AD patients were rated by the same informant on separate occasions one year apart.

RESULTS

Inter-informant reliability for the five domain scores of the NEO-FFI was shown to range from fair to good when measured using the single measure Intraclass Correlation Co-efficient (ICC) (0.52-0.64), and to range from good to excellent when measured using the average ICC (0.68-0.78). Intra-informant reliability for four out of the five domains was shown to be excellent when measured using the single ICC (0.81-0.92), and good for the remaining domain (0.72). Intra-informant reliability was found to be excellent for all five domains when measured using the average ICC (0.84-0.96). Internal consistency of the five domains was good.

CONCLUSIONS

The NEO-FFI can be used reliably to measure premorbid personality in patients with probable AD. It may be useful to maximise reliability by using a mean domain score based on questionnaires completed by two or more informants who knew the patient well earlier in life.

Behavioural and psychological signs and symptoms of dementia across cultures: current status and the future

BACKGROUND

Behavioural and psychological symptoms of dementia (BPSD) have been poorly studied in developing countries, in ethnic minority groups in a given country and in cross-national studies.

METHODS

The literature on BPSD from developing countries, ethnic minority groups in a given country and cross-national studies was examined.

RESULTS

There is emerging literature on BPSD from the settings was studied. These studies provide useful preliminary data on the prevalence and correlates of BPSD. Moreover, the data illustrate possible cross-cultural differences in BPSD and their correlates. A number of instruments measuring either individual BPSD within a BPSD domain, measuring features of a BPSD domain or features of a range of BPSD domains have been developed in languages other than English for use in developing countries and ethnic minority groups in a given country.

CONCLUSIONS

There is a need for methodologically similar and uniform studies of BPSD across countries and ethnic groups in a given country using appropriately validated instruments. It is suggested that a consensus should be reached by researchers on the best instrument(s) to be developed in languages other than English for use in these settings and, in turn, these instruments should be developed using appropriate methodology. This could allow identification of the genetic and environmental aetiology of BPSD and the influence of gene-environment interaction.

Alzheimer disease subjects with psychosis have increased schizotypal symptoms before dementia onset

BACKGROUND

Recent findings have demonstrated the familiality of psychotic symptoms occurring during Alzheimer disease (AD with psychosis, AD+P), particularly for subjects with multiple psychotic symptoms. We have proposed a model in which genes that confer a small risk for psychosis interact with neurodegenerative illness to yield manifest psychotic symptoms during AD. One prediction of this model would be that AD+P subjects would have evidence of increased degrees of subsyndromal psychosis before AD onset.

METHODS

We used the psychosis (positive symptoms) and psychotic personality disorder sections (paranoid, schizoid, and schizotypal) of the Family Interview for Genetic Studies (FIGS) to interview the primary caregivers of AD subjects. Caregivers were specifically instructed to answer questions with regard to the subject's behavior before AD onset. Interviewers were blind to presence of psychosis during AD. Subjects were grouped by whether they had at least one or had multiple psychotic symptoms during AD.

RESULTS

Scores on the FIGS subscales were generally low, reflecting a low frequency of endorsement of psychotic symptoms before AD. There was a trend for the schizotypal scores to be elevated in the AD+P group, which was highly significant in the AD+P group with multiple psychotic symptoms. There was no significant association of paranoid or schizoid scores with either group.

CONCLUSIONS

Although limited by small sample size and retrospective design, these data are novel in that they indicate an association of subsyndromal psychotic symptoms before AD onset with psychosis in AD. Subsyndromal psychosis might be useful for classifying AD+P families for genetic mapping studies. Prospective confirmation is required.

Genome screen for loci influencing age at onset and rate of decline in late onset Alzheimer's disease

We performed an affected sib-pair (ASP) linkage analysis to test for the effects of age at onset (AAO), rate of decline (ROD), and Apolipoprotein E (APOE) genotype on linkage to late-onset Alzheimer's disease (AD) in a sample comprising 428 sib-pairs. We observed linkage of mean AAO to chromosome 21 in the whole sample (max LOD = 2.57). This came entirely from the NIMH sample (max LOD = 3.62), and was strongest in pairs with high mean AAO (>80). A similar effect was observed on chromosome 2q in the NIMH sample (max LOD = 2.73); this region was not typed in the IADC/UK sample. Suggestive evidence was observed in the combined sample of linkage of AAO difference to chromosome 19q (max LOD = 2.33) in the vicinity of APOE and 12p (max LOD = 2.22), with linkage strongest in sib-pairs with similar AAO. Mean ROD showed suggestive evidence of linkage to chromosome 9q in the whole sample (max LOD = 2.29), with the effect strongest in the NIMH sample (max LOD = 3.58), and in pairs with high mean ROD. Additional suggestive evidence was also observed in the NIMH sample with AAO difference on chromosome 6p (max LOD = 2.44) and 15p (max LOD = 1.87), with linkage strongest in pairs with similar AAO, and in the UK sample with mean ROD on chromosome 1p (max LOD = 2.73, linkage strongest in pairs with high mean ROD). We also observed suggestive evidence of increased identical by descent (IBD) in APOE epsilon4 homozygotes on chromosome 1 (max LOD = 3.08) and chromosome 9 (max LOD = 3.34). The previously reported genome-wide linkage of AD to chromosome 10 was not influenced by any of the covariates studied.

A review of the evidence from family, twin and adoption studies for a genetic contribution to adult psychiatric disorders

Family, twin and adoption studies have provided major evidence for the role of genetics in numerous psychiatric disorders including obsessive-compulsive disorder, panic disorder, major depressive disorder, bipolar disorder, schizophrenia and Alzheimer's disease. As the search for patterns of inheritance and candidate genes of these complex disorders continues, we review relevant findings from quantitative genetic studies and outline the main challenges for the field of psychiatric genetics to focus on in order to more definitively establish the underpinnings of genetic and environmental influences of adult psychopathology.

