Psychometric properties of inhibitory control measures among youth with Down syndrome.

BACKGROUND: Inhibitory control measures have been commonly used when assessing individuals with Down syndrome. However, minimal attention has been devoted to evaluating the appropriateness of specific assessments for use in this population, potentially leading to erroneous conclusions. This study aimed to examine the psychometric properties of measures of inhibitory control among youth with Down syndrome. We sought to examine the feasibility, presence of floor or practice effects, test-retest reliability, convergent validity and correlations with broader developmental domains of a set of inhibitory control tasks. METHODS: A sample of 97 youth with Down syndrome aged 6 to 17 years old participated in verbal and visuospatial tasks of inhibitory control including the Cat/dog Stroop, Neuropsychological Assessment Second Edition (NEPSY-II) Statue, National Institutes of Health (NIH) Toolbox Cognition Battery (TCB) Flanker, Leiter-3 Attention Sustained, and the Test of Attentional Performance for Children (KiTAP) Go/No-go and Distractibility subtests. Youth also completed standardised assessments of cognition and language, and caregivers completed rating scales. Psychometric properties on the tasks of inhibitory control were evaluated against a priori criteria. RESULTS: Apart from demonstrating negligible practice effects, adequate psychometric properties were not observed for any inhibitory control measure within the current sample's age range. One task with low working memory demands (NEPSY-II Statue) generally had better psychometric properties than the other tasks assessed. Subgroups of participants with an IQ greater than 30 and age more than 8 years were shown to be more likely to be able to complete the inhibition tasks. CONCLUSIONS: Findings suggest better feasibility for analogue tasks rather than computerised assessments of inhibitory control. Given the weak psychometrics of several common measures, future studies are required to evaluate other inhibitory control measures, specifically those with reduced working memory demands for youth with Down syndrome. Recommendations for use of the inhibitory control tasks among youth with Down syndrome are provided.

Acquisition of cognitive and communication milestones in infants with Down syndrome.

BACKGROUND: Understanding the timing of developmental milestones in typical and clinical populations facilitates intervention planning and the early detection of risk for co-occurring conditions. Normative timing of developmental milestone achievement has been established for typically developing children. However, there is little information regarding the timing of cognitive and communication skill acquisition in young children with Down syndrome (DS). The objectives of this study are to (1) provide foundational information regarding the timing of cognitive and communication skill acquisition in infants with DS and (2) facilitate the early identification of infants with risk for co-occurring conditions. METHOD: Seventy-four infants with DS (age range: 4-18 months) completed the Bayley Scales of Infant Development-III (Bayley 2006). Individual items from the cognitive and communication scales were selected for analysis. Parents provided information regarding their infant's developmental and family history. RESULTS: The percentage of infants who attained each skill was calculated within 2-month age bands. For infants who did not show skill acquisition within each age band, the rates of prematurity, heart defects, corrective heart surgery and significant illness were calculated as well. CONCLUSIONS: This study provides foundational information that can contribute to the formulation of a developmental schedule for cognitive and language milestone acquisition in infants with DS.

Confirmatory factor analysis of the BRIEF2 in a sample of youth with Down syndrome.

BACKGROUND: The factor structure of the Behavior Rating Inventory of Executive Function, second edition (BRIEF2) has been widely examined in both typically developing children and specific clinical samples. Despite the frequent use of the BRIEF2 for measuring executive functioning in individuals with Down syndrome, no study has investigated the factorial validity or dimensionality of the BRIEF2 in this population. This study aimed to address this notable gap in the literature. METHODS: Parents of 407 children and youth with Down syndrome aged 6-18 years completed the BRIEF2 as part of different studies led by six sites. Three competing models proposed by previous studies were analysed using Confirmatory Factor Analysis: the theoretical structure of the BRIEF2 where the scales were constrained to load on three factors labelled as Cognitive, Behavioral, and Emotional Regulation, a two-factor correlated model with the merged Behavioral and Emotional regulation, and a single-factor model. RESULTS: The three-factor model provided a better fit than the one- and two-factor models, yet a large correlation was observed between Behavioural and Emotional regulation factors. The results provide meaningful explanatory value for the theoretical structure of the BRIEF2. However, the Behavioral and Emotional regulation factors might be less differentiated and the two-factor structure of the BRIEF2 may also make theoretical and empirical sense. CONCLUSIONS: Although more studies are needed to further examine the factor structure of the BRIEF2 in youth with Down syndrome, this investigation provides preliminary support for the interpretation of the three executive function index scores provided by the BRIEF2: Cognitive, Behavioral, and Emotional Regulation.

