Normal ageing in adults with Down's syndrome: a longitudinal study

Aberrant crosstalk between insulin signaling and mTOR in young Down syndrome individuals revealed by neuronal-derived extracellular vesicles

INTRODUCTION

Intellectual disability, accelerated aging, and early-onset Alzheimer-like neurodegeneration are key brain pathological features of Down syndrome (DS). Although growing research aims at the identification of molecular pathways underlying the aging trajectory of DS population, data on infants and adolescents with DS are missing.

METHODS

Neuronal-derived extracellular vesicles (nEVs) were isolated form healthy donors (HDs, n = 17) and DS children (n = 18) from 2 to 17 years of age and nEV content was interrogated for markers of insulin/mTOR pathways.

RESULTS

nEVs isolated from DS children were characterized by a significant increase in pIRS1^Ser636 , a marker of insulin resistance, and the hyperactivation of the Akt/mTOR/p70S6K axis downstream from IRS1, likely driven by the higher inhibition of Phosphatase and tensin homolog (PTEN). High levels of pGSK3β^Ser9 were also found.

CONCLUSIONS

The alteration of the insulin-signaling/mTOR pathways represents an early event in DS brain and likely contributes to the cerebral dysfunction and intellectual disability observed in this unique population.

Capturing cognitive and behavioral variability among individuals with Down syndrome: a latent profile analysis

BACKGROUND

There is a high degree of inter- and intra-individual variability observed within the phenotype of Down syndrome. The Down Syndrome Cognition Project was formed to capture this variability by developing a large nationwide database of cognitive, behavioral, health, and genetic information on individuals with Down syndrome, ages 6-25 years. The current study used the Down Syndrome Cognition Project database to characterize cognitive and behavioral variability among individuals with Down syndrome.

METHODS

Latent profile analysis was used to identify classes across a sample of 314 participants based on their cognition (IQ and executive functioning), adaptive and maladaptive behavior, and autism spectrum disorder symptomatology. A multivariate multinomial regression model simultaneously examined demographic correlates of class.

RESULTS

Results supported a 3-class model. Each class demonstrated a unique profile across the subdomains of cognition and behavior. The "normative" class was the largest (n = 153, 48%) and displayed a relatively consistent profile of cognition and adaptive behavior, with low rates of maladaptive behavior and autism symptomatology. The "cognitive" class (n = 109, 35%) displayed low cognitive scores and adaptive behavior and more autism symptomatology, but with low rates of maladaptive behavior. The "behavioral" class, the smallest group (n = 52, 17%), demonstrated higher rates of maladaptive behavior and autism symptomatology, but with cognition levels similar to the "normative" class; their adaptive behavior scores fell in between the other two classes. Household income and sex were the only demographic variables to differ among classes.

CONCLUSIONS

These findings highlight the importance of subtyping the cognitive and behavioral phenotype among individuals with Down syndrome to identify more homogeneous classes for future intervention and etiologic studies. Results also demonstrate the feasibility of using latent profile analysis to distinguish subtypes in this population. Limitations and future directions are discussed.

Screening of Cognitive Changes in Adults with Intellectual Disabilities: A Systematic Review

Background and Aims: Screening and assessment of cognitive changes in adults with Intellectual Disabilities (ID), mainly Down Syndrome (DS), is crucial to offer appropriate services to their needs. We present a systematic review of the existing instruments assessing dementia, aiming to support researchers and clinicians’ best practice. Methods: Searches were carried out in the databases Web of Science; PubMed; PsycINFO in March 2019 and updated in October 2020. Studies were selected and examined if they: (1) focused on assessing age-related cognitive changes in persons with ID; (2) included adults and/or older adults; (3) included scales and batteries for cognitive assessment. Results: Forty-eight cross-sectional studies and twenty-seven longitudinal studies were selected representing a total sample of 6451 participants (4650 DS and 1801 with other ID). In those studies, we found 39 scales, questionnaires, and inventories, and 13 batteries for assessing cognitive and behavioural changes in adults with DS and other ID. Conclusion: The most used instrument completed by an informant or carer was the Dementia Questionnaire for Learning Disabilities (DLD), and its previous versions. We discuss the strengths and limitations of the instruments and outline recommendations for future use.

Intelligence trajectories in adolescents and adults with down syndrome: Cognitively stimulating leisure activities mitigate health and ADL problems

GOALS

This study examined: (a) crystallized/fluid intelligence trajectories of adolescents and adults with Down syndrome; and (b) the contribution of endogenous (health, activities of daily living-ADL) and exogenous (cognitively stimulating leisure activities) factors on adults' intelligence with age.

METHOD

Four cohorts (N = 80) with Down syndrome participated: adolescents (ages 16-21) and adults (ages 30-45, 46-60 and 61+). All completed Vocabulary and Similarities (crystallized) and Block Design and Raven (fluid) intelligence tests (WAIS-III^HEB , Wechsler, 2001).

RESULTS

The 30-45 cohort significantly outperformed the 16-21 cohort. Except for Vocabulary, which remained stable, onset of decline was at 40-50. Age-related declining health and ADL correlated with participants' lower fluid intelligence, but cognitive leisure activities mitigated this influence.

CONCLUSIONS

Intelligence development into adulthood supported the continuous trajectory and compensation age theory, rather than accelerated or stable trajectories. Not only endogenous factors but also exogenous factors determined intelligence levels in adults with Down syndrome, supporting cognitive activity theory.

