Evidence of executive dysfunction, disinhibition and apathy in cognitive decline and Alzheimer\'s dementia in people with Down syndrome

Author(s)

Luciana Mascarenhas Fonseca

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2018-11-30

Examining board members

Marcelo Queiroz Hoexter; Ivan Aprahamian; Sérgio Luís Blay; Monica Sanches Yassuda

• Advisor: Marcelo Queiroz Hoexter

Abstract

INTRODUCTION. Although a neuropathological correlation has been established between Down syndrome (DS) and Alzheimer\'s disease (AD), the early symptoms of dementia present atypically in the DS population. There is evidence that frontal-subcortical circuits play an important role in the initial presentation of dementia in DS, including changes in behaviour and executive dysfunction. The present study aimed to investigate factors associated with frontal lobe functioning (executive dysfunction, disinhibition and apathy) during cognitive decline and AD in adults with DS. METHODS. 92 individuals with DS aged over 30 years were evaluated and divided into three groups of diagnosis (stable cognition, prodromal dementia and AD) using the Cambridge Examination for Mental Disorders in Adults with Down Syndrome and others with Intellectual Disability (CAMDEX-DS), previously validated as part of our methodology. Participants were assessed with an executive function protocol developed for people with intellectual disabilities by researchers from University of Cambridge, and were rated for executive dysfunction, disinhibition and apathy by an informant using the Frontal Systems Behavior Scale (FrSBe). In addition, data on characteristics of frontal behaviour, memory and orientation were analysed through CAMDEX-DS in conjunction with an English sample totalling 162 participants with DS over 30 years old and divided into four groups: stable cognition under 45 years, stable cognition above 45 years, prodromal dementia and AD. RESULTS. Reports of executive dysfunction, disinhibition and apathy through FrSBe were correlated with participants\' cognitive performance: the higher the behavioural dysfunction in these areas, the worse the cognitive performance in executive tasks. Disinhibition and executive dysfunction were associated with diagnoses. The odds of having AD increased in parallel with increases in FrSBe scores (p <= 0.5). In the CAMDEX-DS analysis, amnestic and non-amnestic symptoms were found to be present before there was evidence of a cognitive decline. During the progression to dementia, those symptoms tended to worsen. Memory and orientation were poorer in the prodromal dementia group than in the stable cognition group (odds ratio 35.07, P < 0.001) as was executive function (odds ratio 7.16, P < 0.001). Disinhibition was greater in the AD group than in the prodromal dementia group (odds ratio 3.54, P = 0.04), and apathy was more pronounced in the AD group than in the stable cognition group (odds ratio 34.18; P < 0.001). CONCLUSION. Executive dysfunction, disinhibition and apathy were present in individuals with DS and stable cognition. These measures hasten the initial cognitive decline of AD and are related with cognitive performance in executive function tasks. Frontally mediated behaviour should be taken into consideration during the clinical evaluation of adults with DS. Future studies considering the intersection of neuropathology, brain connectivity, and behaviour may aggregate knowledge about the basis and nature of these associations, leading to the development of effective preventive strategies (AU)

• FAPESP's process: 13/11571-9 - Risk factors for dementia and cognitive decline in adults with Down Syndrome and the CAMDEX-DS validation
• Grantee: Luciana Mascarenhas Fonseca
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)