The association between age and cognition and behaviours in adults with Down syndrome, without dementia: an investigation of frontally mediated cognitive functions, adaptive behaviours and behavioural and emotional problems

Abstract

Background: More people with Down syndrome (DS) are now living into adulthood when compared with the previous two generations. There is a paucity of information, both cognitive and behavioural, on this adult ageing process, particularly for those adults who do not develop dementia. Consequently, this thesis aimed to examine the associations between age and: (A) frontally mediated cognitive functions (sustained attention, inhibition and working memory), (B) adaptive behaviours, (C) behavioural and emotional problems in adults with DS, without dementia. Method: Fifty-three adults with DS (aged 16-56 years), without a diagnosis of dementia, and their caregivers were involved in the longitudinal and/or cross sectional studies presented in this thesis. Adults with DS completed the Peabody Picture Vocabulary Test-4 and a battery of sustained attention, working memory and inhibition experimental cognitive tasks. Caregivers completed the Adaptive Behaviour Dementia Questionnaire, the Developmental Behavioural Checklist-Adult, the Adaptive Behaviour Assessment System- II Adult, and demographic information. Results: Domain specific, rather than pervasive, age associations were seen for the cognitive tasks and the adaptive behaviour measure. Specifically for adaptive behaviour, stability for practical abilities was reported, whereas age associated declines in conceptual and social skills was observed. For cognition, age related declines in working memory and inhibition are reported in the context of stable sustained attentional abilities. A differential impact of task sensory modality (i.e. auditory verses visual) was also described for the inhibition measure. In particular, the auditory inhibition task was associated with age related declines, however the visual version showed no such age association. No associations between age and behavioural and emotional problems were observed for any variable. Conclusions: This thesis provided support for the contention that age associations for adaptive behaviours and frontally medicated cognitive functions were domain specific rather than pervasive in adults with DS, without dementia. A number of hypotheses to explain these domain specific age associated patterns are discussed throughout the thesis. Of particular note, the idea that areas with pre-existing weaknesses may be more susceptible to age related change than areas without such weaknesses were explored for all cognitive and behavioural domains. Support was not found for domain specific age associations or susceptibility for areas of pre-existing weakness in terms of behavioural and emotional problems in adults with DS, without dementia. This finding was not considered surprising given that cognition and adaptive behaviours are conceptually more closely related than behavioural and emotional problems, particularly with respect to ageing. Implications: The findings from this thesis highlight the importance of research analysing individual cognitive and behavioural domains, rather than relying solely on global measures of cognition and behaviours. Additionally, the benefits of expressing behavioural scores in terms of the specific factors that make up the score (e.g. range and severity) were highlighted. Translated to clinical practice, this thesis provides guidance as to strengths and weaknesses, and how these are associated with age in adults with DS, without dementia. Such information may allow practitioners to better target cognitive and behavioural supports and interventions. Such supports are necessary in promoting and maintaining a sense of autonomy, skill mastery, satisfaction, self-esteem, community participation, and engagement for adults with DS.