The Alzheimer's Biomarker Consortium-Down Syndrome: Rationale and methodology

INTRODUCTION

Adults with Down syndrome (DS) are at exceptionally high risk for Alzheimer's disease (AD), with virtually all individuals developing key neuropathological features by age 40. Identifying biomarkers of AD progression in DS can provide valuable insights into pathogenesis and suggest targets for disease modifying treatments.

METHODS

We describe the development of a multi-center, longitudinal study of biomarkers of AD in DS. The protocol includes longitudinal examination of clinical, cognitive, blood and cerebrospinal fluid-based biomarkers, magnetic resonance imaging and positron emission tomography measures (at 16-month intervals), as well as genetic modifiers of AD risk and progression.

RESULTS

Approximately 400 individuals will be enrolled in the study (more than 370 to date). The methodological approach from the administrative, clinical, neuroimaging, omics, neuropathology, and statistical cores is provided.

DISCUSSION

This represents the largest U.S.-based, multi-site, biomarker initiative of AD in DS. Findings can inform other multidisciplinary networks studying AD in the general population.

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.

Clinical and biomarker changes of Alzheimer's disease in adults with Down syndrome: a cross-sectional study

BACKGROUND

Alzheimer's disease and its complications are the leading cause of death in adults with Down syndrome. Studies have assessed Alzheimer's disease in individuals with Down syndrome, but the natural history of biomarker changes in Down syndrome has not been established. We characterised the order and timing of changes in biomarkers of Alzheimer's disease in a population of adults with Down syndrome.

METHODS

We did a dual-centre cross-sectional study of adults with Down syndrome recruited through a population-based health plan in Barcelona (Spain) and through services for people with intellectual disabilities in Cambridge (UK). Cognitive impairment in participants with Down syndrome was classified with the Cambridge Cognitive Examination for Older Adults with Down Syndrome (CAMCOG-DS). Only participants with mild or moderate disability were included who had at least one of the following Alzheimer's disease measures: apolipoprotein E allele carrier status; plasma concentrations of amyloid β peptides 1-42 and 1-40 and their ratio (Aβ_1-42/1-40), total tau protein, and neurofilament light chain (NFL); tau phosphorylated at threonine 181 (p-tau), and NFL in cerebrospinal fluid (CSF); and one or more of PET with ¹⁸F-fluorodeoxyglucose, PET with amyloid tracers, and MRI. Cognitively healthy euploid controls aged up to 75 years who had no biomarker abnormalities were recruited from the Sant Pau Initiative on Neurodegeneration. We used a first-order locally estimated scatterplot smoothing curve to determine the order and age at onset of the biomarker changes, and the lowest ages at the divergence with 95% CIs are also reported where appropriate.

FINDINGS

Between Feb 1, 2013, and June 28, 2019 (Barcelona), and between June 1, 2009, and Dec 31, 2014 (Cambridge), we included 388 participants with Down syndrome (257 [66%] asymptomatic, 48 [12%] with prodromal Alzheimer's disease, and 83 [21%] with Alzheimer's disease dementia) and 242 euploid controls. CSF Aβ_1-42/1-40 and plasma NFL values changed in individuals with Down syndrome as early as the third decade of life, and amyloid PET uptake changed in the fourth decade. ¹⁸F-fluorodeoxyglucose PET and CSF p-tau changes occurred later in the fourth decade of life, followed by hippocampal atrophy and changes in cognition in the fifth decade of life. Prodromal Alzheimer's disease was diagnosed at a median age of 50·2 years (IQR 47·5-54·1), and Alzheimer's disease dementia at 53·7 years (49·5-57·2). Symptomatic Alzheimer's disease prevalence increased with age in individuals with Down syndrome, reaching 90-100% in the seventh decade of life.

INTERPRETATION

Alzheimer's disease in individuals with Down syndrome has a long preclinical phase in which biomarkers follow a predictable order of changes over more than two decades. The similarities with sporadic and autosomal dominant Alzheimer's disease and the prevalence of Down syndrome make this population a suitable target for Alzheimer's disease preventive treatments.

FUNDING

Instituto de Salud Carlos III, Fundació Bancaria La Caixa, Fundació La Marató de TV3, Medical Research Council, and National Institutes of Health.

Some Issues in Caring for People with the Dual Disability of Down's Syndrome and Alzheimer's Dementia

Virtually all individuals with Down's syndrome over the age of 35 years have neuropathological changes characteristic of Alzheimer's disease. It has become increasingly recognized that people with Down's syndrome and dementia have very special needs, and those who care for them require specialist knowledge and skills. This paper aims to explore some important issues in caring for persons with this dual disability. It commences with a brief outline on the prevalence of dementia in this population. Diagnostic issues and the clinical presentation of dementia in persons with Down's syndrome are reviewed. In an attempt to help staff respond to the opportunities and challenges they encounter, issues discussed include: promoting well-being, developing a shared vision on which to build practice, mealtimes – a therapeutic event, reality orientation and validation therapy, communication, activity and entertainment.

A Novel Framework to Measure Executive Function in Down Syndrome With Applications for Early Clinical Diagnosis of Dementia

Executive function (EF) decline is a consistent early sign of Alzheimer's disease (AD) among adults with Down syndrome (DS), which means that baseline measures of EF for individuals with DS are vital to allow detection of meaningful decline. We developed a framework to extract measures of three core components of EF (memory updating, inhibitory, and temporal components) within one task. Increases in memory load, inhibitory load, and temporal demands led to significant increases in reaction times and significant decreases in accuracy among 18 adults with DS and 18 typically developing matched individuals; thus, the expected effects of all three manipulations were detected. Good test-retest reliability indicated that this framework has the potential to provide a simple, baseline EF measure for individuals with DS.

