562. <i>IN VIVO</i> ASSESSMENTS OF TAU PATHOLOGIES IN PATIENTS WITH LATE-ONSET PSYCHOSIS: A PET STUDY

Abstract Background Late-onset psychosis (LOP) has distinct clinical features compared to younger-onset psychosis. While previous postmortem and epidemiological studies have suggested a link between the neural substrates of LOP and neurodegenerative processes, particularly tauopathies, research examining tau accumulation in the living brain of patients with LOP remains limited. Aims &amp; Objectives This study aimed to investigate the putative neuropathology of LOP by combining amyloid PET and tau PET with Florzolotau (18F) (18F-florzolotau), which can detect various tauopathies in vivo. Method Thirty-seven patients with LOP (mean age = 69.9 years) and 47 controls underwent PET with 11C-PiB and 18F-florzolotau to evaluate amyloid beta and tau accumulation. Multivariate analysis of covariance (MANCOVA) was performed to examine the effects of diagnosis on standardized uptake value ratios (SUVRs) of 18F-florzolotau for four gray matter regions (frontal, temporal, parietal, and occipital cortices), controlling for age and sex. Correlations between these SUVRs and total scores of Mini-Mental State Examination (MMSE) and Frontal Assessment Battery (FAB) were investigated. Results Patients showed a significantly higher proportion of amyloid positivity (13 patients versus one control). MANCOVA demonstrated significant effects of diagnosis on 18F-florzolotau SUVRs (p = 0.004), and post-hoc analyses showed a higher SUVR in the parietal cortex of the patients. The diagnostic effects on SUVRs remained significant when MANCOVA was restricted exclusively to amyloid-negative participants (p = 0.002). There were no significant correlations between SUVR values in these regions and total MMSE or FAB scores. Discussion &amp; Conclusions This in vivo clinical PET study suggests a potential association between the neuropathology of LOP and diverse tau pathologies. These findings contribute to a better understanding of the pathogenesis of LOP, and may facilitate the development of molecular-targeted therapeutic interventions.