Abstract
Down syndrome (DS), the most common genetic cause of intellectual disability, is associated with an ultra-high risk of developing Alzheimer's disease. However, there is individual variability in the onset of clinical dementia and in baseline cognitive abilities prior to decline, particularly in memory, executive functioning, and motor coordination. The LonDownS Consortium aims to determine risk and protective factors for the development of dementia and factors relating to cognitive abilities in people with DS. Here we describe our cognitive test battery and related informant measures along with reporting data from our baseline cognitive and informant assessments. We developed a cognitive test battery to assess general abilities, memory, executive function, and motor coordination abilities in adults with DS, with informant ratings of similar domains also collected, designed to allow for data on a broad range of participants. Participants (n=305) had a range of ages and abilities, and included adults with and without a clinical diagnosis of dementia. Results suggest the battery is suitable for the majority of adults with DS, although approximately half the adults with dementia were unable to undertake any cognitive task. Many test outcomes showed a range of scores with low floor and ceiling effects. Non-verbal age-adjusted IQ scores had lower floor effects than verbal IQ scores. Before the onset of any cognitive decline, females aged 16-35 showed better verbal abilities compared to males. We also identified clusters of cognitive test scores within our battery related to visuospatial memory, motor coordination, language abilities, and processing speed / sustained attention. Our further studies will use baseline and longitudinal assessments to explore factors influencing cognitive abilities and cognitive decline related to ageing and onset of dementia in adults with DS.
Highlights
Down syndrome (DS) is the most common genetic cause of intellectual disability (ID) and is caused by the presence of an additional chromosome 21
As anticipated, when converting Kaufman Brief Intelligence Test 2 (KBIT-2) raw scores to IQ we found a high number of adults at floor, with 70 (66.7%) adults at floor for verbal IQ and 41 (39.4%) adults at floor for non-verbal IQ
Our results suggest the majority of our tasks have high completion rates for adults who do not have a diagnosis of dementia, with test scores showing a wide range and select outcomes showing low floor and ceiling effects
Summary
Down syndrome (DS) is the most common genetic cause of intellectual disability (ID) and is caused by the presence of an additional chromosome 21. Individuals with DS have been reported to show slower motor responses compared to MA controls (Edgin et al, 2010; Frith & Frith, 1974) These general profiles of cognitive abilities are found for individuals with DS at the group level, there is a large variability both across and within individuals in cognitive profiles. There is individual variability in the onset of clinical dementia and in baseline cognitive abilities prior to decline, in memory, executive functioning, and motor coordination. Methods: We developed a cognitive test battery to assess general abilities, memory, executive function, and motor coordination abilities in adults with DS, with informant ratings of similar domains collected, designed to allow for data on a broad range of participants.
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