Prevalence and prognosis of prodromal Alzheimer's disease as assessed by magnetic resonance imaging and ¹⁸F-fluorodeoxyglucose-positron emission tomography in a community: Reanalysis from the Osaki-Tajiri Project

Background: Dubois etal. proposed the criteria for prodromal Alzheimer's disease (AD) to detect dementia in its very early stage. Because detection requires magnetic resonance imaging and ¹⁸F-fluorodeoxyglucose-positron emission tomography (PET), the prevalence and prognosis have not been fully investigated. Methods: Our database included 346 healthy participants (Clinical Dementia Rating (CDR) 0), 119 with questionable dementia (CDR 0.5), and 32 dementia participants (CDR 1+) and was applied to investigate the prevalence of prodromal AD. Forty-four CDR 0.5 participants (37%) were randomly selected to undergo ¹⁸F-fluorodeoxyglucose-PET. The same percentage was applied to select 128 CDR 0 and 12 CDR 1 + participants (total: n = 184) to calculate the prevalence. A neuroradiologist classified the PET images in a blinded manner based on the criteria of Silverman etal. Participants were considered to have prodromal AD if they exhibited 'parietal/temporal +/- frontal hypometabolism' (PET) with hippocampal atrophy (magnetic resonance imaging). Results: Eighteen CDR 0.5 participants (40.9%) met the criteria for prodromal AD, which was a prevalence rate of 9.8% among older adults aged ≥65years. Thirteen prodromal AD participants (72%) converted to AD during the 5-year follow-up period. Discussion: The concept and criteria for prodromal AD are useful for predicting which subjects in a community will convert to AD.