Dementia and mild cognitive impairment in adults with intellectual disability: issues of diagnosis

A new model to understand the complexity of inequalities in dementia

Many people living with dementia and unpaid carers experience inequalities in care related to challenges in receiving a correct diagnosis, care and support. Whilst complexities of the evidence are well recognised including barriers in receiving a diagnosis or post-diagnostic care, no coherent model has captured the far-reaching types and levels of inequalities to date. Building on the established Dahlgren & Whitehead Rainbow model of health determinants, this paper introduces the new Dementia Inequalities model. The Dementia Inequalities model, similar to the original general rainbow model, categorises determinants of health and well-being in dementia into three layers: (1) Individual; (2) Social and community networks; and (3) Society and infrastructure. Each layer comprises of general determinants, which have been identified in the original model but also may be different in dementia, such as age (specifically referring to young- versus late-onset dementia) and ethnicity, as well as new dementia-specific determinants, such as rare dementia subtype, having an unpaid carer, and knowledge about dementia in the health and social care workforce. Each layer and its individual determinants are discussed referring to existing research and evidence syntheses in the field, arguing for the need of this new model. A total of 48 people with lived, caring, and professional experiences of dementia have been consulted in the process of the development of this model. The Dementia Inequalities model provides a coherent, evidence-based overview of inequalities in dementia diagnosis and care and can be used in health and social care, as well as in commissioning of care services, to support people living with dementia and their unpaid carers better and try and create more equity in diagnosis and care.

Symptoms and age of prodromal Alzheimer's disease in Down syndrome: a systematic review and meta-analysis

The diagnostic criteria for adult-onset Alzheimer's disease (AD) in patients with Down syndrome (DS) have not been standardised. This study investigated the specific symptoms of AD in the prodromal stage of DS, the mean age at diagnosis at each stage of dementia, and the relationship between intellectual disability (ID) and dementia. PubMed, Web of Science, and Embase were searched for studies on DS, AD, early-stage disease, initial symptoms, and prodromal dementia registered between January 2012 and January 2022. We also performed a meta-analysis of the differences between the mean age at prodromal symptoms and AD diagnosis and the proportion of mild cognitive impairment in patients with mild and moderately abnormal ID. We selected 14 articles reporting the behavioural and psychological symptoms of dementia (BPSD) and memory- and language-related impairments as early symptoms of AD in patients with DS. The specific symptoms of BPSD were classified into five categories: irritability (agitation), apathy, abnormal behaviour, adaptive functioning, and sleep disturbance. The mean age at the diagnosis of prodromal symptoms and AD dementia was 52.7 and 56.2 years, respectively (mean difference, + 3.11 years; 95% CI 1.82-4.40) in the meta-analysis. The diagnosis of mild dementia tended to correlate with ID severity (odds ratio [OR], 1.38; 95% CI 0.87-2.18). The features of behaviour-variant frontotemporal dementia may be clinically confirmed in diagnosing early symptoms of DS-associated AD (DSAD). Moreover, age-appropriate cognitive assessment is important. Further studies are required to evaluate DSAD using a combination of biomarkers and ID-related data.

Exploring the lived experiences and care challenges of formal paid caregivers for people with intellectual disability and dementia

A greater number of people with intellectual disability are living into older age and are at increased risk of developing conditions such as dementia. Caring for a person with dementia presents several challenges for formal caregivers due to the progressive nature of the disease. An interpretive phenomenological analysis was used to understand the lived experiences of a purposive sample of formal caregivers in caring for people with intellectual disability and dementia. Discussions from 14 individual interviews generated data were analysed. Four key super-ordinate themes emerged which were: (1) recognising early indicators and diagnosis, (2) post diagnostic support, (3) coping with change and (4) need for future development. Themes reflected the experiences, barriers to dementia diagnosis and provide a valuable insight into the challenges faced by formal caregivers in providing aged care services.

Early Chronic Fluoxetine Treatment of Ts65Dn Mice Rescues Synaptic Vesicular Deficits and Prevents Aberrant Proteomic Alterations

Down syndrome (DS) is the most common form of inherited intellectual disability caused by trisomy of chromosome 21, presenting with intellectual impairment, craniofacial abnormalities, cardiac defects, and gastrointestinal disorders. The Ts65Dn mouse model replicates many abnormalities of DS. We hypothesized that investigation of the cerebral cortex of fluoxetine-treated trisomic mice may provide proteomic signatures that identify therapeutic targets for DS. Subcellular fractionation of synaptosomes from cerebral cortices of age- and brain-area-matched samples from fluoxetine-treated vs. water-treated trisomic and euploid male mice were subjected to HPLC-tandem mass spectrometry. Analysis of the data revealed enrichment of trisomic risk genes that participate in regulation of synaptic vesicular traffic, pre-synaptic and post-synaptic development, and mitochondrial energy pathways during early brain development. Proteomic analysis of trisomic synaptic fractions revealed significant downregulation of proteins involved in synaptic vesicular traffic, including vesicular endocytosis (CLTA, CLTB, CLTC), synaptic assembly and maturation (EXOC1, EXOC3, EXOC8), anterograde axonal transport (EXOC1), neurotransmitter transport to PSD (SACM1L), endosomal-lysosomal acidification (ROGDI, DMXL2), and synaptic signaling (NRXN1, HIP1, ITSN1, YWHAG). Additionally, trisomic proteomes revealed upregulation of several trafficking proteins, involved in vesicular exocytosis (Rab5B), synapse elimination (UBE3A), scission of endocytosis (DBN1), transport of ER in dendritic spines (MYO5A), presynaptic activity-dependent bulk endocytosis (FMR1), and NMDA receptor activity (GRIN2A). Chronic fluoxetine treatment of Ts65Dn mice rescued synaptic vesicular abnormalities and prevented abnormal proteomic changes in adult Ts65Dn mice, pointing to therapeutic targets for potential treatment of DS.

Neurofilament light chain concentration mediates the association between regional medial temporal lobe structure and memory in adults with Down syndrome

INTRODUCTION

Virtually all people with Down syndrome (DS) develop neuropathology associated with Alzheimer's disease (AD). Atrophy of the hippocampus and entorhinal cortex (EC), as well as elevated plasma concentrations of neurofilament light chain (NfL) protein, are markers of neurodegeneration associated with late-onset AD. We hypothesized that hippocampus and EC gray matter loss and increased plasma NfL concentrations are associated with memory in adults with DS.

METHODS

T1-weighted structural magnetic resonance imaging (MRI) data were collected from 101 participants with DS. Hippocampus and EC volume, as well as EC subregional cortical thickness, were derived. In a subset of participants, plasma NfL concentrations and modified Cued Recall Test scores were obtained. Partial correlation and mediation were used to test relationships between medial temporal lobe (MTL) atrophy, plasma NfL, and episodic memory.

RESULTS

Hippocampus volume, left anterolateral EC (alEC) thickness, and plasma NfL were correlated with each other and were associated with memory. Plasma NfL mediated the relationship between left alEC thickness and memory as well as hippocampus volume and memory.

DISCUSSION

The relationship between MTL gray matter and memory is mediated by plasma NfL levels, suggesting a link between neurodegenerative processes underlying axonal injury and frank gray matter loss in key structures supporting episodic memory in people with DS.

Parental Survey on Spanish‑English Bilingualism in Neurotypical Development and Neurodevelopmental Disabilities in the United States

Objectives

The cognitive and social benefits of bilingualism for children, including those with neurodevelopmental disabilities (NDDs), have been documented. The present study was designed to characterize and compare English and Spanish use in Hispanic families with and without NDDs residing in the U.S. as well as to understand parental perceptions of their child's bilingualism and of community and professional support.