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 Functioning in Children with Down Syndrome: Current Knowledge and Future Directions

Infants and children with Down syndrome (DS) can look forward toward bright futures, as individuals with DS are living healthier, more productive lives than ever due to medical advances, opportunities for early and continued intervention, and inclusive education. Despite these advances, infants and children with DS experience challenges in specific domains of cognitive functioning relative to their typically developing (TD) peers. Over the long term, individuals with DS are also more likely to develop Alzheimer's disease relative to the general population. Understanding cognitive functioning early in life may be important in charting cognitive decline over time. This chapter synthesizes the literature on cognitive functioning in infants and children with DS specific to general intelligence or IQ, language development, recall memory, and executive functioning, with additional focus on critical issues and future directions. These research findings provide important information for understanding cognitive competencies and intervention opportunities for children with DS and also serves to provide a foundation from which to plan longitudinal studies examining stability and change in cognitive functioning over time.

Aging With Down Syndrome: The Dual Diagnosis: Alzheimer's Disease and Down Syndrome

BACKGROUND

People with Down syndrome (DS) enjoy a longer life expectancy now than they ever have before and are therefore at greater risk of developing conditions associated with aging, including dementia.

OBJECTIVES

To explore the phenomenon of dementia in DS.

METHODS

Medline and Google Scholar searches were conducted for relevant articles, chapters, and books published until 2017. Search terms included Alzheimer's disease, cognitive impairment, dementia, DS, and trisomy 21. Publications found through this indexed search were reviewed for further references.

RESULTS AND CONCLUSIONS

Virtually, all subject aged 35 to 40 show key neuropathologic changes characteristic of Alzheimer's disease, but only a part of them show clinical signs of dementia, usually around the age of 50 years. Early signs of dementia in people with DS may be different from those experienced by the general population. Failure to recognize this can delay diagnosis and subsequent interventions.

Crystallized and fluid intelligence of university students with intellectual disability who are fully integrated versus those who studied in adapted enrichment courses

Background

Inclusion of people with intellectual disability (ID) in higher postsecondary academic education is on the rise. However, there are no scientific criteria for determining the eligibility for full inclusion of students with ID in university courses. This study focuses on two models of academic inclusion for students with ID: (a) separate adapted enrichment model: students with ID study in separate enrichment courses adapted to their level; (b) full inclusion model: students with ID are included in undergraduate courses, receive academic credits and are expected to accumulate the amount of credits for a B.A.

Aim

(a) To examine whether crystallized and fluid intelligence and cognitive tests can serve as screening tests for determining the appropriate placement of students with ID for the adapted enrichment model versus the full inclusion model. (b) To examine the attitudes towards the program of students with ID in the inclusion model.

Method/Procedure

The sample included 31 adults with ID: students with ID who were fully included (N = 10) and students with ID who participated in the adapted enrichment model (N = 21). Crystallized and fluid intelligence were examined (WAIS-III, Wechsler, 1997) and Hebrew abstract verbal tests (Glanz, 1989). Semi-structured interviews were conducted in order to examine the attitudes of students in the inclusion model towards the program.

Outcomes and results

The ANOVAs indicate that the most prominent difference between the groups was in vocabulary, knowledge and working memory. ROC analysis, a fundamental tool for diagnostic test evaluation, was used to determine the students’ eligibility for appropriate placement in the two models. Seven tests distinguished between the groups in terms of sensitivity and specificity. The interviews were analyzed according to three phases.

Conclusions/Implications

The results indicate that students with ID are able to participate in undergraduate courses and achieve academic goals. The general IQ and idioms test seem to be best determiners for appropriate placement of students with ID to one of the two models. The included students with ID are motivated and self-determined in continuing in the program.

Growth and Decline in Language and Phonological Memory Over Two Years Among Adolescents With Down Syndrome

Forty-two adolescents with Down syndrome (DS) ages 10 to 21 years completed a battery of language and phonological memory measures twice, 2 years apart. Individual differences were highly stable across two years. Receptive vocabulary scores improved, there was no change in receptive or expressive grammar scores, and nonword repetition scores declined. Digit memory and expressive vocabulary scores improved among younger adolescents, but generally held steady among older adolescents. These patterns may reveal key points in development at which interventions may be best applied. Further research is needed to understand specific processes in tasks that appear to be slowing or declining during adolescence. They may be important for understanding early aging and dementia in DS.

Memory profiles in Down syndrome across development: a review of memory abilities through the lifespan

Down syndrome (DS) is associated with a variety of cognitive impairments, notably memory impairments. Due to the high prevalence rates of early-onset dementia associated with DS, it is imperative to understand the comprehensive development of memory impairments beginning in childhood and into adulthood, as this may help researchers identify precursors of dementia at earlier stages of development and pinpoint targets for memory intervention. The current paper provides a systematic, developmentally focused review of the nature of memory difficulties in DS across the lifespan. Specifically, this review summarizes what is known about long-term, short-term, and working memory abilities (distinguishing between verbal and nonverbal modalities) in DS, compared to both mental age-matched typically developing peers and individuals with other forms of intellectual disability (ID) at three developmental stages (i.e., preschool, adolescence, and adulthood). Additionally, this review examines the degree of impairment reported relative to typically developing mental age-matched peers in the existing literature by examining effect size data across memory domains as a function of age. With few exceptions, memory abilities were impaired across the lifespan compared to mental age-matched typically developing peers. Relative to other groups with ID, research findings are mixed. Our review of the literature identified a scarcity of memory studies in early childhood, particularly for STM and WM. In adulthood, research was limited in the LTM and WM domains and very little research has compared memory abilities in older adults with DS to those with typical development. Looking to the future, longitudinal studies could provide a better understanding of the developmental trajectory of memory abilities in DS, and the possible associations between memory abilities and real-world functioning. This research could ultimately inform interventions to improve independence and overall quality of life for those with DS and their families.

