Six Weeks to 45 Years: A Longitudinal Study of a Population with Down Syndrome

Vocabulary and expressive morpho-syntax in individuals with Down syndrome: Links to narration

BACKGROUND

Narrative ability is crucial for social participation in everyday and school life but involves different language abilities such as vocabulary and morpho-syntax. This is particularly difficult for individuals who display both language and cognitive impairments. Previous research has identified productive vocabulary as a possible key factor for narrative performance in individuals with Down syndrome. Considering a close connection between lexical and morpho-syntactic performance within language acquisition and the distinct impairments that individuals with Down syndrome display concerning their morpho-syntactic skills, the nature of a relation between vocabulary and narrative skills under the influence of grammatical deficits requires further investigation.

METHODS

Narrations were obtained from 28 children and adolescents with Down syndrome (aged 10;0-20;1) using a non-verbal picture book. Narrative abilities were rated using the Narrative Scoring Scheme across seven narrative aspects (including macro- and microstructure). Vocabulary analyses and morpho-lexical context analyses including verb and conjunction enumerations, evaluation of verb position and MLU were conducted. Findings from the transcript analysis have been supplemented with data from standardized language measures evaluating expressive lexical and morpho-syntactic development. A multiple regression analysis was conducted to identify significant predictors for narrative outcome in the participants with Down syndrome.

RESULTS

Lexical analyses revealed a high heterogeneity in production of subordinating conjunctions as a link between lexical and morpho-syntactic abilities. Comparisons of standardized and narrative data demonstrated differences in subordinate clause production depending on the elicitation setting. A multiple regression analysis identified the number of different verbs in the narrative task as the most significant predictor for narrative performance in individuals with Down syndrome.

DISCUSSION AND IMPLICATIONS

The findings of this study contribute to the knowledge regarding factors that influence narrative performance in individuals with language impairment. A differentiated verb lexicon can be identified as the key ability for reaching advanced narrative skills in participants with Down syndrome. These findings are of clinical relevance for therapeutic and educational support and contribute to an understanding of the relation between strengths in vocabulary and morpho-syntactic weaknesses in individuals with Down syndrome within communicative participation.

Psychomotor development in infants and young children with Down syndrome-A prospective, repeated measure, post-hoc analysis

Children with Down syndrome (DS) show delayed acquisition of cognitive and functional skills compared to typically developing children. The objective of this study was to accurately describe early development of infants and young children (children hereafter) with DS based on a large recent sample. We carried out repeated measure analysis of the global development quotient (GDQ) and developmental age using data from the Assessment of Systematic Treatment with Folinic Acid and Thyroid Hormone on Psychomotor Development of Down Syndrome Young Children (ACTHYF) study (NCT01576705). Because there was no statistically significant difference in the primary endpoint between active treatment and placebo, data from all treatment groups were pooled for post-hoc analysis. Data of 141 children with DS aged 6-18 months at inclusion were analyzed. Mean GDQ decreased over the study period, especially in the youngest age classes ([6-9] and [9-12] months), indicating that acquisition of skills occurred at a slower pace compared to typically developing children. Strongest deficits were observed for motor and hearing and language skills. Only GDQ at baseline correlated significantly with evolution of GDQ. Future studies should aim at elucidating the mechanisms underlying motor and language development. Early pharmacological interventions together with early childhood therapies might be necessary to improve the developmental trajectory of children with DS.

Characterizing the Richness of Maternal Input for Word Learning in Neurogenetic Disorders

Promoting language abilities, including early word learning, in children with neurogenetic disorders with associated language disorders, such as Down syndrome (DS) and fragile X syndrome (FXS), is a main concern for caregivers and clinicians. For typically developing children, the quality and quantity of maternal language input and maternal gesture use contributes to child word learning, and a similar relation is likely present in DS and FXS. However, few studies have examined the combined effect of maternal language input and maternal gesture use on child word learning. We present a multidimensional approach for coding word-referent transparency in naturally occurring input to children with neurogenetic disorders. We conceptualize high-quality input from a multidimensional perspective, considering features from linguistic, interactive, and conceptual dimensions simultaneously. Using case examples, we highlight how infrequent the moments of word-referent transparency are for three toddlers with DS during play with their mothers. We discuss the implications of this multidimensional framework for children with DS and FXS, including the clinical application of our approach to promote early word learning for these children.

