Impairment of Episodic-Specific Autobiographical Memory in Individuals with Subjective Cognitive Decline and in Patients with Prodromal or Mild Alzheimer’s Disease

Abstract

Background: Autobiographical memory (AM) is a personal form of memory that becomes impaired in the early, clinical stages of Alzheimer’s disease (AD). In the “preclinical” phase of AD, neuropathological hallmarks are present (especially in a brain network underpinning AM), but performance on standardized neuropsychological tests is normal. Even so, some patients have subjective cognitive decline (SCD). Objective: The aim was to 1) investigate AM performance on two tests with different approaches in SCD, and in prodromal and mild AD, and 2) examine the association between the AM tests. Methods: We included 17 SCD patients with heightened risk of AD, 17 amnestic mild cognitive impairment (aMCI) patients, 17 patients with mild dementia due to AD, and 30 healthy controls. Patients were diagnosed according to international criteria, and all participants had MMSE scores≥24. AM was assessed using the Columbia Autobiographical Memory Interview-Short Form (CAMI-SF) and the Three Events Test. These tests measure the production of contextual details. Results: Significant group effects were found for the Three Events Test and the CAMI-SF. All patient groups produced significantly fewer contextual details than the controls on the Three Events Test. On CAMI-SF, the aMCI and mild AD groups were able to answer fewer questions or gave significantly less detailed answers than the other groups. The SCD patients performed below the controls on CAMI-SF, but the difference was not significant. Conclusion: AM may be impaired in very early AD, even in the phases where standardized episodic memory tests show no decline.

Subjective Complaints are Similar in Subjective Cognitive Decline and Early-Stage Alzheimer’s Disease when Assessed in a Memory Clinic Setting

“…Background data are presented in Table 1 along with results from the cognitive and neuropsychiatric screening tests (data previously presented in Bruus, Waldemar, Vogel). 15 Group comparisons showed no significant differences in gender. There were significant group effects in age, F (3, 77) = 6.3, P < .01, scores on the MMSE, χ 2 (3) = 31.5, P < .001, scores on the ACE, χ 2 (3) = 41.3, P < .001, and scores on the GDS-15, χ 2 (3) = 13.4, P < .01.…”

“…The inclusion process and the neuropsychological battery was previously described. 15 Three memory tests were applied – of which one was the Rey Auditory Verbal Learning Task (RAVLT). All patients were examined for one or more AD biomarkers (CSF Aβ 42 , CSF p-tau, PiB-PET standardized uptake value ratio, FDG-PET glucose metabolism pattern, and/or medial temporal atrophy).…”

Past and future episodic detail retrieval is reduced among clinically normal older adults at higher genetic risk for late-onset Alzheimer’s disease

“…Given that APOE4 accounts for as much as half of all late-onset cases of Alzheimer's disease [11,12], these findings suggest that altered autobiographical thinking may be part of the protracted trajectory of cognitive decline leading to clinical symptoms [13], and may be evident before many standard cognitive test scores are affected. This conclusion is supported by additional work on subjective cognitive decline [14] and the relationship between preclinical amyloid and autobiographical knowledge [15].…”

Past and future episodic detail retrieval is reduced among clinically normal older adults at higher genetic risk for late-onset Alzheimer’s disease.

“…Given that APOE4 accounts for as much as half of all late-onset cases of Alzheimer’s disease (Corder et al, 1993; Saunders et al, 1993), these findings suggest that altered autobiographical thinking may be part of the protracted trajectory of cognitive decline leading to clinical symptoms (Caselli et al, 2020), and may be evident before many standard cognitive test scores are affected. This conclusion is supported by additional work on subjective cognitive decline (Bruus et al, 2021) and the relationship between preclinical amyloid and autobiographical knowledge (Buckley et al, 2014).…”

“…However, these findings should be investigated further as this was an exploratory analysis based on smaller sample sizes. It would also be interesting to compare the impact of APOE4 on remembering and imagining relative to other Alzheimer’s disease risk factors in clinically normal older adults, such as subjective cognitive decline (Bruus et al, 2021; Pike et al, 2021; van Harten et al, 2018). Notably, although our inclusion criteria included being independent in functional activities of daily living, we did not formally assess subjective cognitive decline, which is a limitation of the present study.…”