Dendritic spine pathology and thrombospondin-1 deficits in Down syndrome

Abnormal dendritic spine structure and function is one of the most prominent features associated with neurodevelopmental disorders including Down syndrome (DS). Defects in both spine morphology and spine density may underlie alterations in neuronal and synaptic plasticity, ultimately affecting cognitive ability. Here we briefly examine the role of astrocytes in spine alterations and more specifically the involvement of astrocyte-secreted thrombospondin 1 (TSP-1) deficits in spine and synaptic pathology in DS.

Using the Optical Fractionator to Estimate Total Cell Numbers in the Normal and Abnormal Developing Human Forebrain

Human fetal brain development is a complex process which is vulnerable to disruption at many stages. Although histogenesis is well-documented, only a few studies have quantified cell numbers across normal human fetal brain growth. Due to the present lack of normative data it is difficult to gauge abnormal development. Furthermore, many studies of brain cell numbers have employed biased counting methods, whereas innovations in stereology during the past 20-30 years enable reliable and efficient estimates of cell numbers. However, estimates of cell volumes and densities in fetal brain samples are unreliable due to unpredictable shrinking artifacts, and the fragility of the fetal brain requires particular care in handling and processing. The optical fractionator design offers a direct and robust estimate of total cell numbers in the fetal brain with a minimum of handling of the tissue. Bearing this in mind, we have used the optical fractionator to quantify the growth of total cell numbers as a function of fetal age. We discovered a two-phased development in total cell numbers in the human fetal forebrain consisting of an initial steep rise in total cell numbers between 13 and 20 weeks of gestation, followed by a slower linear phase extending from mid-gestation to 40 weeks of gestation. Furthermore, we have demonstrated a reduced total cell number in the forebrain in fetuses with Down syndome at midgestation and in intrauterine growth-restricted fetuses during the third trimester.

Participation in recreation and cognitive activities as a predictor of cognitive performance of adults with/without Down syndrome

OBJECTIVE

The Cognitive Activity Theory suggests an association between participation in cognitive activities during midlife and cognitive functioning in the short term. We examined the impact of participation in cognitively stimulating activities conveyed during leisure activities on crystallized and fluid tests' performance among adults with intellectual disabilities (ID).

METHOD

Adults (n = 32; chronological age = 25-55) with non-specific ID and with Down syndrome rated the frequency of their participation in leisure activities. Pursuits included more cognitively involving (reading, participating in academic courses) and less cognitively involving (cooking, dancing) activities. Three judges ranked activities according to their cognitive load on a 1 (few cognitive components) to 5 (many cognitive components) points scale. The findings indicate two new scales: cognitively stimulating activities and recreational stimulating activities. The crystallized battery included phonemic fluency, synonyms, idioms, and verbal metaphors. The fluid battery included the Homophone Meaning Generation Test, Metaphoric Triad Test, Novel Metaphors Test, and Trail Making Test.

RESULTS

Hierarchal regression with chronological and mental age, recreational, and cognitively stimulating activities indicated that participation in recreational activities contributed significantly to the explained variance of word fluency. Participation in cognitive activities contributed significantly to the explained variance of most of the crystallized and fluid tests.

CONCLUSIONS

The findings support the Cognitive Activity Theory in populations with ID. The findings also support the Compensation Age Theory: not only endogenous factors (age, etiology, IQ level), but also exogenous factors such as life style determining the cognitive functioning of adults with ID. However, frequency and the cognitive load of the activities influenced their cognitive functioning.

An Exploratory Study Investigating How Adults with Intellectual Disabilities Perform on the Visual Association Test (VAT)

BACKGROUND

Neuropsychological tests of memory are believed to offer the greatest sensitivity at identifying people at the risk of developing dementia. There is a paucity of standardized and appropriate neuropsychological assessments of memory for adults with an intellectual disability. This study examines how adults with an intellectual disability perform on the Visual Association Test (VAT).

METHODS

Forty participants (18-45 years) with intellectual disability, without a diagnosis of dementia, completed the VAT and subtests of the CAMCOG-DS. Correlational analysis of the test variables was carried out.

RESULTS

All participants performed well on the VAT irrespective of age, gender or IQ. No significant correlations were found between the VAT and the subtests of the CAMCOG-DS.

CONCLUSIONS

The VAT was found to be an easy and quick test to use with people with intellectual disability and all participants scored above 'floor' level.

The subjective experience of individuals with Down syndrome living with dementia

An increasing number of studies have begun to explore the subjective experience of individuals with dementia. However, despite the increased prevalence of dementia in individuals with Down syndrome, no such published research has been undertaken within this population. The aim of this study was to explore the perspectives and subjective experiences of six individuals with Down syndrome and dementia. Semi-structured interview accounts were analysed using Interpretative Phenomenological Analysis, in order to gain a level of understanding concerning the impact of dementia upon respondents’ lives and sense of self. Five main themes emerged: (1) Self-image, (2) The Relational Self, (3) Making Sense of Decline,(4) Coping Strategies and (5) Emotional Experience. Whilst the process of adjusting to dementia appeared comparable to the general population, the content of this was influenced by multiple levels of context specific to having a concomitant intellectual disability.