Auditory-Perceptual Features of Speech in Children and Adults With Down Syndrome: A Speech Profile Analysis

Purpose The aim of this study was to determine how the speech disorder profiles in Down syndrome (DS) relate to reduced intelligibility, atypical overall quality, and impairments in the subsystems of speech production (phonation, articulation, resonance, and prosody). Method Auditory-perceptual ratings of intelligibility, overall quality, and features associated with the subsystems of speech production were obtained from recordings of 79 children and adults with DS. Ratings were made for sustained vowels (62 of 79 speakers) and short sentences (79 speakers). The data were analyzed to determine the severity of the affected features in each speaking task and to detect patterns in the group data by means of principal components analysis. Results Reduced intelligibility was noted in 90% of the speakers, and atypical overall speech quality was noted in 100%. Affected speech features were distributed across the speech production subsystems. Principal components analysis revealed four components each for the vowel and sentence tasks, showing that individuals with DS are not homogeneous in the features of their speech disorder. Discussion The speech disorder in DS is complex in its perceptual features and reflects impairments across the subsystems of speech production, but the pattern is not uniform across individuals, indicating that attention must be given to individual variation in designing treatments.

Intervención temprana en Síndrome de Down: Una revisión sistemática

Introducción: El síndrome de Down presenta importantes diferencias en tasas de incidencia según territorios y países, siendo además una de los trastornos genéticos más complejos, aunque su detección sea la más precoz de los trastornos genéticos. En España se ha producido una drástica reducción de nacimientos, existiendo un aumento en otras zonas del mundo como Latinoamérica. Objetivo y método: Se pretende realizar una revisión sistemática sobre el conocimiento científico actual relacionado con intervenciones tempranas en SD desde los años 2000 al 2017, utilizando la metodología PRISMA. Resultados: Se observa intensas lagunas metodológicas, enfatizándose las investigaciones transversales por encima de los longitudinales y sobre todo en zonas concretas del mundo. De este síndrome siguen interesando los factores cognitivos en detrimento de variables familiares y otros aspectos claves para un desarrollo psicoevolutivo adecuado. No se observan trabajos de intervención temprana ni de evaluación de programas en países hispanohablantes, y la mayoría de publicaciones científicas mezclan edades y sexos en sus muestras. Discusión: Se discuten los resultados obtenidos de la revisión realizada. Conclusiones: A lo largo del tiempo se observa una importante reducción del interés científico por este síndrome. Se siguen realizando trabajos de manera redundante sobre los mismos aspectos, sin valorar subdimensiones imprescindibles para el desarrollo biopsicosocial de este colectivo.

Relations between Everyday Executive Functioning and Language in Youth with Down Syndrome and Youth with Autism Spectrum Disorder

Language and executive functioning are major impairments in many neurodevelopmental disorders, but little is known about the relations between these constructs, particularly using parent-report. Thus, the current research sought to examine relations between executive function and language in two groups - Down syndrome (DS; n=41; Mage = 11.2) and autism spectrum disorder (ASD; n=91; Mage = 7.7). Results were as follows: in DS, executive function predicted pragmatic, but not structural language after covarying for age, sex, and social functioning; in ASD, executive function predicted both. Findings highlight the interrelatedness of language and executive functioning and may have implications for intervention development.

A comprehensive examination of the memory profile of youth with Down syndrome in comparison to typically developing peers

Down syndrome (DS) is associated with significant memory deficits beyond overall global cognitive impairment. Although a number of studies have examined memory abilities in adults and teens with DS, very few studies have examined memory abilities in children with DS. Additionally, research has yet to examine prospective memory (i.e., remembering to carry out an action in the future) in youth with DS. Consequently, the current study aimed to comprehensively examine the memory profile, including learning, immediate recall, delayed recall and prospective memory, of youth with DS (n = 22, age M = 11.43) in comparison to typically developing, mental-age (MA) matched children (n = 20, age M = 5.04) Consistent with past research, the results indicated that youth with DS performed significantly below MA-expectations on tasks of immediate verbal recall, learning across trials, and prospective memory, and there was a trend toward youth with DS performing below MA-expectations on delayed recall tasks. However, youth with DS did not differ significantly from MA-matched peers on immediate visual recall, rate of learning across trials, or proportion of items recalled on verbal and visual memory tasks following a delay (i.e., proportion relative to their own recall performance prior to the delay). These results highlight the relative strengths and challenges experienced by youth with DS on different learning and memory tasks. The implications of these findings for educators and caregivers are discussed.