Methods

We conducted an online survey of 84 Spanish-speaking parents of 4- to 24-year-olds with (n = 44) and without NDDs (n = 40) who were born in and living in the U.S.

Results

We found that bilingualism was a desired goal for 95% of our families. We also found, however, that 17.1% of parents of children with NDDs have raised them as monolinguals English-speakers, as they thought there were reasons for that, while all families from the NT group raised their children in both languages. In addition, nearly 40% of the NDD children only speak English, compared to a 5% in the NT group. Finally, parents of children with NDDs cite a lack of support for bilingualism in the community (47.6% do not feel supported, compared to a 7.9% in the NT group) and recommendation from professionals as major factors for not raising their children as bilingual.

Conclusions

The results suggest a need to educate professionals from many disciplines about the benefits of bilingualism for children with NDDs and for implementation of inclusion policies that provide access to dual-language programs.

Toward the Identification of Neurophysiological Biomarkers for Alzheimer's Disease in Down Syndrome: A Potential Role for Cross-Frequency Phase-Amplitude Coupling Analysis

Cross-frequency coupling (CFC) mechanisms play a central role in brain activity. Pathophysiological mechanisms leading to many brain disorders, such as Alzheimer's disease (AD), may produce unique patterns of brain activity detectable by electroencephalography (EEG). Identifying biomarkers for AD diagnosis is also an ambition among research teams working in Down syndrome (DS), given the increased susceptibility of people with DS to develop early-onset AD (DS-AD). Here, we review accumulating evidence that altered theta-gamma phase-amplitude coupling (PAC) may be one of the earliest EEG signatures of AD, and therefore may serve as an adjuvant tool for detecting cognitive decline in DS-AD. We suggest that this field of research could potentially provide clues to the biophysical mechanisms underlying cognitive dysfunction in DS-AD and generate opportunities for identifying EEG-based biomarkers with diagnostic and prognostic utility in DS-AD.

The Global Deterioration Scale for Down Syndrome Population (GDS-DS): A Rating Scale to Assess the Progression of Alzheimer's Disease

The aim of this study is to adapt and validate the global deterioration scale (GDS) for the systematic tracking of Alzheimer's disease (AD) progression in a population with Down syndrome (DS). A retrospective dual-center cohort study was conducted with 83 participants with DS (46.65 ± 5.08 years) who formed the primary diagnosis (PD) group: cognitive stability (n = 48), mild cognitive impairment (n = 24), and Alzheimer's disease (n = 11). The proposed scale for adults with DS (GDS-DS) comprises six stages, from cognitive and/or behavioral stability to advanced AD. Two neuropsychologists placed the participants of the PD group in each stage of the GDS-DS according to cognitive, behavioral and daily living skills data. Inter-rater reliability in staging with the GDS-DS was excellent (ICC = 0.86; CI: 0.80-0.93), and the agreement with the diagnosis categories of the PD group ranged from substantial to excellent with κ values of 0.82 (95% CI: 0.73-0.92) and 0.85 (95% CI: 0.72, 0.99). Performance with regard to the CAMCOG-DS total score and orientation subtest of the Barcelona test for intellectual disability showed a slight progressive decline across all the GDS-DS stages. The GDS-DS scale is a sensitive tool for staging the progression of AD in the DS population, with special relevance in daily clinical practice.

The Pictorial Screening Memory Test (P-MIS) for Adults with Moderate Intellectual Disability and Alzheimer's Disease

In this study, we examined normative data and diagnostic accuracy of a pictorial screening test to detect memory impairment for mild cognitive impairment (MCI) and Alzheimer's disease (AD) in Spanish-speaking adults with intellectual disability (ID). A total of 94 volunteers with ID (60 controls, 17 MCI, and 17 AD), were evaluated by neuropsychological tests including the PMIS-ID in a cross-sectional validation study. Discriminative validity between the MCI, AD, and control group was analyzed by the area under the ROC curve. A cut-off score of 4.5 on the immediate recall trial had a sensitivity of 69% and a specificity of 80% to detect memory impairment (AUC = 0.685; 95% CI = 0.506-0.863) in the AD group. The PMIS-ID is a useful screening test to rule out a diagnosis of memory decline in people with moderate level of ID and AD, and it shows good psychometric properties.

Joint-label fusion brain atlases for dementia research in Down syndrome

Research suggests a link between Alzheimer's Disease in Down Syndrome (DS) and the overproduction of amyloid plaques. Using Positron Emission Tomography (PET) we can assess the in-vivo regional amyloid load using several available ligands. To measure amyloid distributions in specific brain regions, a brain atlas is used. A popular method of creating a brain atlas is to segment a participant's structural Magnetic Resonance Imaging (MRI) scan. Acquiring an MRI is often challenging in intellectually-imparied populations because of contraindications or data exclusion due to significant motion artifacts or incomplete sequences related to general discomfort. When an MRI cannot be acquired, it is typically replaced with a standardized brain atlas derived from neurotypical populations (i.e. healthy individuals without DS) which may be inappropriate for use in DS. In this project, we create a series of disease and diagnosis-specific (cognitively stable (CS-DS), mild cognitive impairment (MCI-DS), and dementia (DEM-DS)) probabilistic group atlases of participants with DS and evaluate their accuracy of quantifying regional amyloid load compared to the individually-based MRI segmentations. Further, we compare the diagnostic-specific atlases with a probabilistic atlas constructed from similar-aged cognitively-stable neurotypical participants. We hypothesized that regional PET signals will best match the individually-based MRI segmentations by using DS group atlases that aligns with a participant's disorder and disease status (e.g. DS and MCI-DS). Our results vary by brain region but generally show that using a disorder-specific atlas in DS better matches the individually-based MRI segmentations than using an atlas constructed from cognitively-stable neurotypical participants. We found no additional benefit of using diagnose-specific atlases matching disease status. All atlases are made publicly available for the research community.

Highlight

Down syndrome (DS) joint-label-fusion atlases provide accurate positron emission tomography (PET) amyloid measurements.A disorder-specific DS atlas is better than a neurotypical atlas for PET quantification.It is not necessary to use a disease-state-specific atlas for quantification in aged DS.Dorsal striatum results vary, possibly due to this region and dementia progression.

Building the Future Therapies for Down Syndrome: The Third International Conference of the T21 Research Society

Research focused on Down syndrome has increased in the last several years to advance understanding of the consequences of trisomy 21 (T21) on molecular and cellular processes and, ultimately, on individuals with Down syndrome. The Trisomy 21 Research Society (T21RS) is the premier scientific organization for researchers and clinicians studying Down syndrome. The Third International Conference of T21RS, held June 6-9, 2019, in Barcelona, Spain, brought together 429 scientists, families, and industry representatives to share the latest discoveries on underlying cellular and molecular mechanisms of T21, define cognitive and behavioral challenges and better understand comorbidities associated with Down syndrome, including Alzheimer's disease and leukemia. Presentation of cutting-edge results in neuroscience, neurology, model systems, psychology, cancer, biomarkers and molecular and phar-ma-cological therapeutic approaches demonstrate the compelling interest and continuing advancement in all aspects of understanding and ameliorating conditions associated with T21.

The neglected puzzle of dementia in people with severe/profound intellectual disabilities: A systematic literature review of observable symptoms

BACKGROUND

Dementia is increasingly prevalent in people with severe/profound intellectual disabilities. However, early detection and diagnosis of dementia is complex in this population. This study aimed to identify observable dementia symptoms in adults with severe/profound intellectual disabilities in available literature.

METHOD

A systematic literature search was conducted in PubMed, PsycINFO and Web of Science with an exhaustive search string using a combination of search terms for severe/profound intellectual disabilities and dementia/ageing.