Dementia in Down's syndrome

Down's syndrome is the most common genetic cause of learning difficulties, and individuals with this condition represent the largest group of people with dementia under the age of 50 years. Genetic drivers result in a high frequency of Alzheimer's pathology in these individuals, evident from neuroimaging, biomarker, and neuropathological findings, and a high incidence of cognitive decline and dementia. However, cognitive assessment is challenging, and diagnostic methods have not been fully validated for use in these patients; hence, early diagnosis remains difficult. Evidence regarding the benefits of cholinesterase inhibitors and other therapeutic options to treat or delay progressive cognitive decline or dementia is very scarce. Despite close similarities with late-onset Alzheimer's disease, individuals with Down's syndrome respond differently to treatment, and a targeted approach to drug development is thus necessary. Genetic and preclinical studies offer opportunities for treatment development, and potential therapies have been identified using these approaches.

Differentiating Aging Among Adults With Down Syndrome and Comorbid Dementia or Psychopathology

Differences were examined between three groups of adults with Down syndrome in their behavioral presentation, social life/activities, health, and support needs. We compared those with comorbid dementia, with comorbid psychopathology, and with no comorbid conditions. Adults with comorbid dementia were more likely to be older, have lower functional abilities, have worse health and more health conditions, and need more support in self-care. Adults with comorbid psychopathology were more likely to exhibit more behavior problems and to be living at home with their families. Adults with no comorbidities were most likely to be involved in community employment. Differences in behavioral presentation can help facilitate clinical diagnoses in aging in Down syndrome, and implications for differential diagnosis and service supports are discussed.

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.

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.

Validation of the Chinese version of the dementia screening questionnaire for individuals with intellectual disabilities (DSQIID-CV)

BACKGROUND

An increasing number of people with intellectual disabilities (ID) are at risk of developing age-related disorders such as dementia because of a dramatic increase in life expectancy in this population in the recent years. There is no validated dementia screening instrument for Chinese people with ID. The Dementia Screening Questionnaire for Individuals with Intellectual Disabilities (DSQIID) was reported to be a valid, user-friendly, easy-to-use observer-rated instrument. It was developed in the UK and has good psychometric properties. Validation of a Chinese version of the DSQIID will facilitate its application among the Chinese population.

METHOD

The DSQIID was translated into the Chinese version (DSQIID-CV). By purposive sampling, service users with ID aged 40 years or over were recruited through two large centres serving adults with ID in Hong Kong. Carers who had taken care of the participants continuously for the past 6 months were invited to complete the DSQIID-CV. All participants were examined by qualified psychiatrists to determine the presence or absence of dementia.

RESULTS

Two hundred people with ID whose age ranged between 40 and 73 years (mean 51 years, SD=7.34 years) were recruited to the study. A clinical diagnosis of dementia was established in 13 participants. An overall total score of 22 as a screening cut-off provided the optimum levels of specificity (0.995) and sensitivity (0.923). The DSQIID-CV showed good internal consistency (alpha=0.945) for all its 53 items, and excellent test-retest reliability (0.978, n=46) and inter-rater reliability (1.000, n=47). Exploratory factor analysis resulted in a four-factor solution explaining 45% of the total variance.

CONCLUSIONS

The DSQIID-CV is shown to have robust psychometric properties. It is the first valid and reliable dementia screening instrument for Chinese adults with ID.

The association between behavioural and emotional problems and age in adults with Down syndrome without dementia: Examining a wide spectrum of behavioural and emotional problems

The literature on the association between behavioural and emotional problems and ageing in adults with Down syndrome (DS) without dementia is limited and has generally not reported on a wide range of behavioural and emotional problems. This research aimed to extend the field by examining the associations between age and a wide spectrum of behavioural and emotional problems in adults with DS without dementia. A preliminary analysis of the association between potential covariates and behavioural and emotional problems was also undertaken. Parents and caregivers completed a questionnaire on behavioural and emotional problems for 53 adults with DS aged between 16 and 56 years. Twenty-eight adults with DS and their caregivers were part of a longitudinal sample, which provided two time points of data approximately four years apart. Additionally, 25 participants with DS and their caregivers were from a cross sectional sample, which provided one time point of data. Random effects regression analyses were used to examine the patterns in item scores for behavioural and emotional problems associated with age. No significant associations between age and the range or severity of any behavioural and emotional items were found. This suggested a more positive pattern for ageing adults with DS than has been previously described. Given that behavioural and emotional problems were not associated with age, investigation into other factors that may be associated with the behavioural and emotional difficulties for adults with DS is discussed.

A five year follow-up study of dementia in persons with Down's syndrome: early symptoms and patterns of deterioration

Objectives: To investigate the development of dementia over a five year follow up period in a population of females with Down's syndrome; to examine age at onset and duration of dementia in the population; to document the clinical features of dementia and to highlight scores on functional and cognitive rating scales at diagnosis of dementia and at the onset of complete dependency.

Method: A five year follow-up study of 80 female subjects on prevalence of dementia, early clinical features of dementia and patterns of scoring on rating scales at diagnosis and end-stage dementia was completed. Results: Over the five year study period the number of subjects diagnosed with dementia rose from seven (8.75%) to 35 (43.75%). Age related prevalence figures showed that dementia was more common with increasing age. The earliest recognisable symptoms of dementia were memory loss, spatial disorientation and loss of independence especially in the area of personal hygiene. These findings were confirmed by the rating scales used in the study.