Early developmental profiles among infants with Down syndrome.

BACKGROUND: Down syndrome (DS) generally predisposes children to a pattern of relative developmental strengths and challenges, but within-syndrome heterogeneity is also commonly observed across many dimensions. The present research examines whether heterogeneity in developmental presentation can be detected during infancy in DS and whether factors associated with differing profiles can be identified. METHODS: Infants with DS (n = 75; age range: 3.9-17.6 months) were administered the Bayley Scales of Infant Development III (Bayley-III). A primary caregiver provided information regarding developmental history and family demographics. Latent profile analysis was conducted to identify whether early profiles were present across the five Bayley-III domains. RESULTS: Three developmental profiles were observable within the sample: a 'Mild Delay' Profile, an 'Moderate Delay' Profile and a 'Pronounced Delay' Profile. In addition, chronological age, having received heart surgery and having received occupational therapy were associated with probability of profile membership. CONCLUSIONS: Findings from this study contribute to the growing knowledgebase regarding heterogenous presentations associated with DS and can inform early intervention planning.

Latent profiles of autism symptoms in children and adolescents with Down syndrome.

BACKGROUND: Down syndrome (DS) is associated with elevated rates of autism spectrum disorder (ASD) and autism symptomatology. To better characterise heterogeneity in ASD symptomatology in DS, profiles of caregiver-reported ASD symptoms were modelled for children and adolescents with DS. METHODS: Participants (n = 125) were recruited through several multi-site research studies on cognition and language in DS. Using the Social Responsiveness Scale-2 (SRS-2; Constantino and Gruber 2012), two latent profile analyses (LPA) were performed, one on the broad composite scores of social communication and interaction and restricted interests and repetitive behaviour, and a second on the four social dimensions of social communication, social motivation, social awareness, and social cognition. RESULTS: A three-profile model was the best fit for both analyses, with each analysis yielding a low ASD symptom profile, an elevated or mixed ASD symptom profile and a high ASD symptom profile. Associations were observed between profile probability scores and IQ, the number of co-occurring biomedical conditions reported, sex, and SRS-2 form. CONCLUSIONS: Characterising heterogeneity in ASD symptom profiles can inform more personalised supports in this population, and implications for potential therapeutic approaches for individuals with DS are discussed.

Infant precursors of executive function in Down syndrome.

BACKGROUND: Although early features of infant cognition are predictive of executive function (EF) in typically developing (TD) children, there is little information regarding the developmental origins of EF in neurogenetic conditions, such as Down syndrome (DS). METHODS: The current study compared the performance of infants with and without DS on three dimensions that are hypothesised EF precursors: visual engagement, attention shifting and action planning. Additionally, the relationship between these EF precursors at Time 1 and EF performance at Time 2 (6 months later) was examined in the DS group. Participants were 36 infants with DS, M chronological age = 12.65 months, SD = 2.11; M developmental age = 8.84 months, SD = 2.22, and 36 TD infants, M chronological age = 8.62, SD = 3.06; M developmental age = 8.64 months, SD = 3.40. RESULTS: Infants with DS visually engaged with objects for longer durations and demonstrated challenges with action planning compared with TD infants at Time 1. Attention shifting at Time 1 significantly predicted EF performance at Time 2 in the DS group. CONCLUSIONS: This study provides evidence that an early atypical presentation of EF precursors is detectable during infancy in DS and is predictive of subsequent EF performance. These findings contribute to the identification of areas of early cognitive risk in DS and can inform future interventions in this population.

Evaluating working memory outcome measures for children with Down syndrome.