RESULTS

Eleven studies met inclusion criteria. Cognitive decline, behavioural and psychological alterations, decline in activities of daily living as well as neurological and physical changes were found.

CONCLUSIONS

Only a very limited number of studies reported symptoms ascribed to dementia in adults with severe/profound intellectual disabilities. Given the complexity of signalling and diagnosing dementia, dedicated studies are required to unravel the natural history of dementia in this population.

Hypersynchronized Magnetoencephalography Brain Networks in Patients with Mild Cognitive Impairment and Alzheimer's Disease in Down Syndrome

Introduction: The majority of individuals with Down syndrome (DS) show signs of Alzheimer's disease (AD) neuropathology in their fourth decade. However, there is a lack of specific markers for characterizing the disease stages while considering this population's differential features. Methods: Forty-one DS individuals participated in the study, and were classified into three groups according to their clinical status: Alzheimer's disease (AD-DS), mild cognitive impairment (MCI-DS), and controls (CN-DS). We performed an exhaustive neuropsychological evaluation and assessed brain functional connectivity (FC) from magnetoencephalographic recordings. Results: Compared with CN-DS, both MCI-DS and AD-DS showed a pattern of increased FC within the high alpha band. The neuropsychological assessment showed a generalized cognitive impairment, especially affecting mnestic functions, in MCI-DS and, more pronouncedly, in AD-DS. Discussion: These findings might help to characterize the AD-continuum in DS. In addition, they support the role of the excitatory/inhibitory imbalance as a key pathophysiological factor in AD. Impact statement The pattern of functional connectivity (FC) hypersynchronization found in this study resembles the largely reported Alzheimer's disease (AD) FC evolution pattern in population with typical development. This study supports the hypothesis of the excitatory/inhibitory imbalance as a key pathophysiological factor in AD, and its conclusions could help in the characterization and prediction of Down syndrome individuals with a greater likelihood of converting to dementia.

Evaluation of the National Task Group-Early Detection Screen for Dementia: Sensitivity to 'mild cognitive impairment' in adults with Down syndrome

BACKGROUND

The accuracy of the National Task Group-Early Detection Screen for Dementia (NTG-EDSD) was evaluated in a sample of 185 adults with Down syndrome (DS), emphasizing 'mild cognitive impairment (MCI-DS)'.

METHOD

Knowledgeable informants were interviewed with the NTG-EDSD, and findings were compared to an independent dementia status rating based on consensus review of detailed assessments of cognition, functional abilities and health status (including physician examination).

RESULTS

Results indicated that sections of the NTG-EDSD were sensitive to MCI-DS, with one or more concerns within the 'Memory' or 'Language and Communication' domains being most informative.

CONCLUSIONS

The NTG-EDSD is a useful tool for evaluating dementia status, including MCI-DS. However, estimates of sensitivity and specificity, even for detecting frank dementia, indicated that NTG-EDSD findings need to be supplemented by additional sources of relevant information to achieve an acceptable level of diagnostic/screening accuracy.

Longitudinal assessment of dementia measures in Down syndrome

INTRODUCTION

Early detection of dementia symptoms is critical in Down syndrome (DS) but complicated by clinical assessment barriers. The current study aimed to characterize cognitive and behavioral impairment using longitudinal trajectories comparing several measures of cognitive and behavioral functioning.

METHODS

Measures included global cognitive status (Severe Impairment Battery [SIB]), motor praxis (Brief Praxis Test [BPT]), and clinical dementia informant ratings (Dementia Questionnaire for People with Learning Disabilities [DLD]). One-year reliability was assessed using a two-way mixed effect, consistency, single measurement intraclass correlation among non-demented participants. Longitudinal assessment of SIB, BPT, and DLD was completed using linear mixed effect models.

RESULTS

One-year reliability (n = 52; 21 male) was moderate for DLD (0.69 to 0.75) and good for SIB (0.87) and BPT (0.80). Longitudinal analysis (n = 72) revealed significant age by diagnosis interactions for SIB (F(2, 115.02) = 6.06, P = .003), BPT (F(2, 85.59) = 4.56, P = .013), and DLD (F(2, 103.56) = 4.48, P = .014). SIB progression (PR) had a faster decline in performance versus no-dementia (ND) (t(159) = -2.87; P = .013). Dementia had a faster decline in BPT performance versus ND (t(112) = -2.46; P = .041). PR showed quickly progressing scores compared to ND (t(128) = -2.86; P = .014).

DISCUSSION

Current measures demonstrated moderate to good reliability. Longitudinal analysis revealed that SIB, BPT, and DLD changed with age depending on diagnostic progression; no change rates were dependent on baseline cognition, indicating usefulness across a variety of severity levels in DS.

Telomere Length Inheritance and Shortening in Trisomy 21

Objective: Trisomy 21 is a genetic disorder that shows premature aging symptoms. As an aging marker, telomere length is therefore of importance in trisomy families. Methods: We included 63 maternally originated trisomy 21 and 77 control families with infants in the first data set; 48 trisomy 21 and 60 control children in the second set; and 14 paternally originated trisomy 21 families in the third data set. We used Southern blot to measure the telomere length. Results: (1) Offsprings' telomere length increased with parents' age (p < .0001). (2) Trisomy 21 infants had longer telomere than the controls (p < .0001). (3) Post-birth, the telomere attrition rate was higher in cases than in controls (58 bps/year vs. 38 bps/year). Conclusion: (1) Our data supports the older parents-longer gamete telomere hypothesis. (2) Trisomy 21 patients are born with longer telomeres, (3) with advancing trisomy 21 age, the telomere shortens more quickly than euploids.

Language skills as a predictor of cognitive decline in adults with Down syndrome

INTRODUCTION

Adults with Down syndrome (DS) are at high risk for early onset Alzheimer's disease (AD), characterized by a progressive decline in multiple cognitive domains including language, which can impact social interactions, behavior, and quality of life. This cross-sectional study examined the relationship between language skills and dementia.

METHODS

A total of 168 adults with DS (mean age = 51.4 years) received neuropsychological assessments, including Vineland Communication Domain, McCarthy Verbal Fluency, and Boston Naming Test, and were categorized in one of three clinical groups: cognitively stable (CS, 57.8%); mild cognitive impairment (MCI-DS, 22.6%); and probable/definite dementia (AD-DS, 19.6%). Logistic regression was used to determine how well language measures predict group status.

RESULTS

Vineland Communication, particularly receptive language, was a significant predictor of MCI-DS. Semantic verbal fluency was the strongest predictor of AD-DS.

DISCUSSION

Assessment of language skills can aid in the identification of dementia in adults with DS. Clinically, indications of emerging language problems should warrant further evaluation and monitoring.

Promising outcome measures of early Alzheimer's dementia in adults with Down syndrome

INTRODUCTION

Adults with Down syndrome (DS) are at high risk for developing Alzheimer's disease (AD) and its associated dementia, warranting the development of strategies to improve early detection when prevention is possible.

METHODS

Using a broad battery of neuropsychological assessments, informant interviews, and clinical record review, we evaluated the psychometrics of measures in a large sample of 561 adults with DS. We tracked longitudinal stability or decline in functioning in a subsample of 269 participants over a period of 3 years, all initially without indications of clinically significant aging-related decline.

RESULTS

Results identified an array of objective measures that demonstrated sensitivity in distinguishing individuals with incident "mild cognitive impairment" (MCI-DS) as well as subsequent declines occurring with incident dementia.

DISCUSSION

Several instruments showed clear promise for use as outcome measures for future clinical trials and for informing diagnosis of individuals suspected of experiencing early signs and symptoms of a progressive dementia process.

