Spatial covariance structure of tau‐PET changes more than Aβ‐PET across disease stages. (31st December 2021)

• Record Type: Journal Article
• Authors: Chen, Gengsheng
• Is Part Of: Alzheimer's & dementia. Volume 17(2021)Supplement 1
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-31
• Subjects: Alzheimer's disease -- Periodicals; Alzheimer Disease -- Periodicals; Dementia -- Periodicals; Démence; Maladie d'Alzheimer; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 616.83
• DOI: 10.1002/alz.052428
• Languages: English
• ISSNs: 1552-5260

Abstract

Abstract: Background: Alzheimer disease (AD) has a long preclinical phase with pathophysiological changes such as β‐amyloid (Aβ) accumulation in early stages followed by tau deposition. Graph theory may provide additional insights into the disease processes underlying patterns of Aβ and tau deposition (Pereira et al., 2018; Hoenig, 2018). This project uses graph theory to study the spatial covariance structure of Aβ‐PET and tau‐PET changes across disease stages. Method: This study includes 254 cognitively normal participants (Clinical Dementia Rating™ (CDR™) =0) and 41 impaired participants (CDR>0) from the Washington University Knight Alzheimer Disease Research Center (ADRC, Funding: P50AG005681; P01AG003991; P01AG026276), who underwent MRI, Aβ‐PET 18F‐AV45, and tau‐PET (18F‐AV1451). Regions of interest were defined using the Freesurfer Desikin atlas. Regional Aβ and tau standardized uptake value ratios (SUVRs) were adjusted by gender and age, and used to generate Pearson correlation matrix. Aβ and tau spatial covariance structure can be built as a collection of nodes representing the mean SUVR values from different brain regions, connected by edges representing correlated deposition quantity. BRAPH toolbox (Mijalkov, 2017) were used to calculate Binary Undirected Density (BUD) graph measures. To test for significant differences between these two groups, BRAPH performs non‐parametric permutation tests. Global graph theory measures (global and local efficiency, and modularity) are used to assess the spatial covariance structure of Aβ‐PET and tau‐PET changes. Result: No significant difference between the CDR=0 and CDR>0 groups was observed for the global measures generated from the Aβ‐PET data (Table 1 and Figure 1A‐C). However, there were significant differences between the two groups for the global measures generated from the tau‐PET data (Table 1 and Figure 1D‐F). The global and local efficiency were lower in the CDR>0 group (p=0.003 and p=0.018, respectively) indicating a higher global and local path length in the covariance structure. Moreover, the modularity was lower (p=0.005) for CDR>0 group, indicating lower fragmentation between regions in this group. Conclusion: Changes in spatial correlation associated with conversion to clinical impairment are happening in the tau pattern. These spatial covariance structure changes need further evaluation to assess their utility as a biomarker of disease progression in the preclinical phase of AD.