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.