[Psychotic symptoms and Alzheimer's disease]

Abstract

Background: Psychotic symptoms appear during the course of Alzheimer's disease, but their frequency and intensity vary according to different studies and their nature remains unsettled.

Objectives: To study the frequency and intensity of psychotic symptoms in two transversal series of patients with Alzheimer's disease and analyze its relationship with the duration of the disease and severity of cognitive impairment.

Patients and methods: This study has been carried out in patients suffering from probable Alzheimer's disease (NINDS-ADRDA criteria). The stage of the disease was determined according to FAST, and the intensity of cognitive impairment in Mini Mental State Examination was classified as mild, moderate or severe. Frequency and intensity of psychotic symptoms (delusions, hallucinations and misidentifications) were determined by means of semistructured interviews (BEHAVE-AD 78 patients and CUSPAD 69 patients). The results obtained in these three groups of patients were compared through ANOVA variance analysis and mean contrast. Variance and covariance analysis were done to determine the relationship between psychotic symptoms and other variables (degree of cognitive impairment, length of evolution and stage of the disease). For this purpose, the patients with Alzheimer's disease but without psychotic symptoms were considered as control and compared to patients with psychotic symptoms.

Results: Nearly half the patients had psychotic symptoms. Delusions appeared earlier and were more frequent than hallucinations and misinterpretations. The more severe was the cognitive impairment, the more frequent and intense were psychotic symptoms, but the difference was significant only in cases with severe cognitive impairment. Hallucinations appeared mainly in patients with advanced dementia and were related firstly with the intensity of functional and cognitive impairment and secondly with the duration of the disease.

Conclusions: Mild psychotic symptoms, especially delusions, appear early during the course of Alzheimer's disease. The frequency and intensity of these symptoms increase in parallel with the functional and cognitive impairments caused by the disease. Hallucinations, which appear mainly when the dementia is severe, can be considered as an evolutive marker of the process. Psychotic symptoms differ from those occurring in other disorders, either neurologic or psychiatric in nature.