BACKGROUND: There is a critical need for the psychometric evaluation of outcome measures to be used in clinical trials targeting cognition in Down syndrome (DS). This study examines a specific cognitive skill that is of particular importance in DS, working memory, and the psychometric properties of a set of standardised measurements to assess working memory in individuals with DS. METHODS: Ninety children and adolescents ages 6 to 18 years old with DS were assessed on a selection of verbal and visuospatial working memory subtests of standardised clinical assessments at two time points to examine feasibility, distributional qualities, test-retest reliability and convergent validity against a priori criteria. Caregivers also completed an adaptive behaviour questionnaire to address working memory subtests' associations with broader developmental functioning. RESULTS: The Stanford Binet-5 Verbal Working Memory, Differential Ability Scales-2 Recognition of Pictures, Stanford Binet-5 Nonverbal Working Memory and Wechsler Intelligence Scale for Children-5 Picture Span measures met the most psychometric criteria overall across the full age and IQ range of the study. Although Differential Ability Scales-2 Recall of Sequential Order and Differential Ability Scales-2 Recall of Digits Backward met the fewest a priori criteria, follow-up analyses suggested greater feasibility in specific age and IQ ranges. CONCLUSIONS: Several working memory measures appear to be psychometrically sound and appropriate for use in clinical trials for children with DS, especially when focusing on raw scores. However, floor effects on standard scores and feasibility of some measures were problematic. Guidelines for use of the working memory subtests with this population are provided.

Feasibility of a syndrome-informed micro-intervention for infants with Down syndrome.

BACKGROUND: Infants with Down syndrome (DS) are at risk for a range of phenotypic outcomes, including delays in the onset of reaching behaviour, a critical skill that facilitates early learning. This parallel-group feasibility and pilot study presents findings from a parent-mediated micro-intervention that aimed to support the development of reaching behaviour in a sample of infants with DS. METHODS: Participants were 73 infants with DS and their caregivers. Infants who qualified for the home-based intervention (based on manual skill performance on Bayley Scales of Infant and Toddler Development, Third Edition items) were randomly assigned individually or by geographical region to a treatment or an alternative treatment condition that involved toy-based interactions with caregivers. Infants in the treatment condition experienced facilitated reaching during the toy-based interactions through the use of Velcro-affixed mittens and toys. RESULTS: Forty-two infants met criteria to participate in the intervention, and 37 participated in both baseline and post-treatment visits. At post-treatment, infants in the treatment condition demonstrated shorter latencies to make contact with objects and showed higher frequencies of reach attempts and swats at objects than infants in the alternative treatment group. These findings were more pronounced when examining a chronological age-restricted subgroup of infants 5 to 10 months. CONCLUSIONS: Findings suggest that a syndrome-informed approach to targeted intervention may be a promising application of phenotyping science in DS and other neurogenetic conditions associated with intellectual disability.

Goal-directed action planning in infants with Down syndrome.

BACKGROUND: Down syndrome (DS) is a neurogenetic disorder associated with risk for executive dysfunction, or difficulties with the cognitive processes required for planning volitional, goal-directed behaviour. This study examines the developmental origins of difficulties with goal-directed action planning in infants with DS to inform our understanding of the cognitive phenotype associated with DS and its implications for intervention. METHOD: First, the study compared the performance of infants with DS (n = 44, mean chronological age = 7.5 months, SD = 2.3) and typically developing infants (n = 31, mean chronological age = 7.5 months, SD = 2.9) on plan production and planning efficiency during an early planning task. Next, potential sources of variability in planning behaviour (motor performance and sensory processing) within the DS sample were examined. All infants completed an early planning laboratory task and the Bayley Scales of Infant Development-III Cognitive Scale. The motor and sensory skills of infants with DS were assessed by the motor scales of the Bayley Scales of Infant Development-III and the Infant Sensory Profile-2. DS-related biomedical history information was provided by caregivers for the infants with DS. RESULTS: Between-group differences in planning were observed on the dimensions of strategy production and completion, such that infants with DS were less efficient in their strategy execution than typically developing infants. In the DS group, motor skills and sensory processing were associated with planning efficiency on all components of the early planning task. CONCLUSIONS: Less efficient action planning in infants with DS may disrupt the shaping of goal-directed behaviour, and the identification of early risk factors associated with planning efficiency has important implications for early intervention.