Abstract
BackgroundEstablishing the cognitive phenotype of psychotic symptoms in Alzheimer's disease (AD) could localise discrete pathology and target symptomatic treatment. This study aimed to establish whether psychotic symptoms would be associated with poorer performance on neuropsychological tests known to correlate with striatal dopaminergic function and to investigate whether these differences would be attributed to the paranoid (persecutory delusions) or misidentification (misidentification phenomena +/− hallucinations) subtype.MethodsSeventy patients with probable AD (34 psychotic and 36 nonpsychotic) were recruited to the study. Analysis of covariance was used to compare motor speed and the rapid visual processing test of sustained visual attention, after adjusting for potential confounding factors. Multivariate analyses were used to compare performance across other cognitive domains. Significant findings were explored by separating patients on the basis of subtype.ResultsRapid visual processing performance accuracy was reduced in patients with psychotic symptoms (F 1,58 = 5.94, p = 0.02) and differed significantly across subtypes (F 2,51 = 3.94, p = 0.03), largely because of poorer performance in the misidentification compared with nonpsychotic group. Multivariate analyses (corrected for multiple comparisons) showed poorer performance on the incomplete letters task in psychotic patients (F 1,63 = 8.77, p = 0.004) and across subtypes (F 2,55 = 10.90, p < 0.001), similarly attributed to the misidentification subtype.ConclusionsThese findings provide further support of the involvement of dopaminergic networks in the psychosis endophenotype in AD and, in addition, implicate the ventral (temporo‐occipital) pathway in the misidentification subtype. Future studies should investigate the early trajectory of neuropathological change in vivo across psychosis subtypes.© 2015 The Authors. International Journal of Geriatric Psychiatry published by John Wiley & Sons, Ltd.
Highlights
Psychotic symptoms are highly prevalent in people with Alzheimer’s disease (AD) (Ropacki and Jeste, 2005), manifest early in the disease course and are associated with an accelerated cognitive and functional decline (Koppel et al, 2014b)
The current study aimed to investigate the neuropsychological correlates of psychotic symptoms in psychotropic naive AD patients and to test the following hypotheses: (1) Performance on tests of motor speed and sustained visual attention previously shown to correlate with striatal dopaminergic function would differ between psychotic and nonpsychotic AD patients
International Journal of Geriatric Psychiatry published by John Wiley & Sons, Ltd
Summary
Psychotic symptoms (delusions and hallucinations) are highly prevalent in people with Alzheimer’s disease (AD) (Ropacki and Jeste, 2005), manifest early in the disease course and are associated with an accelerated cognitive and functional decline (Koppel et al, 2014b). Given the modest efficacy and adverse effect profile associated with antipsychotic use in AD (Schneider et al, 2006), there is a compelling clinical need to elucidate the pathophysiology of psychotic symptoms and identify novel therapeutic targets (Geda et al, 2013). Establishing the cognitive phenotype of psychotic symptoms in Alzheimer’s disease (AD) could localise discrete pathology and target symptomatic treatment. This study aimed to establish whether psychotic symptoms would be associated with poorer performance on neuropsychological tests known to correlate with striatal dopaminergic function and to investigate whether these differences would be attributed to the paranoid (persecutory delusions) or misidentification (misidentification phenomena +/À hallucinations) subtype
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