LOW COGNITIVE AWARENESS, BUT NOT COMPLAINT, IS A GOOD MARKER OF PRECLINICAL ALZHEIMER'S DISEASE

Abstract

Subjective cognitive decline (SCD) is considered an early aspecific clinical marker for Alzheimer's disease (AD). In this study, we wanted to search for a specific pattern of SCD in asymptomatic individuals at risk for AD. Cognitively normal older adults (n=318) reporting SCD and their informants were enrolled in the INSIGHT-PreAD cohort. Subjects performed 6 questionnaires assessing different aspects of SCD. We examined the relationship between these SCD measures and AD neuroimaging markers (amyloid burden assessed by 18F-florbetapir (18F-AV-45 [Amyvid™, Avid Radiopharmaceuticals]) PET, hippocampal atrophy by structural magnetic resonance imaging and brain hypometabolism by FDG-PET). We introduced an index of cognitive awareness resorting to the subject-informant discrepancy in a questionnaire of SCD, and compared the participants with high versus low awareness of their cognitive functioning. None of the SCD questionnaires was correlated with AD neuroimaging markers (all r<.206). Comparing subjects with a low (n=19) and high (n=86) level of awareness, there was no significant difference in terms of demography, neuropsychiatric symptoms, autonomy, quality of life, cognition and hippocampal volume. The mean amyloid standardized uptake value ratio was significantly higher for the “low awareness” group compared to the “high awareness” group (p=.011). In addition, the proportion of amyloid positive subjects in the “low awareness” group was twice as large as in the “high awareness” group (47% vs 24%, p=.045). Furthermore, the “low awareness” group showed glucose hypometabolism, particularly in all the brain regions affected by AD (posterior cingulate cortex, inferior parietal lobule, precuneus and inferior temporal gyrus).