P2‐189: PREVALENCE AND PROGNOSIS OF “PRODROMAL AD” (DUBOIS ET AL.) ASSESSED WITH MRI AND FDG‐PET IN A COMMUNITY: REANALYSIS FROM THE OSAKI‐TAJIRI PROJECT

Background: We previously examined 42 subjects with Clinical Dementia Rating (CDR) 0.5 with FDG-PET and followed them for 5 years (Int Psychogeriatr 2008). Twenty had converted to Alzheimer’s disease (AD). They had a lower baseline glucose metabolism (CMRglc) in the right cingulate, left parietal/temporal gyrus compared. Dubois et al. (Lancet Neurol 2007) proposed the criteria for "prodromal AD" which needs MRI and FDG-PET findings. Our database can provide information on the prevalence of the condition. Methods: A neuroradiologist classified the PET images blindly to the clinical findings based on the Silverman’s criteria (JAMA 2001): progressive patterns (P1, P2, P3) and non-progressive pattern s (N1, N2, N3). Subjects were considered to have prodromal AD if they showed P1 FDG-PET pattern (Parietal/Temporal +/Frontal hypometabolism) together with hippocampal atrophy as assessed with MRI. Their CDR Memory domains were all 0.5 or 1, showing episodic memory impairment, fulfilling the criteria for "prodromal AD." The prevalence and prognosis of the condition were retrospectively analyzed. Results: Seventeen subjects were diagnosed as prodromal AD, indicating 40.5% among the CDR 0.5 population and 25.0% among the total older adults aged 65 years or older. Twelve out of 17 (70.6%) converted to AD during the 5-year follow up period, which was higher than previously reported ratio (J Neurol Sci 2007) from the total CDR 0.5 population (37.0%). Conclusions: The concept and criteria for "prodromal AD" is useful to predict the converters to AD in a community. A comprehensive system including CDR, cognitive tests, MRI and PET, is recommended in community based health policy planning.