Conclusions: The earliest recognisable clinical features of dementia include memory loss and increased dependency. The results of this study should facilitate earlier diagnosis of dementia in DS.

Long-term impact of parental well-being on adult outcomes and dementia status in individuals with Down syndrome

Parental characteristics were significant predictors of health, functional abilities, and behavior problems in adults with Down syndrome (n  =  75) over a 22-year time span, controlling for initial levels and earlier changes in these outcomes. Lower levels of behavior problems were predicted by improvements in maternal depressive symptoms. Higher levels of functional abilities were predicted by prior measures of and improvements in maternal depressive symptoms. Better health was predicted by prior measures of maternal depressive symptoms, paternal positive psychological well-being, relationship quality between fathers and their adult children, and improvements in maternal positive psychological well-being. Dementia status was also predicted by parental characteristics. The study suggests the importance of the family context for healthy aging in adults with Down syndrome.

Vision deficits in adults with Down syndrome

BACKGROUND

In individuals with Down syndrome, virtually all structures of the eye have some abnormality, which likely diminishes vision. We examined basic vision functions in adults with Down syndrome.

MATERIALS AND METHODS

Participants completed a battery of psychophysical tests that probed a comprehensive array of visual functions. The performance of adults with Down syndrome was compared with younger and older adults without intellectual disability.

RESULTS

Adults with Down syndrome had significant vision deficits, reduced sensitivity across spatial frequencies and temporal modulation rates, reduced stereopsis, impaired vernier acuity and anomalies in colour discrimination. The pattern of deficits observed was similar to those seen by researchers examining adults with Alzheimer's disease.

CONCLUSIONS

Our findings suggest that a common mechanism may be responsible for the pattern of deficits observed, possibly the presence of Alzheimer's disease neuropathology in the visual association cortex. We also showed that individuals with mild to moderate intellectual disability are capable of participating in studies employing state-of-the-art psychophysical procedures. This has wider implications in terms of their ability to participate in research that use similar techniques.

Cognitive development and Down syndrome: age-related change on the Stanford-Binet test (fourth edition)

Growth models for subtests of the Stanford-Binet Intelligence Scale, 4th edition ( R. L. Thorndike, E. P. Hagen, & J. M. Sattler, 1986a , 1986b ) were developed for individuals with Down syndrome. Models were based on the assessments of 208 individuals who participated in longitudinal and cross-sectional research between 1987 and 2004. Variation in performance among individuals was large and significant across all subtests except Memory for Sentences. Scores on the Memory for Sentences subtest remained low between ages 4 to 30 years. Greatest variation was found on the Pattern Analysis subtest, where scores continued to rise into adulthood. Turning points for scores on the Vocabulary and Comprehension subtests appeared premature relative to normative patterns of development. The authors discuss development at the subdomain level and analyze both individual and group trajectories.

A validity study of the Working Group's Orientation Test for individuals with moderate to severe intellectual disability

BACKGROUND

Decline in orientation skill has been reported as an early indicator of Dementia of Alzheimer's Type (DAT). Orientation subtest of the Working Group's Test Battery was examined whether this test is useful to identify DAT patients among adults with moderate to severe ID.

METHODS

Sixteen DAT patients and 35 non-demented normal controls with moderate to severe ID were followed for a year using Orientation Test. The scores on the baseline evaluation and the longitudinal changes over a 1-year period among the DAT patients and the normal controls were compared. The effects of age and etiologies of ID on the performance of Orientation were also examined.

RESULTS

The DAT group's score was significantly poorer than that of the normal control group on the baseline evaluation. The score changes over the 1-year period were not significantly different between the groups. However, there was a considerable overlap between the score distributions of the two groups. The effects of age and etiologies of ID on the performance of Orientation were not significant.

CONCLUSIONS

Screening DAT patients based only on the score of the Orientation Test of the Working Group's Test Battery may produce a large number of diagnostic errors.

Selective Attention Deficits Associated With Mild Cognitive Impairment and Early Stage Alzheimer's Disease in Adults With Down Syndrome

Adults with Down syndrome and early stage Alzheimer's disease showed decline in their ability to selectively attend to stimuli in a multitrial cancellation task. They also showed variability in their performance over the test trials, whereas healthy participants showed stability. These changes in performance were observed approximately 2 years prior to a physician's diagnosis of possible Alzheimer's disease, which was made when they were exhibiting declines in episodic memory suggestive of mild cognitive impairment. Performance on this task varied with the evolution of dementia, showed modestly good sensitivity and specificity, and was relatively easy to administer. Given these qualities this task could be a valuable addition to a neuropsychological battery intended for the assessment of mild cognitive impairment and Alzheimer's disease in adults with Down syndrome.

Successful aging in a 70-year-old man with down syndrome: a case study

The authors present a case study of a 70-year-old man with Down syndrome ("Mr. C.") who they followed for 16 years and who does not exhibit declines in cognitive or functional capacities indicative of dementia, despite having well-documented, complete trisomy 21. The authors describe the age-associated changes that occurred over 16 years as well as provide detailed information regarding Mr. C.'s health and genetic status. To further emphasize Mr. C.'s successful aging, the authors compared his longitudinal performance profile with that of 2 peers of comparable level of intellectual functioning: 1 similar-aged man with clinical Alzheimer's disease and a younger man who was healthy. The authors present potential explanations for the phenotypic variability observed in individuals with Down syndrome.