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.

Speech and motor speech disorders and intelligibility in adolescents with Down syndrome

The goal of this research was to assess the support for motor speech disorders as explanatory constructs to guide research and treatment of reduced intelligibility in persons with Down syndrome (DS). Participants were the 45 adolescents with DS in the prior paper who were classified into five mutually-exclusive motor speech classifications using the Speech Disorders Classification System. An ordinal index classified participants' percentage of intelligible words in conversation as High (≥ 85%), Moderate (80% - 84.9%), or Low (< 80%). Statistical analyses tested for significant differences in intelligibility status associated with demographic, intelligence, and language variables, and intelligibility status associated with motor speech classifications and speech, prosody, and voice variables. For the 10 participants who met criteria for concurrent Childhood Dysarthria and Childhood Apraxia of Speech at assessment, 80% had reduced (Moderate or Low) intelligibility and 20% had High intelligibility (significant effect size: 0.644). Proportionally more of the 32 participants who met criteria for either dysarthria or apraxia had reduced intelligibility (significant effect size: 0.318). Low intelligibility was significantly associated with across-the-board reductions in phonemic and phonetic accuracy and with inappropriate prosody and voice. Findings are interpreted as support for motor speech disorders in adolescents with DS as explanatory constructs for their reduced intelligibility. Pending cross-validation of findings in diverse samples of persons with DS, studies are needed to assess the efficacy of motor speech classification status to guide selection of treatment methods and intelligibility targets. Abbreviations: CAS: Childhood Apraxia of Speech; CD: Childhood Dysarthria; DS: Down syndrome; II: Intelligibility Index; No MSD: No Motor Speech Disorder; OII: Ordinal Intelligibility Index; PSD: Persistent Speech Delay; SDCS: Speech Disorders Classification System; SMD: Speech Motor Delay.

Brief Report: Contrasting Profiles of Everyday Executive Functioning in Smith-Magenis Syndrome and Down Syndrome

Everyday executive function (EF) was examined in Smith-Magenis syndrome (SMS), associated with high risk of behaviour disorder, and Down syndrome (DS), associated with relatively low risk of behaviour disorder. Caregivers of 13 children with SMS and 17 with DS rated everyday EF using the Behavioral Rating Inventory of Executive Functioning-Preschool. Greater everyday EF deficits relative to adaptive ability were evident in SMS than in DS. The SMS profile of everyday EF abilities was relatively uniform; in DS emotional control strengths and working memory weaknesses were evident. Findings implicate broad everyday EF difficulties in SMS compared to DS, corresponding with increased rates of behaviour disorder in SMS. Findings further suggest that everyday EF profiles may, in part, be syndrome related.

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.

Differential Brain, Cognitive and Motor Profiles Associated with Partial Trisomy. Modeling Down Syndrome in Mice

We hypothesize that the trisomy 21 (Down syndrome) is the additive and interactive outcome of the triple copy of different regions of HSA21. Because of the small number of patients with partial trisomy 21, we addressed the question in the Mouse in which three chromosomal regions located on MMU10, MMU17 and MMU16 carries almost all the HSA21 homologs. Male mice from four segmental trisomic strains covering the D21S17-ETS2 (syntenic to MMU16) were examined with an exhaustive battery of cognitive tests, motor tasks and MRI and compared with TS65Dn that encompasses D21S17-ETS2. None of the four strains gather all the impairments (measured by the effect size) of TS65Dn strain. The 152F7 strain was close to TS65Dn for motor behavior and reference memory and the three other strains 230E8, 141G6 and 285E6 for working memory. Episodic memory was impaired only in strain 285E6. The hippocampus and cerebellum reduced sizes that were seen in all the strains indicate that trisomy 21 is not only a hippocampus syndrome but that it results from abnormal interactions between the two structures.

