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

BACKGROUND: Adults with intellectual disability, especially those with Down syndrome, are at increased risk of dementia. Whilst memory decline is often considered the earliest symptom, emerging research indicates decline in language, executive function, and non-cognitive domains may also occur early, potentially before memory changes. METHOD: A systematic review using narrative synthesis was conducted to evaluate recent literature on early symptoms of dementia and the trajectory of decline in people with intellectual disabilities and Down syndrome. RESULTS: Eighteen peer-reviewed studies met the inclusion criteria. Early decline was observed across multiple domains, with memory and executive function frequently identified as sensitive to early decline. Attention, mobility, and behaviour were also commonly reported. CONCLUSION: The findings suggest that early dementia symptoms extend beyond memory decline, highlighting the need to broaden current assessment guidelines. Further research is required to address methodological limitations and improve early detection in this population.