The Memory Binding Test: a new tool to assess emerging episodic memory decline in asymptomatic at‐risk individuals to Alzheimer’s disease

Abstract

AbstractBackgroundEpisodic memory (EM) deficits are a hallmark of Alzheimer’s disease (AD). The Free and Cued Selective Reminding Test (FCSRT) is the most specific official diagnostic tool detecting AD‐linked EM alterations in advanced preclinical stages (Grober et al., 2021). However, new tools that anticipate diagnosis to the at‐risk phase are needed, to reach more meaningful therapies. Based on existing research, we aim to investigate the Memory Binding Test (MBT) promising capacity to detect the appearance of subtle AD‐linked EM alterations and anticipate AD‐diagnosis to an at‐risk phase (Bushcke ey al., 2017; Mowrey et al., 2018).MethodsFCSRT and MBT scores were collected yearly during 5 years from the INSIGHT‐preAD cohort. We selected 3 groups controlled for age, education level, gender, beta‐amyloid burden (AB+), and neurodegeneration status based on 15 individuals who converted to prodromal‐AD during follow‐up, as follows: converters/AB+; non‐converters/AB+; controls/AB‐. Evaluation of both list‐learning tests is mainly based on free recall (FR) and total (cued) recall (TR) scores. The FCSRT uses 1‐list of words to remember while the MBT uses 2‐lists, introducing a binding component sensitive to subtle EM alterations. Data was analysed using mixed effect models including age, gender, and education as covariates.ResultsWhen compared with the FCSRT, the MBT anticipated the detection of AD‐linked EM alterations in the converters/AB+ versus the other groups. In the MBT decline started up to 5 years prior to diagnosis, in delayed FR (mainly associated to executive dysfunction), followed by decline in 4 binding‐associated scores 1 year later (linked to storage deficits associated with the amnesic hippocampal syndrome characteristic of AD). Therefore, at an at‐risk phase, MBT outperformed FCSRT, both in the year of diagnosis and in the number of scores confirming AD‐linked EM deficits.ConclusionWe show the MBT capacity to detect the initial subtle EM alterations and to anticipate diagnosis to the at‐risk phase, while participants remain cognitively normal. We argue that the MBT (at‐risk phase detection) and the FCSRT (preclinical phase classification) could be complementary rather than concurrent tools, fostering meaningful innovative treatments to prolong quality of life in AD, a disease that remains without a cure.