Detecting Dementia Earlier: The development and analysis of Spatial & Episodic Memory tests for cognitive ageing and Alzheimer’s disease.

Abstract

Reliably detecting Alzheimer’s disease (AD) earlier is a global priority, to ensure that therapies can be propitiously targeted to those who most need them. Current diagnostics are not sufficiently accurate, and the best cannot be scaled to large populations. Diagnostic tools which are cost-effective, sensitive to early neurodegeneration, and easy-to-administer are crucial to progress. The hippocampal formation degenerates early on in AD, therefore tests which tap hippocampal function may prove valuable in detecting early-stage AD. The present thesis explored this idea.
Chapter 3 examined current AD tests. I meta-analysed which existing neuropsychological tests best predict early AD (i.e. conversion from MCI to AD). Results identified six neuropsychological tests of promise and suggested these may provide diagnostic performance similar to that of ‘gold-standard’ cerebrospinal fluid (CSF) markers.
Chapter 4 asked whether a recently developed spatial memory task (4MT), and a forced-choice space and sequence memory video task (SSEVT) specifically developed for this project, were sensitive to the age-related decline in cognitive ability thought to be hippocampus-dependent. As hypothesised, the SSEVT and to some extent the 4MT did, and unexpectedly the commonly used ACE-III test did not, show such sensitivity. An advantage of the SSEVT over the 4MT was that education was not significantly associated with SSEVT performance.
Chapter 5 compared the performance of MCI patients to healthy-ageing (HA) controls on the above three tasks (4MT, SSEVT and ACE III), and two self-report questionnaires (one probing spatial ability, one probing social embedding) developed for this project. Promisingly, the 4MT and SSEVT discriminated well between the MCI and HA groups, as predicted (while the ACE-III task did not). The two groups did not differ on the spatial ability questionnaire. The MCI group were less socially embedded than the HA group, offering some support for ideas that social interaction protects against dementia and cognitive decline.