Alzheimer's disease in Down syndrome: neurobiology and risk

Down syndrome (DS) is characterized by increased mortality rates, both during early and later stages of life, and age-specific mortality risk remains higher in adults with DS compared with the overall population of people with mental retardation and with typically developing populations. Causes of increased mortality rates early in life are primarily due to the increased incidence of congenital heart disease and leukemia, while causes of higher mortality rates later in life may be due to a number of factors, two of which are an increased risk for Alzheimer's disease (AD) and an apparent tendency toward premature aging. In this article, we describe the increase in lifespan for people with DS that has occurred over the past 100 years, as well as advances in the understanding of the occurrence of AD in adults with DS. Aspects of the neurobiology of AD, including the role of amyloid, oxidative stress, Cu/ZN dismutase (SOD-1), as well as advances in neuroimaging are presented. The function of risk factors in the observed heterogeneity in the expression of AD dementia in adults with DS, as well as the need for sensitive and specific biomarkers of the clinical and pathological progressing of AD in adults with DS is considered.

Altered expression of KIF17, a kinesin motor protein associated with NR2B trafficking, may mediate learning deficits in a Down syndrome mouse model

OBJECTIVE

Down syndrome (DS), a major cause of mental retardation, affects 1 of 800 newborns. Mouse models for Down syndrome have been studied and found to have developmental and learning deficits, including the Ts65Dn (DS) mouse model. N-methyl-D-aspartate receptor NR2B subunit enhances synaptic plasticity. The up-regulation of KIF17, a motor protein that transports NR2B to the synaptic region parallels up-regulation of synaptic NR2B. Down regulation of KIF17 reflects up-regulation of less plastic NR2A subunit. We evaluated NR2B, NR2A, and KIF17 in Ts65Dn and control mice.

STUDY DESIGN

Ts65Dn (4) and control (4) adult brains were collected; NR2A, NR2B, and KIF17 were measured by Western blot and quantified using National Institutes of Health Image software. Comparisons were made using analysis of variance, < .05 was considered significant.

RESULTS

There was a significant decrease in KIF17 (P = .04) level in Ts65Dn mice as compared with the control animals, but there were no significant differences in the levels of NR2A (P = .79) and NR2B (P = .96).

CONCLUSION

The significant decrease of KIF17 inTs65Dn animals may in part mediate cognitive defects in DS.

Down syndrome: caring holistically in primary health care

All primary health care should be underpinned with a firm theoretical knowledge. The holistic management of Down syndrome patients should be an integral part of this knowledge base. The application of this knowledge should ideally encompass a positive approach to empowering patients to lead healthy, active and normal lives. This article highlights a basic documentation of what 'Down syndrome' is. The article gives community nursing staff the opportunity to refresh their knowledge of the condition, then encourages critical reflection on professional practice within primary care, with the intention of raising skill and awareness for the holistic management of patients with Down syndrome.

Fifteen-year follow-up of 92 hospitalized adults with Down's syndrome: incidence of cognitive decline, its relationship to age and neuropathology

BACKGROUND

The clinical and neuropathological features associated with dementia in Down's syndrome (DS) are not well established. Aims To examine clinico-pathological correlations and the incidence of cognitive decline in a cohort of adults with DS.

METHOD

A total of 92 hospitalized persons with DS were followed up from 1985 to December 2000. At outset, 87 participants were dementia-free, with a median age of 38 years. Assessments included the Prudhoe Cognitive Function Test (PCFT) and the Adaptive Behavior Scale (ABS), to measure cognitive and behavioural deterioration. Dementia was diagnosed from case records and caregivers' reports.

RESULTS

Eighteen (21%) patients developed dementia during follow-up, with a median age of onset 55.5 years (range 45-74). The PCFT demonstrated cognitive decline among those with a less severe intellectual disability (mild and moderate) but not among the profoundly disabled people (severe and profound). Clinical dementia was associated with neuropathological features of Alzheimer's disease, and correlated with neocortical neurofibrillary tangle densities. At the age of 60 years and above, a little more than 50% of patients still alive had clinical evidence of dementia.

CONCLUSIONS

Clinical dementia associated with measurable cognitive and functional decline is frequent in people with DS after middle age, and can be readily diagnosed among less severely intellectually disabled persons using measures of cognitive function such as the PCFT and behavioural scales such as the ABS. In the more profoundly disabled people, the diagnosis of dementia is facilitated by the use of behavioural and neurological criteria. In this study, the largest prospective DS series including neuropathology on deceased patients, the density of neurofibrillary tangles related more closely to the dementia of DS than senile plaques. In people with DS surviving to middle and old age, the development of dementia of Alzheimer type is frequent but not inevitable, and some people with DS reach old age without clinical features of dementia.

A preliminary study of the validity of memory tests recommended by the Working Group for individuals with moderate to severe intellectual disability

BACKGROUND

Normal aging and Dementia of Alzheimer's Type (DAT) among higher functioning individuals with intellectual disability (ID) have been relatively well studied using a variety of cognitive tests. However, cognitive studies for lower functioning individuals with ID are scarce in the literature. The Working Group recommended the Test Battery for the Diagnosis of Dementia in Individuals with various level of ID. Few studies have investigated whether the Test Battery is useful to study dementia among individuals with moderate to severe ID. The purpose of this study is to investigate whether the memory subtests of the Test Battery are useful for measuring memory function and studying DAT in individuals with moderate to severe ID.

