Do cognitive reserve levels affect brain glucose metabolism and amyloid-β depositions in subjective cognitive decline subjects?

Subjective cognitive decline (SCD) is the preclinical stage of Alzheimer's disease (AD). Abnormal brain glucose metabolism and Aβ depositions can be observed in SCD subjects. Nevertheless, there was not cognitive impaired performance in standardized neuropsychological in these subjects. Cognitive reserve (CR) could be the reason to explain this phenomenon. However, correspondence between CR and SCD was still uncleared. In this study, we attained 74 subjects underwent 18FFDG PET scans (SCD1 group) and 38 patients underwent 18FAV45 PET scans (SCD2 group) from Xuanwu Hospital, Beijing, China. First, SCD1 group was divided into SCD1H (high CR, n=33, educational years>12) and SCD1L (low CR, n=41, educational years<=12) groups. The SCD2 group was divided into SCD2H (high CR, n=17, educational years>12) and SCD2L (low CR, n=21, educational years<=12) groups. Second, we calculated standardized uptake value rate (SUVR) values of 18FFDG PET and 18F-AV45 PET images in voxel-wise level. Third, the two-sample t-test between low and high CR groups was used to investigate the effects of CR. As a result, the SUVR values of FDG-PET images in SCD1H (0.89±0.11) were significant lower than SCD1L (0.96±0.13, p=0.017). The SUVR values of AV45PET images in SCD2H (0.63±0.11) were significant lower than SCD2L (0.78±0.15, p=0.001). In addition, the frontal lobe was found as the main area of hypometabolism and reduced AB depositions. As a conclusion, there are differential glucose metabolism and Aβ deposition patterns in SCD subjects between low and high CR groups.