Improving Memory and Cognition in Individuals with Down Syndrome

Down syndrome (DS), often due to trisomy 21, is the most common genetic cause of intellectual disability (ID). In addition, virtually all individuals with DS develop the neuropathology of Alzheimer's disease (AD) by the age of 40 years and almost 60 % will manifest symptoms of AD dementia by the age of 65 years. Currently, there are no pharmacological treatments available for ID in individuals with DS and only limited symptomatic treatments for AD dementia. Advances in our understanding in both the molecular basis of ID and the pathogenesis of AD have created opportunities to study potential therapeutic targets. Recent studies in animal models of DS continue to provide a rational basis for translating specific compounds into human clinical trials. However, target and compound selection are only initial steps in the drug development pathway. Other necessary considerations include appropriate study designs to assess efficacy in the DS population, as well as operational aspects specifically tailored to assess cognition in this population. We discuss recent progress in the development of compounds for both ID and AD in individuals with DS, as well as concepts for the design and conduct of clinical trials with such compounds.

Assessment of Cognitive Scales to Examine Memory, Executive Function and Language in Individuals with Down Syndrome: Implications of a 6-month Observational Study

Down syndrome (DS) is the most commonly identifiable genetic form of intellectual disability. Individuals with DS have considerable deficits in intellectual functioning (i.e., low intellectual quotient, delayed learning and/or impaired language development) and adaptive behavior. Previous pharmacological studies in this population have been limited by a lack of appropriate endpoints that accurately measured change in cognitive and functional abilities. Therefore, the current longitudinal observational study assessed the suitability and reliability of existing cognitive scales to determine which tools would be the most effective in future interventional clinical studies. Subtests of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Cambridge Neuropsychological Test Automated Battery (CANTAB), and Clinical Evaluation of Language Fundamentals-Preschool-2 (CELF-P-2), and the Observer Memory Questionnaire-Parent Form (OMQ-PF), Behavior Rating Inventory of Executive Function®-Preschool Version (BRIEF-P) and Leiter International Performance Scale-Revised were assessed. The results reported here have contributed to the optimization of trial design and endpoint selection for the Phase 2 study of a new selective negative allosteric modulator of the GABAA receptor α5-subtype (Basmisanil), and can be applied to other studies in the DS population.

Everyday executive functions in Down syndrome from early childhood to young adulthood: evidence for both unique and shared characteristics compared to youth with sex chromosome trisomy (XXX and XXY)

Executive functions (EF) are thought to be impaired in Down syndrome (DS) and sex chromosome trisomy (Klinefelter and Trisomy X syndromes; +1X). However, the syndromic specificity and developmental trajectories associated with EF difficulties in these groups are poorly understood. The current investigation (a) compared everyday EF difficulties in youth with DS, +1X, and typical development (TD); and (b) examined relations between age and EF difficulties in these two groups and a TD control group cross-sectionally. Study 1 investigated the syndromic specificity of EF profiles on the Behavior Rating Inventory of Executive Function (BRIEF) in DS (n = 30), +1X (n = 30), and a TD group (n = 30), ages 5–18 years. Study 2 examined age effects on EF in the same cross-sectional sample of participants included in Study 1. Study 3 sought to replicate Study 2's findings for DS by examining age-EF relations in a large independent sample of youth with DS (n = 85) and TD (n = 43), ages 4–24 years. Study 1 found evidence for both unique and shared EF impairments for the DS and +1X groups. Most notably, youth with +1X had relatively uniform EF impairments on the BRIEF scales, while the DS group showed an uneven BRIEF profile with relative strengths and weaknesses. Studies 2 and 3 provided support for fairly similar age-EF relations in the DS and TD groups. In contrast, for the +1X group, findings were mixed; 6 BRIEF scales showed similar age-EF relations to the TD group and 2 showed greater EF difficulties at older ages for +1X. These findings will be discussed within the context of efforts to identify syndrome specific cognitive-behavioral profiles for youth with different genetic syndromes in order to inform basic science investigations into the etiology of EF difficulties in these groups and to develop treatment approaches that are tailored to the needs of these groups.

