Early Markers for Dementia in the Intellectual Disability Population: A Systematic Literature Review.

Most included studies recruited people with Down syndrome, so the findings say little about dementia in intellectual disability without Down syndrome, and the authors state the results cannot be applied to the wider intellectual disability population. The studies used 66 different measures, including tests developed for the general population that are not validated for intellectual disability, so differences between studies may reflect the tools used rather than real differences in symptoms. Only three of the eighteen studies followed people over time, and many compared groups at different stages without a prodromal comparison, so the order in which symptoms appear cannot be determined. Many studies relied on informant reports for behaviour and daily skills, which are subject to recall and interpretation bias. People with severe or profound intellectual disability and those lacking capacity to consent were largely excluded, so the findings may not apply to your most disabled patients. Studies varied in how they defined prodromal dementia, and some had small numbers in each subgroup, limiting how much weight to give individual findings.

The research was a Doctorate in Clinical Psychology thesis supported by the University of Southampton. The authors declare no conflicts of interest.

Do not read this as evidence that a change in behaviour, gait or daily skills confirms early dementia. The review found no agreement on which symptom appears first, most studies were cross-sectional rather than tracking change over time, and the findings mainly reflect Down syndrome rather than intellectual disability generally.