Conversion to dementia in very late-onset schizophrenia-like psychosis classified with Alzheimer's disease and Lewy body disease biomarkers: A retrospective cohort study

This study aimed to examine the conversion rate to dementia and cognitive changes in individuals with very late-onset schizophrenia-like psychosis (VLOSLP) classified with Alzheimer's disease (AD) and Lewy body disease (LBD) biomarkers. Patients with VLOSLP were retrospectively enrolled in the study, and follow-up assessments were conducted at least once up to approximately 2 years. Participants were classified into AD and LBD biomarker-negative (BMs-neg), AD-biomarker-positive and LBD biomarker-negative (AD-pos/LBD-neg), and LBD biomarker-positive (LBD-pos) groups. The conversion rate during the study period and longitudinal cognitive changes between the initial and final assessments were analyzed. Nineteen participants were enrolled in the study among patients who visited the neuropsychology clinic of the Department of Psychiatry, Osaka University Hospital, for the first time between 2018 and 2023. The conversion rates to dementia were 14%, 67%, and 50% in the BMs-neg, AD-pos/LBD-neg, and LBD-pos groups, respectively, without a significant difference (p = 0.187). At the follow-up assessment, all four participants who experienced conversion in the AD-pos/LBD-neg group were diagnosed with AD dementia, while in the LBD-pos group, two of such patients were diagnosed with dementia with Lewy bodies, and one was diagnosed with idiopathic normal pressure hydrocephalus. The only participant in the BMs-neg group converted was diagnosed with an unclassified form of dementia. Mixed-design analysis of variance revealed a significant group-by-time interaction in the Clinical Dementia Rating sum of boxes (p = 0.004). Patients with VLOSLP who are positive for AD and/or LBD biomarkers may be more likely to progress to dementia within 2 years than those who are negative.