Stability of cognitive performance in children with mild intellectual disability

AIM

Longitudinal studies that have examined cognitive performance in children with intellectual disability more than twice over the course of their development are scarce. We assessed population and individual stability of cognitive performance in a clinical sample of children with borderline to mild non-syndromic intellectual disability.

METHOD

Thirty-six children (28 males, eight females; age range 3-19y) with borderline to mild intellectual disability (Full-scale IQ [FSIQ] 50-85) of unknown origin were examined in a retrospective clinical case series using linear mixed models including at least three assessments with standardized intelligence tests.

RESULTS

Average cognitive performance remained remarkably stable over time (high population stability, drop of only 0.38 IQ points per year, standard error=0.39, p=0.325) whereas individual stability was at best moderate (intraclass correlation of 0.58), indicating that about 60% of the residual variation in FSIQ scores can be attributed to between-child variability. Neither sex nor socio-economic status had a statistically significant impact on FSIQ.

INTERPRETATION

Although intellectual disability during childhood is a relatively stable phenomenon, individual stability of IQ is only moderate, likely to be caused by test-to-test reliability (e.g. level of child's cooperation, motivation, and attention). Therefore, clinical decisions and predictions should not rely on single IQ assessments, but should also consider adaptive functioning and previous developmental history.

Ageing and dementia in a longitudinal study of a cohort with Down syndrome

BACKGROUND

A population sample of people with Down syndrome has been studied from infancy and has now been followed up again at age 47 years.

METHODS

Intelligence and language skills were tested and daily living skills assessed. Memory/cognitive deterioration was examined using two test instruments.

RESULTS

Scores on verbal tests of intelligence changed little. Those on a non-verbal test, on self-help skills and on both memory tests showed some decline, even when the scores of those already suffering from dementia were discounted.

CONCLUSIONS

At age 47, scores on most tests of even the majority of the cohort (i.e. those not definitely diagnosed with dementia) showed some decline. While this includes the scores of people who may subsequently develop dementia, it may also reflect the normal ageing process in this population.

Dementia in intellectual disability

PURPOSE OF REVIEW

Dementia is emerging as a significant condition in the population with intellectual disability. This review is aimed at clinicians working in the field. We revisit what is known on the subject and expand on this with results from recent research. The emphasis of this review is on the clinical research rather than laboratory or molecular research.

RECENT FINDINGS

Research has encompassed all aspects of dementia in intellectual disability, from epidemiology, assessment and diagnosis, through to management. There remains a lack of evidence concerning both pharmacological and nonpharmacological treatment of dementia in people with intellectual disability. Recent research has tended to focus on dementia in Down syndrome.

SUMMARY

More research is necessary in order to translate improvements in the understanding of the neuropathology of intellectual disability and dementia into effective treatments. There is also a need to investigate the optimum environment in which to provide holistic care for individuals affected.

Neurodevelopmental and psychiatric issues in Down's syndrome: assessment and intervention

Down's syndrome (DS) is the most frequent genetic cause of intellectual disability and patients with DS show significant psychopathology (18-23%). Moreover, individuals with DS often show a cognitive decline associated with ageing characterized by a deterioration in memory, language and cognitive functioning. According to these relevant findings, an overview is presented of state-of-the-art knowledge of the neurocognitive, neurobiological and psychopathological profile, assessment and treatment of patients with DS. The linguistic characteristics of DS develop differently along distinct developmental trajectories. Thus, for example, morphosyntax deficit, especially in production, is more evident in adolescence than in early childhood and lexicon is usually better preserved in all ages (at least in comprehension). So far, rehabilitation is the only effective approach for improving cognitive and linguistic abilities. However, ongoing preliminary reports on other approaches such as transmagnetic stimulation or drugs suggest alternative or integrative treatment for the future. Individuals with DS show typical organization of brain structures related to some cognitive abilities, such as reduced volume in frontal and prefrontal areas, which is related to poor executive and linguistic abilities. They also frequently show psychiatric disorders such as externalizing disorders as well as depression, anxiety and obsessive-compulsive disorder. Nevertheless, as for other genetic syndrome with intellectual disability, there is a significant lack of research specifically focused on treatments of psychiatric and behavioural problems in DS. This is true both for psychosocial and for pharmacological interventions.