Identification of diabetes-related dementia: Longitudinal perfusion SPECT and amyloid PET studies.

AIMS: We attempted to identify a dementia subgroup with characteristics associated with diabetes mellitus (DM)-related metabolic abnormalities, referred to as diabetes-related dementia, using longitudinal single photon emission computed tomography (SPECT) and Pittsburgh compound-B (PiB) positron emission tomography (PET). METHODS: We classified 175 patients with clinically diagnosed Alzheimer disease (AD) and DM into 4 subgroups based on brain imaging in a 2013 study. Among them, we investigated follow-up SPECT studies in 29 patients of an AD group showing decreased regional cerebral blood flow (rCBF) of the parietotemporal lobe on initial SPECT and 18 patients of a diabetes-related dementia group showing neither decreased rCBF of the parietotemporal lobe nor cerebrovascular disease, which is strongly associated with DM-related factors. Eleven of them underwent PiB PET. RESULTS: Follow-up SPECT showed more profound rCBF reduction in the parietotemporal lobe and other areas of the AD group, whereas follow-up SPECT showed an rCBF reduction in small areas of the frontotemporal and limbic lobes of the diabetes-related dementia group. Six of 9 patients with diabetes-related dementia were negative or equivocal for PiB binding. CONCLUSION: A subset of a dementia subgroup with characteristics predominantly associated with DM-related factors may underlie a pathophysiology different from AD, although these patients were clinically diagnosed as having AD. The identification of diabetes-related dementia may be necessary for considering an appropriate therapy and prevention in clinical practice.