Effect of Amyloid on Cognitive Performance in Parkinson's Disease and Dementia with Lewy Bodies

Background: Concomitant amyloid pathology contributes to the clinical heterogeneity of Lewy body diseases (LBDs). Objective: The objective of this study was to investigate the pattern and effect of amyloid accumulation on cognitive dysfunction in Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Methods: We retrospectively assessed 205 patients with LBD (91 with DLB and 114 with PD) who underwent ¹⁸F-florbetaben positron emission tomography and divided them into amyloid-positive and amyloid-negative groups depending on global standardized uptake value ratios (SUVRs). We investigated the effect of group on the regional and global SUVRs using general linear models (GLMs) after controlling for age, sex, cognitive status, and score on the Korean version of the Mini-Mental State Examination. Moreover, the effect of amyloid on cognitive function, depending on the type of LBD, was evaluated using GLMs with interaction analysis. Results: In all evaluated regions including the striatum, the DLB group showed a higher SUVR than the PD group. Among amyloid-positive patients, the DLB group had a higher regional SUVR than the PD group in the frontal and parietal cortices. There was a significant interaction effect between amyloid and disease groups in language and memory function. In patients with PD, global amyloid load was negatively associated with language (B = −2.03; P = 0.010) and memory functions (B = −1.96; P < 0.001). However, amyloid load was not significantly associated with cognitive performance in the DLB group. Conclusions: Although the burden of amyloid was higher in the DLB group, amyloid accumulation was negatively associated with the memory and language functions in the PD group only.