Diagnosis of prodromal and Alzheimer's disease dementia in adults with Down syndrome using neuropsychological tests

INTRODUCTION

We aimed to define prodromal Alzheimer's disease (AD) and AD dementia using normative neuropsychological data in a large population-based cohort of adults with Down syndrome (DS).

METHODS

Cross-sectional study. DS participants were classified into asymptomatic, prodromal AD and AD dementia, based on neurologist's judgment blinded to neuropsychological data (Cambridge Cognitive Examination for Older Adults with Down's syndrome [CAMCOG-DS] and modified Cued Recall Test [mCRT]). We compared the cutoffs derived from the normative data in young adults with DS to those from receiver-operating characteristic curve (ROC) analysis.

RESULTS

Diagnostic performance of the CAMCOG-DS and modified Cued Recall Test (mCRT) in subjects with mild and moderate levels of intellectual disability (ID) was high, both for diagnosing prodromal AD and AD dementia (area under the curve [AUC] 0.73-0.83 and 0.90-1, respectively). The cutoffs derived from the normative data were similar to those derived from the ROC analyses.

DISCUSSION

Diagnosing prodromal AD and AD dementia in DS with mild and moderate ID using population norms for neuropsychological tests is possible with high diagnostic accuracy.

Proteomic profiles of incident mild cognitive impairment and Alzheimer's disease among adults with Down syndrome

INTRODUCTION

We sought to determine if proteomic profiles could predict risk for incident mild cognitive impairment (MCI) and Alzheimer's disease (AD) among adults with Down syndrome (DS).

METHODS

In a cohort of 398 adults with DS, a total of n = 186 participants were determined to be non-demented and without MCI or AD at baseline and throughout follow-up; n = 103 had incident MCI and n = 81 had incident AD. Proteomics were conducted on banked plasma samples from a previously generated algorithm.

RESULTS

The proteomic profile was highly accurate in predicting incident MCI (area under the curve [AUC] = 0.92) and incident AD (AUC = 0.88). For MCI risk, the support vector machine (SVM)-based high/low cut-point yielded an adjusted hazard ratio (HR) = 6.46 (P < .001). For AD risk, the SVM-based high/low cut-point score yielded an adjusted HR = 8.4 (P < .001).

DISCUSSION

The current results provide support for our blood-based proteomic profile for predicting risk for MCI and AD among adults with DS.

Down syndrome: Distribution of brain amyloid in mild cognitive impairment

INTRODUCTION

Down syndrome (DS) is associated with a higher risk of dementia. We hypothesize that amyloid beta (Aβ) in specific brain regions differentiates mild cognitive impairment in DS (MCI-DS) and test these hypotheses using cross-sectional and longitudinal data.

METHODS

18F-AV-45 (florbetapir) positron emission tomography (PET) data were collected to analyze amyloid burden in 58 participants clinically classified as cognitively stable (CS) or MCI-DS and 12 longitudinal CS participants.

RESULTS

The study confirmed our hypotheses of increased amyloid in inferior parietal, lateral occipital, and superior frontal regions as the main effects differentiating MCI-DS from the CS groups. The largest annualized amyloid increases in longitudinal CS data were in the rostral middle frontal, superior frontal, superior/middle temporal, and posterior cingulate cortices.

DISCUSSION

This study helps us to understand amyloid in the MCI-DS transitional state between cognitively stable aging and frank dementia in DS. The spatial distribution of Aβ may be a reliable indicator of MCI-DS in DS.

Disparities in diabetes management among medicaid recipients with intellectual and developmental disabilities (IDD): Evidence from five U.S. states

BACKGROUND

Diabetes is one of the most common chronic conditions among adults. Little is known about the quality of diabetes care received by adults with intellectual and developmental disabilities (IDD).

OBJECTIVE

To determine the extent to which the diabetes care needs are met for a population with both IDD and diabetes who are solely insured by Medicaid in five states (Iowa, Massachusetts, New York, Oregon and South Carolina).

METHODS

Medicaid administrative data in 2012 were used to identify Medicaid members (excluding dual eligibles) with diabetes and IDD in five states. Four diabetes care measures were compared between members with and without IDD using bivariate analyses. For those with diabetes and IDD, a logistic regression model was fitted for each state with the following predictors: age, sex, IDD subgroup, and occurrence of a specialist visit in the current or past year. A meta-analysis was then conducted to synthesize cross-state results.

RESULTS

Across the five states, 6229 (2%) of the 308,804 non-dual adult Medicaid members 18-64 years old with diabetes in 2012 also had IDD. Comparing those with IDD to their non-IDD peers on receipt of all four diabetes care measures showed differences by state, but state rates of overall adherence were very low, ranging from 16.6% to 28.5% of the population.

CONCLUSIONS

Meta-analysis results identified specialist visits as a strong predictor of adults with diabetes and IDD receiving all four components of diabetes care. This important information should be considered in efforts to improve quality care for this population.

Adaptation of the Clinical Dementia Rating Scale for adults with Down syndrome

Background

Adults with Down syndrome (DS) are at increased risk for Alzheimer disease dementia, and there is a pressing need for the development of assessment instruments that differentiate chronic cognitive impairment, acute neuropsychiatric symptomatology, and dementia in this population of patients.

Methods

We adapted a widely used instrument, the Clinical Dementia Rating (CDR) Scale, which is a component of the Uniform Data Set used by all federally funded Alzheimer Disease Centers for use in adults with DS, and tested the instrument among 34 DS patients recruited from the community. The participants were assessed using two versions of the modified CDR—a caregiver questionnaire and an in-person interview involving both the caregiver and the DS adult. Assessment also included the Dementia Scale for Down Syndrome (DSDS) and the Raven’s Progressive Matrices to estimate IQ.

Results

Both modified questionnaire and interview instruments captured a range of cognitive impairments, a majority of which were found to be chronic when accounting for premorbid function. Two individuals in the sample were strongly suspected to have early dementia, both of whom had elevated scores on the modified CDR instruments. Among individuals rated as having no dementia based on the DSDS, about half showed subthreshold impairments on the modified CDR instruments; there was substantial agreement between caregiver questionnaire screening and in-person interview of caregivers and DS adults.

Conclusions

The modified questionnaire and interview instruments capture a range of impairment in DS adults, including subthreshold symptomatology, and the instruments provide complementary information relevant to the ascertainment of dementia in DS. Decline was seen across all cognitive domains and was generally positively related to age and negatively related to IQ. Most importantly, adjusting instrument scores for chronic, premorbid impairment drastically shifted the distribution toward lower (no impairment) scores.

Laxative use among older adults with intellectual disability: a cross-sectional observational study

BACKGROUND

Chronic constipation is a prevalent issue in older people with intellectual disabilities and may have a significant negative impact on quality of life. The use of laxatives have not been adequately studied in this population.

OBJECTIVE

To examine laxatives in relation to prevalence, pattern, dosage, reported indication and correlates.

SETTING

Older people with intellectual disabilities who live independently, in community group homes or residential care in Ireland.

METHOD

Data was extracted from wave 2 (2013/2014) of the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing (IDS-TILDA). Descriptive statistics, bivariate analyses and multiple logistic regression were carried out. Laxative use was analysed using two indicators for chronic constipation, reported doctor's diagnosis of constipation and Rome III criteria.

MAIN OUTCOME MEASURE

Laxative use.

RESULTS

Among the cohort n = 677, chronic constipation was reported by 38.5% (n = 257). In total 41.5% (n = 281) reported 431 laxatives (mean ± 1.53 ± 0.74), with 74.3% (n = 209) of those with laxative use reporting chronic constipation. There were 40% (n = 113) who took 2 + laxatives, within which, 60% (n = 67) were using a combination from same laxative class. Reporting chronic constipation, living in residential care, exposure to anticholinergics and receiving soft/liquidized food were significantly associated with laxative use.

