Characteristics of very late-onset schizophrenia-like psychosis classified with the biomarkers for Alzheimer’s disease: a retrospective cross-sectional study

We aimed to investigate the association between very late-onset schizophrenia-like psychosis (VLOSLP), a schizophrenia spectrum disorder with an onset of ≥60 years, and Alzheimer's disease (AD) using biomarkers. Retrospective cross-sectional study. Neuropsychology clinic of Osaka University Hospital in Japan. Thirty-three participants were classified into three groups: eight AD biomarker-negative VLOSLP (VLOSLP-AD), nine AD biomarker-positive VLOSLP (VLOSLP+AD), and sixteen amnestic mild cognitive impairment due to AD without psychosis (aMCI-P+AD) participants. Phosphorylated tau levels in the cerebrospinal fluid and F-Florbetapir positron emission tomography results were used as AD biomarkers. Several scales (e.g. the Mini-Mental State Examination (MMSE), Wechsler Memory Scale-Revised (WMS-R) Logical Memory (LM) I and II, and Neuropsychiatric Inventory (NPI)-plus) were conducted to assess clinical characteristics. Those in both VLOSLP-AD and +AD groups scored higher than those in aMCI-P+AD in WMS-R LM I. On the other hand, VLOSLP+AD participants scored in between the other two groups in the WMS-R LM II, with only VLOSLP-AD participants scoring significantly higher than aMCI-P+AD participants. There were no significant differences in sex distribution and MMSE scores among the three groups or in the subtype of psychotic symptoms between VLOSLP-AD and +AD participants. Four VLOSLP-AD and five VLOSLP+AD participants harbored partition delusions. Delusion of theft was shown in two VLOSLP-AD patients and five VLOSLP+AD patients. Some VLOSLP patients had AD pathology. Clinical characteristics were different between AD biomarker-positive and AD biomarker-negative VLOSLP, which may be helpful for detecting AD pathology in VLOSLP patients.