Reduced differentiation of personality in Alzheimer's disease–like dementia and associations between informant report of personality change and cognitive decline

BackgroundPersonality changes are documented in Alzheimer's disease (AD), but research has focused almost exclusively on how much traits change rather than how the underlying personality structure reorganizes. Recent evidence from healthy aging shows that personality traits can de-differentiate over time, suggesting a decline of coherence of traits with age. Whether such personality de-differentiation also occurs in neurodegeneration and how personality and cognitive changes relate remains unknown.ObjectiveThis study aimed to examine structural changes in personality traits in individuals with AD-like dementias, using the HEXACO personality model administered cross-sectionally to informants and to a control group of informants of healthy older adults, and explore dimensional changes in the relationship between reported changes in personality and cognition.Methods207 informants of persons with AD-like dementia and 201 informants of healthy older adults completed the Hexaco Adjective Scales, referring both to the present time and to perceived changes in personality, and a questionnaire (e-Cog) to assess cognitive changes.ResultsPrincipal component analysis revealed a simplified personality structure in persons with AD but not in healthy older adults, with Emotionality not emerging as an independent factor in persons with AD. Network analyses indicated significant links between personality trait changes and declines across cognitive domains that differed between the two groups.ConclusionsAD-like dementias are characterized by a reduced differentiation of personality structure paralleling the simplification of cognitive organization, with the strongest impact observed in the Emotionality domain. Personality changes also co-occur with perceived cognitive decline, underscoring the need to integrate personality assessment in evaluating dementia.