CONCLUSION

Chronic constipation and laxative use were highly prevalent in this study of older adults with intellectual disabilities. The treatment of constipation appeared to be unsystematic. Intra-class laxative use was frequent. There is a need for evidence-based treatment guidelines developed especially for people with intellectual disabilities to provide effective, quality care.

Task and Participant Variables Predict Communication Complexity Scale (CCS) Scores: Closer Examination of the CCS

Communication Complexity Scale (CCS) scores for 269 minimally verbal participants were examined to determine if communicator behavior and task and communicator characteristics were related to scores in a manner consistent with theoretical and research evidence expectations. Each participant completed an interactive assessment with 6 joint attention tasks and 6 behavior regulation tasks. Caregivers completed the Vineland Adaptive Behavior Scales II. Results indicated (a) joint attention tasks yielded lower scores than behavior regulation tasks, (b) older participants had lower scores, (c) individuals with autism spectrum disorder scored more similarly than those without, (d) the difference between joint attention and behavior regulation scores was greater for the autism spectrum disorder group, and (e) adaptive behavior was significantly positively related to complexity scores.

Neuropsychological and neurophysiological characterization of mild cognitive impairment and Alzheimer's disease in Down syndrome

Down syndrome (DS) has been considered a unique model for the investigation of Alzheimer's disease (AD) but intermediate stages in the continuum are poorly defined. Considering this, we investigated the neurophysiological (i.e., magnetoencephalography [MEG]) and neuropsychological patterns of mild cognitive impairment (MCI) and AD in middle-aged adults with DS. The sample was composed of four groups: Control-DS (n = 14, mean age 44.64 ± 3.30 years), MCI-DS (n = 14, 51.64 ± 3.95 years), AD-DS (n = 13, 53.54 ± 6.58 years), and Control-no-DS (healthy controls, n = 14, 45.21 ± 4.39 years). DS individuals were studied with neuropsychological tests and MEG, whereas the Control-no-DS group completed only the MEG session. Our results showed that the AD-DS group exhibited a significantly poorer performance as compared with the Control-DS group in all tests. Furthermore, this effect was crucially evident in AD-DS individuals when compared with the MCI-DS group in verbal and working memory abilities. In the neurophysiological domain, the Control-DS group showed a widespread increase of theta activity when compared with the Control-no-DS group. With disease progression, this increased theta was substituted by an augmented delta, accompanied with a reduction of alpha activity. Such spectral pattern-specifically observed in occipital, posterior temporal, cuneus, and precuneus regions-correlated with the performance in cognitive tests. This is the first MEG study in the field incorporating both neuropsychological and neurophysiological information, and demonstrating that this combination of markers is sensitive enough to characterize different stages along the AD continuum in DS.

Frontal-subcortical behaviors during Alzheimer's disease in individuals with Down syndrome

There is evidence that frontal-subcortical circuits play an important role in the initial presentation of dementia in Down syndrome (DS), including changes in behavior, a decline in working memory and executive dysfunction. We evaluated 92 individuals with DS (≥30 years of age), divided into 3 groups by diagnosis-stable cognition, prodromal dementia, and Alzheimer's disease. Each individual was evaluated with an executive protocol developed for people with intellectual disabilities and was rated for behaviors related to frontal lobe dysfunction (disinhibition, executive dysfunction, and apathy) by an informant using the Frontal Systems Behavior Scale. Informant-reported behaviors related to frontal lobe dysfunction were found to correlate negatively with executive function performance. Disinhibition and executive dysfunction were associated with the clinical stage of dementia. The odds of having Alzheimer's disease increased in parallel with increases in the domain and total Frontal Systems Behavior Scale scores (p ≤ 0.5). Disinhibition, executive dysfunction and apathy should be taken into consideration during the clinical evaluation of adults with DS, and future studies should consider the intersection of neuropathology, brain connectivity, and behavior.

Dementia in Down syndrome: unique insights for Alzheimer disease research

Virtually all adults with Down syndrome (DS) show the neuropathological changes of Alzheimer disease (AD) by the age of 40 years. This association is partially due to overexpression of amyloid precursor protein, encoded by APP, as a result of the location of this gene on chromosome 21. Amyloid-β accumulates in the brain across the lifespan of people with DS, which provides a unique opportunity to understand the temporal progression of AD and the epigenetic factors that contribute to the age of dementia onset. This age dependency in the development of AD in DS can inform research into the presentation of AD in the general population, in whom a longitudinal perspective of the disease is not often available. Comparison of the risk profiles, biomarker profiles and genetic profiles of adults with DS with those of individuals with AD in the general population can help to determine common and distinct pathways as well as mechanisms underlying increased risk of dementia. This Review evaluates the similarities and differences between the pathological cascades and genetics underpinning DS and AD with the aim of providing a platform for common exploration of these disorders.

Cognitive markers of preclinical and prodromal Alzheimer's disease in Down syndrome

INTRODUCTION

Down syndrome (DS) is associated with an almost universal development of Alzheimer's disease. Individuals with DS are therefore an important population for randomized controlled trials to prevent or delay cognitive decline, though it is essential to understand the time course of early cognitive changes.

METHODS

We conducted the largest cognitive study to date with 312 adults with DS to assess age-related and Alzheimer's disease-related cognitive changes during progression from preclinical to prodromal dementia, and prodromal to clinical dementia.

RESULTS

Changes in memory and attention measures were most sensitive to early decline. Resulting sample size calculations for randomized controlled trials to detect significant treatment effects to delay decline were modest.

DISCUSSION

Our findings address uncertainties around the development of randomized controlled trials to delay cognitive decline in DS. Such trials are essential to reduce the high burden of dementia in people with DS and could serve as proof-of-principle trials for some drug targets.

Differential expression of serum biomarkers in hemodialysis patients with mild cognitive decline: A prospective single-center cohort study

Studies suggest that hemodialysis patients are at a higher risk for cognitive decline than healthy individuals; however, underlying mechanisms have not been fully elucidated. We aimed to investigate the roles of serum biomarkers, such as brain-derived neurotrophic factor (BDNF), inflammatory cytokines, fibroblast growth factor (FGF)-23 and its co-receptor α-klotho and platelet (PLT) count in mild cognitive decline (MCD) of patients undergoing hemodialysis in this prospective cohort study. Serum levels of BDNF, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and the number of PLT were significantly altered in the MCD group compared with those in healthy controls (HCs) or those with normal cognitive function (NCF). Although serum α-klotho and FGF-23 levels were significantly altered in the MCD group, there were no statistical differences between the MCD and NCF groups. Serum BDNF levels and PLT counts were significantly correlated with cognitive test scores. Receiver operating characteristic (ROC) curves demonstrated that BDNF and PLT were potential biomarkers for improved MCD diagnosis in patients with hemodialysis. These findings suggest that hemodialysis-related MCD is associated with altered BDNF, TNF-α and IL-6 levels as well as PLT counts and that serum BDNF levels and PLT counts are potential biomarkers for hemodialysis-related MCD diagnosis.

Analysis of the linguistic profile in down syndrome using the arizona battery for communication disorders of dementia - a pilot study

PURPOSE

To characterize the linguistic profile of adults and elderly with Down Syndrome (DS) using the Arizona Battery for Communication Disorders of Dementia (ABCD).

