Hallucinations, delusions, and cognitive decline in Alzheimer's disease

Objectives-To examine the occurrence of hallucinations and delusions in Alz heimer's disease over a 4 year period and their association with rate of co gnitive decline. Methods-A cohort of 410 persons with clinically diagnosed Alzheimer's disea se underwent annual clinical evaluations over a 4 year period. Participatio n in follow up exceeded 90% in survivors. Evaluations included structured i nformant interview, from which the presence or absence of hallucinations an d delusions was ascertained, and detailed testing of cognitive function. Th e primary cognitive outcome measure was a composite cognitive score based o n 17 individual performance tests. The mini mental state examination (MMSE) and summary measures of memory, visuoconstruction, repetition, and naming were used in secondary analyses. Results-At baseline, hallucinations (present in 41%) and delusions (present in 55%) were common and associated with lower cognitive function. In analy ses that controlled for baseline level of cognitive function, demographic v ariables, parkinsonism, and use of antipsychotic medications, hallucination s, but not delusions, were associated with more rapid cognitive decline on each cognitive measure. In the primary model, there was a 47% increase in t he average annual rate of decline on a composite cognitive measure in those with baseline hallucinations compared with those without them. This effect was mainly due to a subgroup with both auditory and visual hallucinations. Conclusion-These findings suggest that the presence of hallucinations is se lectively associated with more rapid cognitive decline in Alzheimer's disea se.