Cognitive Reserve proxies for individuals with intellectual disabilities: a Scoping Review

Abstract

AbstractBackgroundDementia in people with Intellectual Disability (ID) has a prevalence three times greater (Strydom et al., 2007) and with an earlier onset (Dodd et al., 2015) than in the general population. Despite the fact that virtually all adults with ID display neuropathology consistent with dementia by the age of 40, many of them never show the clinical symptoms (Strydom et al., 2009): there is no linear link between degree of brain damage and severity of the symptomatology (Arvio & Bjelogrlic‐Laakso, 2021). This discrepancy could be attributed to a difference in Cognitive Reserve (CR, Stern, 2009). However, CR has never been systematically studied specifically in relation to ID. To fill this gap, we aimed to identify potential indicators (“proxies”) of CR specifically relevant for people with ID to be included in future instruments. Indeed, activities potentially promoting and enhancing CR in people with ID may not overlap with those considered by the instruments for the general population (see CRIq, Nucci et al., 2012).MethodA Scoping Review was conducted in PubMed and Scopus. N = 1239 potentially relevant papers were identified, 104 papers were assessed for eligibility and 17 studies matched our inclusion criteria.ResultWe consider as proxies of CR all lifestyle factors and life experiences proven in past studies to be positively correlated with the cognitive performance or with the everyday functioning of adults with ID, even if not explicitly labeled as proxies of CR. Some proxies found are partly overlapping with the ones used to quantify CR in the general population: Education, Occupation, Leisure and Physical activity. Yet, others are uniquely suitable for the population with ID: Type of schooling, Parental educational level, Environmental stimulation and Living place. Those should be incorporated within the instruments developed and validated in the future to assess the CR of people with ID.ConclusionThis Review is the first step toward the development of the first instrument to measure CR in people with ID. The hope is that it will be integrated among the instruments routine used in the clinical practice and assure people with ID an early and accurate diagnosis of dementia.