METHODS

Thirty adult individuals with DS were evaluated through the MoCA cognitive battery, four functional scales (Pfeffer, Lawton-IADL, Katz-IADL and IQCODE) and the ABCD battery, which evaluates Mental State, Episodic Memory, Linguistic Expression, Linguistic Comprehension and Visuospatial Construction. The scores obtained by the individuals in the ABCD were correlated to those obtained on the Lawton-IADL scale.

RESULTS

Individuals with DS had significantly lower performance than cognitively normal adults and elderly as described in Brazilian studies. Due to the lack of similar studies in our country, we compared our results to those of elderly with Alzheimer's Disease (AD), verifying that the performance of the DS population is similar to that of AD patients, although the former presented better scores on episodic immediate memory tests. There was a significant positive correlation between the scores obtained in the Lawton-IADL and those on the constructs Mental State, Episodic Memory, Linguistic Comprehension and Total ABCD.

CONCLUSION

The ABCD battery is a useful tool in the evaluation of adults and elderly with DS and the performance of individuals in this battery correlates with indices of functionality. This is a pioneer study in Brazil, and it points to the need for a better characterization of the linguistic abilities of individuals with DS, in order to allow the elaboration of strategies that stimulate their communicative abilities as to promote greater social insertion for this population.

Anomalous White Matter Structure and the Effect of Age in Down Syndrome Patients

BACKGROUND

Neural tissue alterations in Down syndrome are fully expressed at relatively late developmental stages. In addition, there is an early presence of neurodegenerative changes in the late life stages.

OBJECTIVE

The aims of this study were both to characterize white matter abnormalities in the brain of adult Down syndrome patients using diffusion tensor imaging (DTI) and to investigate whether degenerative alterations in white matter structure are detectable before dementia is clinically evident.

METHODS

Forty-five adult non-demented Down syndrome patients showing a wide age range (18-52 years) and a matched 45-subject control group were assessed. DTI fractional anisotropy (FA) brain maps were generated and selected cognitive tests were administered.

RESULTS

Compared with healthy controls, non-demented Down syndrome patients showed lower DTI FA in white matter involving the major pathways, but with more severe alterations in the frontal-subcortical circuits. White matter FA decreased with age at a similar rate in both DS and control groups.

CONCLUSIONS

Our results contribute to characterizing the expression of white matter structural alterations in adult Down syndrome. However, an accelerated aging effect was not demonstrated, which may suggest that the FA measurements used are not sufficiently sensitive or, alternatively, age-related white matter neurodegeneration is not obvious prior to overt clinical dementia.

A longitudinal study of brain anatomy changes preceding dementia in Down syndrome

Background

We longitudinally assessed Down syndrome individuals at the age of risk of developing dementia to measure changes in brain anatomy and their relationship to cognitive impairment progression.

Methods

Forty-two Down syndrome individuals were initially included, of whom 27 (mean age 46.8 years) were evaluable on the basis of completing the 2-year follow-up and success in obtaining good quality MRI exams. Voxel-based morphometry was used to estimate regional brain volumes at baseline and follow-up on 3D anatomical images. Longitudinal volume changes for the group and their relationship with change in general cognitive status and specific cognitive domains were mapped.

Results

As a group, significant volume reduction was identified in the substantia innominata region of the basal forebrain, hippocampus, lateral temporal cortex and left arcuate fasciculus. Volume reduction in the substantia innominata and hippocampus was more prominent in individuals whose clinical status changed from cognitively stable to mild cognitive impairment or dementia during the follow-up. Relevantly, longitudinal memory score change was specifically associated with volume change in the hippocampus, prospective memory with prefrontal lobe and verbal comprehension with language-related brain areas.

Conclusions

Results are notably concordant with the well-established anatomical changes signaling the progression to dementia in Alzheimer's disease, despite the dense baseline pathology that developmentally accumulates in Down syndrome. This commonality supports the potential value of Down syndrome as a genetic model of Alzheimer's neurodegeneration and may serve to further support the view that Down syndrome patients are best candidates to benefit from treatment research in Alzheimer's disease.

Exosomal biomarkers in Down syndrome and Alzheimer's disease

Every person with Down syndrome (DS) has the characteristic features of Alzheimer's disease (AD) neuropathology in their brain by the age of forty, and most go on to develop AD dementia. Since people with DS show highly variable levels of baseline function, it is often difficult to identify early signs of dementia in this population. The discovery of blood biomarkers predictive of dementia onset and/or progression in DS is critical for developing effective clinical diagnostics. Our recent studies show that neuron-derived exosomes, which are small extracellular vesicles secreted by most cells in the body, contain elevated levels of amyloid-beta peptides and phosphorylated-Tau that could indicate a preclinical AD phase in people with DS starting in childhood. We also found that the relative levels of these biomarkers were altered following dementia onset. Exosome release and signaling are dependent on cellular redox homeostasis as well as on inflammatory processes, and exosomes may be involved in the immune response, suggesting a dual role as both triggers of inflammation in the brain and propagators of inflammatory signals between brain regions. Based on recently reported connections between inflammatory processes and exosome release, the elevated neuroinflammatory state observed in people with DS may affect exosomal AD biomarkers. Herein, we discuss findings from studies of people with DS, people with DS and AD (DS-AD), and mouse models of DS showing new connections between neuroinflammatory pathways, oxidative stress, exosomes, and exosome-mediated signaling, which may inform future AD diagnostics, preventions, and treatments in the DS population as well as in the general population.

Longitudinal telomere shortening and early Alzheimer's disease progression in adults with down syndrome

Telomere shortening was shown to parallel Alzheimer's disease (AD) associated dementia. By using a dual PNA Probe system we have developed a practical method for comparing telomere length in T-lymphocyte interphases from individuals with Down syndrome (DS) with and without "mild cognitive impairment" (MCI-DS) and demonstrated that telomere length can serve as a valid biomarker for the onset of MCI-DS in this high-risk population. To verify progressive cognitive decline we have now examined sequential changes in telomere length in 10 adults with DS (N = 4 Female, N = 6 Male) developing MCI-DS. Cases were selected blind to telomere length from a sample of adults with DS previously enrolled in a prospective longitudinal study at 18-month intervals with clinical and telomere assessments: (1) MCI-DS group data were collected approximately three years prior to development of MCI-DS; (2) 18 months later; (3) when MCI-DS was first observed. These telomere measures were compared to those from another 10 adults with DS matched by sex and approximate age but without indications of MCI-DS (Controls). PNA (peptide nucleic acid) probes for telomeres together with a chromosome two centromere probe were used. Findings indicated telomere shortening over time for both Cases and Controls. Group differences emerged by 18-months prior to recognition of MCI-DS onset and completely non-overlapping distributions of telomere measures were observed by the time of MCI-DS onset. This study adds to accumulating evidence of the value of telomere length, as an early biomarker of AD progression in adults with Down syndrome.

Consensus Statement of the International Summit on Intellectual Disability and Dementia Related to Nomenclature

A working group of the 2016 International Summit on Intellectual Disability and Dementia was charged to examine the terminology used to define and report on dementia in publications related to intellectual disability (ID). A review of related publications showed mixed uses of terms associated with dementia or causative diseases. As with dementia research in the non-ID population, language related to dementia in the ID field often lacks precision and could lead to a misunderstanding of the condition(s) under discussion, an increasingly crucial issue given the increased global attention dementia is receiving in that field. Most articles related to ID and dementia reporting clinical or medical research generally provide a structured definition of dementia or related terms; social care articles tend toward term use without definition. Toward terminology standardization within studies/reports on dementia and ID, the Summit recommended that a consistent approach is taken that ensures (a) growing familiarity with dementia-related diagnostic, condition-specific, and social care terms (as identified in the working group's report); (b) creating a guidance document on accurately defining and presenting information about individuals or groups referenced; and

Outcome Measures for Clinical Trials in Down Syndrome

Increasingly individuals with intellectual and developmental disabilities, including Down syndrome, are being targeted for clinical trials. However, a challenge exists in effectively evaluating the outcomes of these new pharmacological interventions. Few empirically evaluated, psychometrically sound outcome measures appropriate for use in clinical trials with individuals with Down syndrome have been identified. To address this challenge, the National Institutes of Health (NIH) assembled leading clinicians and scientists to review existing measures and identify those that currently are appropriate for trials; those that may be appropriate after expansion of age range addition of easier items, and/or downward extension of psychometric norms; and areas where new measures need to be developed. This article focuses on measures in the areas of cognition and behavior.