Evidence for a novel late-onset Alzheimer disease locus on chromosome 19p13.2

Late-onset familial Alzheimer disease (LOFAD) is a genetically heterogeneous and complex disease for which only one locus, APOE, has been definitively identified. Difficulties in identifying additional loci are likely to stem from inadequate linkage analysis methods. Nonparametric methods suffer from low power because of limited use of the data, and traditional parametric methods suffer from limitations in the complexity of the genetic model that can be feasibly used in analysis. Alternative methods that have recently been developed include Bayesian Markov chain-Monte Carlo methods. These methods allow multipoint linkage analysis under oligogenic trait models in pedigrees of arbitrary size; at the same time, they allow for inclusion of covariates in the analysis. We applied this approach to an analysis of LOFAD on five chromosomes with previous reports of linkage. We identified strong evidence of a second LOFAD gene on chromosome 19p13.2, which is distinct from APOE on 19q. We also obtained weak evidence of linkage to chromosome 10 at the same location as a previous report of linkage but found no evidence for linkage of LOFAD age-at-onset loci to chromosomes 9, 12, or 21.

Molecular genetics of Alzheimer's disease

Alzheimer disease (AD) is the most common cause of dementia. In the past decade, many advances in the understanding of the etiology of AD have been reported. Familial early onset AD is a heterogeneous disorder that can be caused by mutations in at least three different genes. Current studies are focused on identifying genetic risk factors for late onset AD. In this article, the authors will review the progress in understanding the pathogenic implications of the genes mutated in familial early onset AD and the mapping studies to identify additional genes involved in late-onset AD.

Association between interleukin 1-beta promoter (-511) polymorphism and depressive symptoms in Alzheimer's disease

Depressive symptoms have been associated with raised interleukin 1-beta (IL-1beta) plasma levels. The presence of behavioral and psychological symptoms of dementia (BPSD) in Alzheimer's disease, including depressive symptoms, have been shown to be influenced by common genetic polymorphisms. A common polymorphism in the promoter region of IL-1beta has been linked to altered synthesis of IL-1beta. We hypothesize that this common genetic polymorphism is a risk factor for the appearance of depressive symptoms in AD. A total of 133 subjects, diagnosed as probable AD and 156 controls were genotyped for the -511 variant of IL-1beta. Neither genotype or allele frequencies differed between the AD and control group. However, an allelic association was found between the T variant and the symptoms of depression in AD subjects. Genotypic analysis showed that heterozygotes were three times more likely to develop depressive symptoms than CC homozygotes.

Psychotic symptoms in Alzheimer disease: evidence for a distinct phenotype

Though efforts to identify the genetic etiology of Alzheimer disease (AD) have made substantial progress, to date only some of the genes contributing to AD risk have been identified. Utilization of more etiologically homogeneous subphenotypes represents one strategy to facilitate the identification of novel risk genes in complex disorders. In this review, we evaluate the hypothesis that psychotic symptoms, such as delusions and hallucinations, define a suitable subphenotype in AD patients for gene-mapping efforts. Psychotic symptoms occur in 40-60% of patients with AD and are associated with more severe cognitive deficits and a more rapidly deteriorating course. The presence of psychotic symptoms in AD confers increased risk of similar symptoms to affected siblings. Candidate gene association analyses and initial linkage analysis have yielded significant results. We discuss possible genetic models of psychotic symptoms in AD, and suggest strategies for further investigation. Identification of such genetic factors may facilitate gene-mapping studies for both AD and idiopathic psychoses.

Genotype and phenotype in Alzheimer's disease

BACKGROUND

Patients with Alzheimer's disease show a wide variation in clinical phenotype. Genetic research has been largely concerned with the role of mutations or common variants as risk factors for the disease. Do genetic factors also influence clinical phenotype?

AIMS

To examine the evidence that genetic factors influence the clinical expression of the disease in addition to influencing risk.

METHOD

A selective review was made of the key literature.

RESULTS

Mutations in three genes, coding for amyloid precursor protein, presenilin-1 and presenilin-2, and a common variation (epsilon4) in another gene, APOE, have been shown to lead to an earlier development of the disease. More recently, genetic association and twin studies have suggested a role for genetic factors in the development of other aspects of clinical phenotype, notably the appearance of non-cognitive symptoms.

CONCLUSIONS

In Alzheimer's disease genetic variation influences a number of aspects of clinical phenotype.

The clinical phenotype of familial and sporadic late onset Alzheimer's disease

BACKGROUND

Familial factors are clearly associated with an increased risk of developing late onset Alzheimer's disease (LOAD). However, there is emerging evidence to suggest that familial factors may also influence clinical phenotype. To date, most studies have focussed on familial influences upon age of onset or duration of illness and few studies have compared the frequency of non-cognitive symptoms between familial and sporadic LOAD.

OBJECTIVE

To describe the clinical phenotype, with an emphasis on non-cognitive symptoms, of patients with LOAD and to explore familial differences.

METHOD

374 patients with LOAD were recruited from the community based Camberwell Dementia Case Register and a comparison made of the clinical phenotype of patients with and without a first degree family history of dementia.

RESULTS

A first degree family history of dementia was found in 27% of fully ascertained cases. An earlier age of onset was found in familial cases (77.2 years compared to 78.3 years, p<0.05). However, no other differences in clinical phenotype, including the rate of cognitive decline, duration or the frequency of non-cognitive symptoms, were found between familial and sporadic cases.

CONCLUSIONS

Apart from an earlier age of onset, patients with familial LOAD, as a group, do not have major differences in their clinical phenotype compared to patients with sporadic LOAD.