Discrepancy Between Cognitive Test and Brain Imaging Results in Alzheimer’s Disease Associated with Diabetes

Although a large number of studies have been performed on the association between Alzheimer's disease (AD) and type 2 diabetes mellitus (DM), the underlying pathophysiology of AD associated with DM has not been fully elucidated to date. We compared cognitive functions and brain imaging findings between AD patients with and without DM to characterize the association between cognition and imaging findings in AD patients with DM.Cognitive functions and brain imaging findings, including medial temporal lobe atrophy analyzed by magnetic resonance imaging, and hypoperfusion in the parietal, posterior cingulate, and frontal regions analyzed by single-photon emission computed tomography were compared between 126 AD patients without DM ([AD-DM]) and 51 AD patients with DM ([AD+DM]). Factors associated with cognitive-imaging associations, including education, occupation, leisure activity, comorbidity, frailty, and other demographics, were analyzed.The [AD+DM] group showed significantly more severe cognitive dysfunction than the [AD- DM] group, despite a similar degree of brain imaging abnormalities. Among the factors associated with cognitive-imaging associations, the level of leisure activity was significantly lower in the [AD+DM] group than in the [AD-DM] group, but no significant differences in other factors were observed between the 2 groups.The cognitive-imaging discrepancy observed in AD patients with DM may be associated with their low cognitive reserve, possibly caused by their low amount of leisure activities. Our findings suggest that lifestyle interventions, including physical, cognitive, and social activities, may reduce cognitive decline in AD patients with DM.