An improved method for detecting telomere size differences in T-lymphocyte interphases from older people with Down syndrome with and without mild cognitive impairment

Telomere size (quantified by fluorescence intensity and physical lengths) in short-term T-lymphocyte cultures from adults with Down syndrome (DS) with and without mild cognitive impairment (MCI-DS) or dementia was compared. For these studies, dementia status was determined based on longitudinal assessments employing a battery of cognitive and functional assessments developed to distinguish adult-onset impairment from preexisting developmental disability. In the course of our studies using a MetaSystems Image Analyzer in combination with ISIS software and a Zeiss Axioskop 2, we found that Fluorescein isothiocyanate (FITC) telomere fluorescence referenced to chromosome 2-identified FITC probe fluorescence as a nontelomere standard (telomere/cen2 ratio) showed great promise as a biomarker of early decline associated with Alzheimer's disease (AD) in this high-risk population. We have now obtained a cen (2) CY3 probe that can clearly be distinguished from the blue-green FITC interphase telomere probe, providing a clear distinction between telomere and centromere fluorescence in both interphase and metaphase. We used FITC/CY3 light intensity ratios to compare telomere length in interphases in adults with DS with and without MCI-DS or dementia. Five age-matched female and five age-matched male pairs (n = 10) all showed clear evidence of telomere shortening associated with clinical progression of AD (P < 0.002 - P < 0.000001), with distributions of mean values for cases and controls showing no overlap. We also examined the time needed for microscopy using interphase versus metaphase fluorescence preparations. With interphase preparations, examination time was reduced by an order of magnitude compared with metaphase preparations, indicating that the methods employed herein have considerable practical promise for translation into broad diagnostic practice.

Health care utilisation among older persons with intellectual disability and dementia: a registry study

BACKGROUND

Both persons with intellectual disability (ID) and persons with dementia have high disease burdens, and consequently also high health care needs. As life expectancy increases for persons with ID, the group of persons with the dual diagnosis of ID and dementia will become larger.

METHOD

Through national registries, we identified 7936 persons who had received support directed to persons with ID during 2012, and an age- and gender-matched sample from the general population. A national registry was also used to collect information on health care utilisation (excluding primary care) for the period 2002-2012. Health care utilisation was measured as presence and number of planned and unplanned in-patient and out-patient visits, as well as length of stay.

RESULTS

In comparison with persons with ID but without dementia, persons with ID and dementia were more likely to have at least one planned out-patient visit (odds ratio [OR] 8.07), unplanned out-patient visit (OR 2.41), planned in-patient visit (OR 2.76) or unplanned in-patient visit (OR 4.19). However, among those with at least one of each respective outcome, the average number of visits did not differ between those with and without dementia. Persons with ID and dementia were less likely to have at least one planned out-patient visit than persons with dementia in the general population sample (OR 0.40), but more likely to have at least one unplanned in-patient visit (OR 1.90). No statistically significant differences were found for having at least one unplanned out-patient or planned in-patient visit. Nevertheless, among those with at least one unplanned out-patient visit, the number of visits was higher in the general population sample.

CONCLUSIONS

Persons with ID and dementia are less likely to receive planned health care than persons with dementia in the general population. They have, however, higher levels of unplanned health care utilisation. This may be an indication that the current support system is not sufficient to meet the challenges of increased longevity among persons with ID.

A critical literature review of the effectiveness of various instruments in the diagnosis of dementia in adults with intellectual disabilities

Introduction

Currently, there is no consensus on dementia diagnostics in adults with intellectual disabilities (ID). There are three types of assessments available: direct cognitive tests, test batteries, and informant reports.

Methods

A systematic literature search was conducted in four databases yielding 9840 records. Relevant studies were identified and selected using predefined inclusion and exclusion criteria and then coded and classified according to assessment type. This was completed by two independent researchers, with a third consulted when discrepancies arose. The review collates diagnostic instruments and presents strengths and weaknesses.

Results

Overall 47 studies met the search criteria, and 43 instruments were extracted from the selected studies. Of which, 10 instruments were classified as test batteries, 23 were classified as direct cognitive tests, and the remaining 10 were informant reports.

Discussion

This review can recommend that cognitive test batteries can offer the most practical and efficient method for dementia diagnosis in individuals with ID.

Telomere longitudinal shortening as a biomarker for dementia status of adults with Down syndrome

Previous studies have suggested that Alzheimer's disease (AD) causes an accelerated shortening of telomeres, the ends of chromosomes consisting of highly conserved TTAGGG repeats that, because of unidirectional 5'-3' DNA synthesis, lose end point material with each cell division. Our own previous work suggested that telomere length of T-lymphocytes might be a remarkably accurate biomarker for "mild cognitive impairment" in adults with Down syndrome (MCI-DS), a population at dramatically high risk for AD. To verify that the progression of cognitive and functional losses due to AD produced this observed telomere shortening, we have now examined sequential changes in telomere length in five individuals with Down syndrome (3F, 2M) as they transitioned from preclinical AD to MCI-DS (N = 4) or dementia (N = 1). As in our previous studies, we used PNA (peptide nucleic acid) probes for telomeres and the chromosome 2 centromere (as an "internal standard" expected to be unaffected by aging or dementia status), with samples from the same individuals now collected prior to and following development of MCI-DS or dementia. Consistent shortening of telomere length was observed over time. Further comparisons with our previous cross-sectional findings indicated that telomere lengths prior to clinical decline were similar to those of other adults with Down syndrome (DS) who have not experienced clinical decline while telomere lengths following transition to MCI-DS or dementia in the current study were comparable to those of other adults with DS who have developed MCI-DS or dementia. Taken together, findings indicate that telomere length has significant promise as a biomarker of clinical progression of AD for adults with DS, and further longitudinal studies of a larger sample of individuals with DS are clearly warranted to validate these findings and determine if and how factors affecting AD risk also influence these measures of telomere length.

Cerebrovascular contributions to aging and Alzheimer's disease in Down syndrome

Down syndrome (DS) is a common cause of intellectual disability and is also associated with early age of onset of Alzheimer's disease (AD). Due to an extra copy of chromosome 21, most adults over 40years old with DS have beta-amyloid plaques as a result of overexpression of the amyloid precursor protein. Cerebrovascular pathology may also be a significant contributor to neuropathology observed in the brains of adults with DS. This review describes the features of cardiovascular dysfunction and cerebrovascular pathology in DS that may be modifiable risk factors and thus targets for interventions. We will describe cerebrovascular pathology, the role of co-morbidities, imaging studies indicating vascular pathology and the possible consequences. It is clear that our understanding of aging and AD in people with DS will benefit from further studies to determine the role that cerebrovascular dysfunction contributes to cognitive health. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Rapid assessment of cognitive function in down syndrome across intellectual level and dementia status

BACKGROUND

Adults with Down syndrome (DS) are at risk of developing dementia and cognitive assessment is a fundamental part of the diagnostic process. Previously, we developed a Rapid Assessment for Developmental Disabilities (RADD), a brief, broadly focused direct test of cognition. In the current report, we assess whether the RADD is sensitive to dementia in DS and the degree to which it compares with other cognitive measures of dementia in this population.

