Autism spectrum disorder in older adults with intellectual disability: a scoping review

Introduction: Ireland has an ageing population of persons with intellectual disability (ID), autism spectrum disorder (ASD) and both (ID/ASD). Despite this, little is known about the prevalence of ASD and its effect on functional outcomes, psychiatric comorbidity or diagnostic issues in an older population with ID. This article reviews the literature on older adults with ID/ASD and identifies opportunities for future research in this population. Method: The authors searched the Medline, Pubmed, Embase, CINAHL and PsychInfo databases using the search terms using key words: (older adults) AND (ID OR mental retardation OR learning disability) AND (autism OR ASD). After excluding articles for relevance, a scoping review was carried out on the results retrieved. Results: Of the 1227 articles retrieved from the literature on ID and autism/ASD in older adults, 85 articles were relevant to an adult population with ID/ASD. The data were collated and are presented covering domains of diagnosis, prevalence, psychiatric comorbidities and functional outcomes. Conclusions: Despite increased prevalence in childhood ASD in the last 20 years, there is a lack of research regarding adults, especially older adults, with ASD, up to half of whom will have some level of ID. The existing literature suggests that older adults with ID/ASD may have reduced functional independence, increased psychiatric comorbidity and psychotropic prescribing and more behavioural presentations than the older population generally or those with ID only. There is a need for longitudinal data to be collected on this ageing population so that care and management needs can be met in the future.