METHODS

We compared performances on the memory subtests in the Test Battery between 31 normal controls and 13 DAT patients with moderate to severe ID. Performance on the Picture Recognition Test was also compared between five normal controls and five DAT patients. This test was designed by our team to measure memory functions of individuals with moderate to severe ID.

RESULTS

Among the memory subtests of the Test Battery, the Autobiographical Memory and the Orientation were found to be useful for studying normal and abnormal aging among individuals with moderate to severe ID. Preliminary data for the Picture Recognition Test demonstrated that these individuals properly responded to this test and the majority of DAT patients could be differentiated from the normal controls based on their performance.

CONCLUSIONS

Further studies are necessary to improve usefulness of the memory subtests of the Test Battery for lower functioning individuals with ID. While the results suggest that the Picture Recognition Test may be more effective in discriminating individuals with DAT, given the very small sample sizes, a study with larger sample sizes should be undertaken to validate these findings.

Neuropsychiatric and behavioral aspects of trisomy 21

Down syndrome (DS), or trisomy 21, is the most common identifiable genetic cause of mental retardation. The syndrome is unique with respect to its cognitive, behavioral, and psychiatric profiles. The well-known cheerful and friendly demeanor often creates a personality stereotype, with parents and observers commenting on the positive attributes. Despite these strengths, approximately 20% to 40% of children with DS have recognized behavioral problems. Such problems persist through adulthood, with a decrease in externalizing symptoms of aggressiveness and attention problems and the emergence of internalizing symptoms of depression and loneliness. In adulthood, the presence of early-onset dementia of the Alzheimer type and cognitive decline may pose a challenge in recognizing these internalizing symptoms. Understanding the age-related changes in cognitive functioning and behavioral profiles in individuals with DS provides insight into clinical and treatment implications.

Dementia and mortality in persons with Down's syndrome

BACKGROUND

Numerous studies have documented that persons with Down's syndrome (DS) are at an increased risk of Alzheimer's disease (AD). However, at present it is still not clear whether or not all persons with DS will develop dementia as they reach old age.

METHODS

We studied 506 people with DS, aged 45 years and above. A standardized assessment of cognitive, functional and physical status was repeated annually. If deterioration occurred, the patients were examined and the differential diagnosis of dementia was made according to the revised Dutch consensus protocol and according to the ICD-10 Symptom Checklist for Mental Disorders. We compared our findings with those reported in the literature.

RESULTS

The overall prevalence of dementia was 16.8%. Up to the age of 60, the prevalence of dementia doubled with each 5-year interval. Up to the age of 49, the prevalence is 8.9%, from 50 to 54, it is 17.7%, and from 55 to 59, it is 32.1%. In the age category of 60 and above, there is a small decrease in prevalence of dementia to 25.6%. The lack of increase after the age of 60 may be explained by the increased mortality among elderly demented DS patients (44.4%) in comparison with non-demented patients (10.7%) who we observed during a 3.3-year follow-up. There was no decrease in incidence of dementia in the age group of 60 and above. Our findings are very similar to those published in the literature. Patients with dementia were more frequently treated with antiepileptic, antipsychotic and antidepressant drugs. The history of depression was strongly associated with dementia.

CONCLUSIONS

Our study is one of the largest population-based studies to date. We found that despite the exponential increase in prevalence with age, the prevalence of dementia in the oldest persons with DS was not higher than 25.6%.

Vision and oral health needs of individuals with intellectual disability

Over the past 20 years, there has been an increased emphasis on health promotion, including prevention activities related to vision and oral health, for the general population, but not for individuals with intellectual disability (ID). This review explores what is known about the prevalence of vision problems and oral health conditions among individuals with ID, presents a rationale for the increased prevalence of these conditions in the context of service utilization, and examines the limitations of the available research. Available data reveal a wide range of prevalence estimates for vision problems and oral health conditions, but all suggest that these conditions are more prevalent among individuals with ID compared with the general population, and disparities exist in the receipt of preventive and early treatment for these conditions for individuals with ID. Recommendations for health improvement in these areas include better health planning and monitoring through standardized population-based data collection and reporting and increased emphasis on health promotion activities and early treatment in the healthcare system.

Trisomy 21: From Chromosomes to Mental Retardation

The first descriptions of the trisomy 21 phenotype were by Jean-Etienne-Dominique Esquirol (1838), Edouard Séguin (1846) and later by John L. H. Down in 1862. It took more than a century to discover the extra-chromosomal origin of the syndrome commonly called "Down's syndrome" and which, we suggest, should be referred to as "Trisomy 21". In this review we are presenting the landmarks, from the pioneering description of the syndrome in 1838 to Jérôme Lejeune's discovery of the first genetic substrate for mental retardation. The sequencing of HSA21 was a new starting point that generated transcriptome studies, and we have noted that studies of gene over-expression have provided the impetus for discovering the HSA21 genes associated with trisomy 21 cognitive impairment.

Dementia of the Alzheimer's type and accelerated aging in Down syndrome

This case study, of a woman with Down syndrome and dementia of the Alzheimer's type (DAT), follows the course of her decline over an 11-year period until death at age 57. Detailed neuropathological findings are also presented. This case illustrates features of premature aging that are typically associated with Down syndrome, and the progressive changes in memory and cognition that are usually associated with DAT. Although the subject's cardiovascular condition and thyroid disorder were treated, they may have contributed to the decline of her memory. This case shows the difficulty in diagnosing dementia in an individual with mental retardation who suffered comorbid episodes of depression and psychosis.