Alzheimer’s disease (AD) is one of the most well-known and frequent neurodegenerative disease affecting the older population. At advanced stages of AD, the majority of the patients may suffer from a lack of awareness of his/her impairments, a symptom that is called anosognosia. Anosognosia is often measured using the discrepancy between the patient’s perception of his/her memory ability and the informant’s perception of the same. Recent longitudinal studies have shown that anosognosia seems to develop as the disease progresses. Thus, it could be hypothesized that the disorder is the cause of accumulating pathology in the brain causing a disruption of the person’s ability to accurately estimate his/her memory functions. In this study, we sought to investigate the relationship between memory awareness and two of hallmark pathologies of AD, amyloid and tau. In line with our hypothesis, we found that as these two pathologies increased, the patient’s awareness decreased (mainly driven by the fact that the informant’s complaints increased while the patient’s complaints remained relatively low. These results demonstrate that anosognosia is caused by the progressive accumulation of certain lesions characteristic of AD and thus, it may be important to assess both the patient and the informant complaints of memory.
Introduction: Impaired self-awareness of memory function is a common symptom in Alzheimer’s disease (AD), however it’s pathological correlates remain unclear. Here we investigated the impact of AD biomarkers (amyloid and tau) on memory self-awareness.
Methods: 218 clinically normal (CDR=0) and 123 clinically impaired (CDR 0.5) participants from the ADNI cohort, with ECog questionnaires, amyloid-positron emission tomography (PET) and tau-PET scans for two regions (entorhinal and inferior temporal cortices), were included. We computed a participant-informant discrepancy index as a measure of awareness.
Results: At higher levels of pathology (i.e., both amyloid and tau), clinically impaired individuals demonstrated significantly lower awareness than clinically normal participants. Our results also showed a significant effect of tauopathy on individual complaint, in both regions; but not of amyloidosis.
Discussion: Impaired self-awareness of memory function is associated with higher levels of amyloid and tau in clinically impaired individuals. Discordant subjective and objective measures may be important for clinical consideration.