METHODS

In a sample of 114 individuals with DS, with dementia diagnosed in 62%, the RADD was compared with the Dementia Questionnaire for Mentally Retarded Persons (DMR), the Bristol Activities of Daily Living Scale, Severe Impairment Battery (SIB), and the Brief Praxis Test (BPT).

RESULTS

The RADD showed predicted effects across intellectual disability (ID) levels and dementia status (p < 0.001). Six-month test-retest reliability for the subset of individuals without dementia was high (r(41) = 0.95, p < 0.001). Criterion-referenced validity was demonstrated by correlations between RADD scores and ID levels based upon prior intelligence testing and clinical diagnoses (rs (114) = 0.67, p = 0.001) and with other measures of cognitive skills, such as the BPT, SIB, and DMR-Sum of Cognitive scores (range 0.84 through 0.92). Using receiver operating characteristic curves for groups varying in pre-morbid severity of ID, the RADD exhibited high sensitivity (0.87) and specificity (0.81) in discriminating among individuals with and without dementia, although sensitivity was somewhat lower (0.73) for the subsample of dementia cases diagnosed no more than 2 years prior to their RADD assessment.

CONCLUSION

Taken together, findings indicated that the RADD, a relatively brief, easy-to-administer test for cognitive function assessment across ID levels and dementia status, would be a useful component of cognitive assessments for adults with DS, including assessments explicitly focused on dementia.

Patterns of Performance on the Modified Cued Recall Test in Spanish Adults With Down Syndrome With and Without Dementia

The assessment of memory decline in people with intellectual disability (ID) is more difficult than in the general population, due to a lack of appropriate instruments and to preexisting cognitive impairment. The aim of this study was to describe performance of healthy adults with Down syndrome (healthy-DS; prospectively cohort) on a Spanish version of the modified Cued Recall Test (mCRT). We also recruited retrospectively a cohort of DS subjects with Dementia of the Alzheimer's Type (DS-DAT). Healthy-DS obtained higher scores on free recall and total score than DS-DAT. Age was the main factor associated with decreasing mCRT scores. The mCRT was useful in DS subjects with ID at the upper end of the spectrum or ID in the middle range of the spectrum, and discriminated well between DS subjects with and without DAT.

Quantitative Electroencephalography as a Diagnostic Tool for Alzheimer's Dementia in Adults with Down Syndrome

Background

Assessment of dementia in individuals with intellectual disability is complex due to great inter-individual variability in cognitive function prior to dementia and a lack of standardized instruments. Studies have indicated that quantitative electroencephalography (qEEG) results may be used as a diagnostic marker for dementia. The aim of this study was to examine the value of qEEG in the diagnostic evaluation of dementia in patients with Down syndrome (DS).

Method

The study included 21 patients with DS and mild-to-moderate dementia due to Alzheimer's disease (DS-AD) and 16 age-matched adults with DS without cognitive deterioration assessed by the informant-based Dementia Screening Questionnaire in Intellectual Disability (DSQIID). Conventional EEG was performed and analysed quantitatively using fast Fourier transformation. Outcomes were centroid frequency, peak frequency, absolute power, and relative power.

Results

In several regions of the brain, a significant decrease in the theta-1 band (4-7 Hz) was identified for the centroid frequency. A significant negative correlation was demonstrated between the mean of the centroid frequency of the theta-1 band and the total DSQIID score.

Conclusion

We found that qEEG can detect a significant decrease in centroid frequency in a sample of patients with DS-AD as compared to a sample of adults with DS and no cognitive deterioration.

Association between adaptive behaviour and age in adults with Down syndrome without dementia: examining the range and severity of adaptive behaviour problems

BACKGROUND

Studies on adaptive behaviour and ageing in adults with Down syndrome (DS) (without dementia) have typically analysed age-related change in terms of the total item scores on questionnaires. This research extends the literature by investigating whether the age-related changes in adaptive abilities could be differentially attributed to changes in the number or severity (intensity) of behavioural questionnaire items endorsed.

METHODS

The Adaptive Behaviour Assessment System-II Adult (ABAS-II Adult) was completed by parents and caregivers of 53 adults with DS aged between 16 and 56 years. Twenty adults with DS and their parents/caregivers were a part of a longitudinal study, which provided two time points of data. In addition 33 adults with DS and their parents/caregivers from a cross-sectional study were included. Random effects regression analyses were used to examine the patterns in item scores associated with ageing.

RESULTS

Increasing age was found to be significantly associated with lower adaptive behaviour abilities for all the adaptive behaviour composite scores, expect for the practical composite. These associations were entirely related to fewer ABAS-II Adult items being selected as present for the older participants, as opposed to the scores being attributable to lower item severity.

CONCLUSIONS

This study provides evidence for a differential pattern of age-related change for various adaptive behaviour skills in terms of range, but not severity. Possible reasons for this pattern will be discussed. Overall, these findings suggest that adults with DS may benefit from additional support in terms of their social and conceptual abilities as they age.

Catatonia in Down syndrome; a treatable cause of regression

OBJECTIVE

The main aim of this case series report is to alert physicians to the occurrence of catatonia in Down syndrome (DS). A second aim is to stimulate the study of regression in DS and of catatonia. A subset of individuals with DS is noted to experience unexplained regression in behavior, mood, activities of daily living, motor activities, and intellectual functioning during adolescence or young adulthood. Depression, early onset Alzheimer's, or just "the Down syndrome" are often blamed after general medical causes have been ruled out. Clinicians are generally unaware that catatonia, which can cause these symptoms, may occur in DS.

STUDY DESIGN

Four DS adolescents who experienced regression are reported. Laboratory tests intended to rule out causes of motor and cognitive regression were within normal limits. Based on the presence of multiple motor disturbances (slowing and/or increased motor activity, grimacing, posturing), the individuals were diagnosed with unspecified catatonia and treated with anti-catatonic treatments (benzodiazepines and electroconvulsive therapy [ECT]).

RESULTS

All four cases were treated with a benzodiazepine combined with ECT and recovered their baseline functioning.

CONCLUSION

We suspect catatonia is a common cause of unexplained deterioration in adolescents and young adults with DS. Moreover, pediatricians and others who care for individuals with DS are generally unfamiliar with the catatonia diagnosis outside schizophrenia, resulting in misdiagnosis and years of morbidity. Alerting physicians to catatonia in DS is essential to prompt diagnosis, appropriate treatment, and identification of the frequency and course of this disorder.

Telomere shortening in Down syndrome patients--when does it start?

Down syndrome (DS) is one of the most common aneuploidy. In general population, its prevalence is 1:600-1:800 live births. It is caused by a trisomy of chromosome 21. DS is phenotypically manifested by premature aging, upward slant to the eyes, epicanthus, flattened face, and poor muscle tone. In addition to physical changes, this syndrome is characterized by early onset of diseases specific to old age, such as Alzheimer's disease, vision and hearing problems, and precocious menopause. Since DS symptoms include premature aging, the shortening of telomeres might be one of the markers of cellular aging. Consequently, the aim of the study was to determine the length of the telomeres in leukocytes from the blood of juvenile patients with DS (n=68) compared to an age-matched control group (n=56) and also to determine the diagnostic or predictive value for this parameter. We show that, for the first time, in juveniles, the average relative telomere length in studied subjects is significantly longer than in the control group (50.46 vs. 40.56, respectively arbitrary units [AU]; p=0.0026). The results provide interesting basis for further research to determine the causes and consequences of telomere maintaining and the dynamics of this process in patients with DS.