Incidence of and risk factors for hallucinations and delusions in patients with probable AD.

OBJECTIVE: To examine the incidence of and risk factors for hallucinations and delusions associated with patients clinically diagnosed with probable AD.
BACKGROUND: Estimates of the incidence of psychosis in AD range widely from 10% to 75%. The risk factors for psychosis of AD are not known, although multiple studies indicate that AD patients with psychosis demonstrate greater cognitive and functional impairment.
METHODS: The authors conducted psychiatric evaluations of 329 patients with probable AD from the University of California at San Diego Alzheimer's Disease Research Center to determine the incidence of hallucinations and delusions. They examined data from annual clinical and neuropsychological evaluations to determine whether there were specific risk factors for the development of hallucinations and delusions.
RESULTS: Using Cox survival analyses, the cumulative incidence of hallucinations and delusions was 20.1% at 1 year, 36.1% at 2, 49.5% at 3, and 51.3% at 4 years. Parkinsonian gait, bradyphrenia, exaggerated general cognitive decline, and exaggerated semantic memory decline were significant predictors. Age, education, and gender were not significant predictors.
CONCLUSIONS: The authors found a relatively high incidence of hallucinations and delusions in patients diagnosed with probable AD and suggest that specific neurologic signs, cognitive abilities, and accelerated decline may be predictive markers for their occurrence.