Episodic memory performance and associated grey matter volume in older adults with type 2 diabetes mellitus

Abstract

Type 2 Diabetes Mellitus (DM2) results in peripheral and central nervous system complications. Recent studies suggest that DM2 accelerates age-related cognitive decline and is specifically linked to Alzheimer Disease (AD). A commonly reported impairment reported in DM2 is in learning and memory, and macroscopic brain changes that could mediate memory impairments can be detected by quantifying grey matter volume with Magnetic Resonance Imaging (MRI). This thesis project predicts that older adults in DM2 have impaired learning and memory compared with older adults without DM2. Additionally, the DM2 group would have decreases in grey matter volume of the hippocampus and associated brain regions, which would mediate memory function. The study found that the DM2 group performed significantly worse on two validated neuropsychological measures of learning, recall and recognition. The difference was highly significant in the learning and memory of face-name pairs, suggesting that assessing higher-level memory functions could be a sensitive marker for subtle memory impairments. However, the two groups did not differ in grey matter volume of the hippocampus, the medial temporal lobe, or the hippocampal network. Additionally, grey matter volume was not associated with learning and memory measures. The findings suggest that memory changes in DM2 may not be mediated by brain atrophy, rather could be mediated by microscopic brain changes earlier in AD progression such as beta amyloid accumulation, hyperphosphorylated tau protein, or reduced synaptic plasticity.