Dementia and the intellectual disability population: insights into the early presentation and approaches to assessment

Abstract

It is widely acknowledged that individuals with intellectual disability are more susceptible to dementia than the general population however the reason for this is unclear. Theories include variation in pre-existing levels of cognitive ability, genetic components, and the presence of additional comorbidities. Individuals with Down’s Syndrome are also at increased risk due to a triplication of chromosome 21. Dementia is characterised by progressive decline however the early manifestation in this population is uncertain. As a result, a systematic review was conducted to explore the early symptoms associated with dementia in individuals with intellectual disability. 18 studies were included and analysed using narrative synthesis. The review found evidence that changes in multiple domains, including memory, executive function, attention, mobility, and behaviour were observed early in the course of dementia. The review emphasises the need for assessments to be broad in nature to encompass domains other than memory that may demonstrate early decline.
In light of this, there is a need for valid and reliable tools exploring a range of functions to be developed for the intellectual disability population. Although numerous assessment tools exist, only a small proportion were designed specifically for this population. The empirical study explored the psychometric properties of a newly developed battery aimed at assessing dementia in this population. 23 participants across different NHS settings completed the battery. The results suggest the battery demonstrates good internal consistency although the validity of the measure could not be established due to the small sample size. Floor and ceiling effects were present across several subtests. This battery appears to be a promising measure for use within the intellectual disability population however further amendments are required regarding the inclusion of certain subtests and scoring guidance. Further research should seek to verify the validity of the battery in comparison to other established measures.

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Identifiers

ORCID for Jade Dunning: orcid.org/0000-0001-7390-296X

ORCID for Warren Dunger: orcid.org/0000-0002-3213-5175

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