The relationship between acquired impairments of executive function and behaviour change in adults with Down syndrome

Abstract

The latter stages of dementia in individuals with Down syndrome are well documented; however, earlier cognitive and behavioural changes have only recently been described. Holland et al. suggested such early signs of dementia in this population are behavioural and are similar to those seen in frontotemporal dementia, but there is, as yet, no evidence to determine whether such behavioural changes are associated with a declines in specific cognitive functions, including those associated with the frontal lobes. A longitudinal design of three time points across 16 months was used across 30 adults with Down syndrome aged 30 years and over. Measures of cognition (Neuropsychological Assessment of Dementia in Individuals with Intellectual Disabilities), receptive language (British Picture Vocabulary Scales), adaptive behaviour (Vineland Adaptive Behavior Scales), behavioural excesses and behavioural deficits (Assessment for Adults with Developmental Disabilities) and measures of executive functioning were completed at each time point. Using a data-driven method, cognitive deterioration was determined using the Reliable Change Index on performance on the Neuropsychological Assessment of Dementia in Individuals with Intellectual Disabilities across the duration of the study. Performance on the remaining measures were then compared between those with (n = 10) and those without (n = 20) cognitive deterioration. Only individuals with cognitive deterioration showed decreases on measures of executive function and significant changes in behaviour across the duration of the study, which was not solely due to declines in memory. There were no changes between the groups on levels of adaptive behaviour. Even in the early stages of cognitive deterioration, specific behavioural changes can be identified that are not present in those without cognitive deterioration. The differing effects of cognitive deterioration on behavioural excesses and deficits are discussed in relation to potentially differing underlying neuropathological causes.