Abstract
Down syndrome (DS) is the most common genetic cause of intellectual disability (ID). Abilities relating to executive function, memory and language are particularly affected in DS, although there is a large variability across individuals. People with DS also show an increased risk of developing dementia. While assessment batteries have been developed for adults with DS to assess cognitive abilities, these batteries may not be suitable for those with more severe IDs, dementia, or visual / hearing difficulties. Here we report the development of an informant rated questionnaire, the Cognitive Scale for Down Syndrome (CS-DS), which focuses on everyday abilities relating to executive function, memory and language, and is suitable for assessing these abilities in all adults with DS regardless of cognitive ability. Complete questionnaires were collected about 128 individuals with DS. After final question selection we found high internal consistency scores across the total questionnaire and within the executive function, memory and language domains. CS-DS scores showed a wide range, with minimal floor and ceiling effects. We found high interrater (n = 55) and test retest (n = 36) intraclass correlations. CS-DS scores were significantly lower in those aged 41+ with significant cognitive decline compared to those without decline. Across all adults without cognitive decline, CS-DS scores correlated significantly to measures of general abilities. Exploratory factor analysis suggested five factors within the scale, relating to memory, self-regulation / inhibition, self-direction / initiation, communication, and focussing attention. The CS-DS therefore shows good interrater and test retest reliability, and appears to be a valid and suitable informant rating tool for assessing everyday cognitive abilities in a wide range of individuals with DS. Such a questionnaire may be a useful outcome measure for intervention studies to assess improvements to cognition, in addition to detecting dementia-related cognitive decline. The CS-DS may also be a useful tool for other populations with ID.
Highlights
Down syndrome (DS) is the most common genetic cause of intellectual disability (ID), occurring due to the presence of an extra chromosome 21
Concepts for potential questions were identified based on their relevance to one of three main domains, with the final composite consisting of a total of 66 questions pertaining to executive function (36 questions), memory (18 questions), and language (12 questions)
Analyses were performed for questionnaires on a total of 128 individuals
Summary
Down syndrome (DS) is the most common genetic cause of intellectual disability (ID), occurring due to the presence of an extra chromosome 21. The impairments in executive function and memory in DS have been associated with altered brain development of the prefrontal cortex and hippocampus respectively, with both of these regions having smaller volumes in people with DS in neuroimaging studies [9,10,11]. This is possibly related to later developing networks being affected more in DS than other brain structures [12]. A recent functional magnetic resonance imaging (fMRI) study suggested atypical functional organisation for language processing in DS [13]
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