Longitudinal 18F-FDG Images in Patients With Alzheimer Disease Over More Than 9 Years From a Preclinical Stage

BACKGROUND: Brain F-FDG uptake reportedly starts to decline more than 10 years before the onset of cognitive decline in dominantly inherited Alzheimer disease (AD). We compared longitudinal F-FDG images in sporadic AD to aging data from a large sample size to expand the current knowledge of F-FDG reduction for AD progression. METHODS: Participants comprised 2 individuals (subjects A and B at ages 65 and 68 years, respectively) and 107 control subjects (67.9 [SD, 4.9] years). Subject A underwent F-FDG PET a total of 8 times over 9 years from the preclinical to early dementia stages. Subject B underwent F-FDG PET a total of 11 times over 12 years from the preclinical to mild cognitive impairment stages. Control subjects underwent F-FDG PET twice over a mean follow-up period of 7.8 years. After placing the volume of interest on the AD-related hypometabolic regions, the longitudinal F-FDG images were compared among the subjects and control subjects. RESULTS: For the control group, the rate of F-FDG reduction was 2.2% per decade (ie, aging effects). The rates of F-FDG reduction were 9.41% over 9 years and 9.07% over 12 years in subjects A and B, respectively. We estimated that F-FDG uptake started to decrease 4 and 2 years before indications of memory loss in subjects A and B, respectively. CONCLUSIONS: The present study suggests that the time between the beginning of F-FDG reduction and the onset of cognitive decline may be shorter in elderly individuals with AD compared with the recently estimated period in dominantly inherited AD.