Epidemiology of and risk factors for psychosis of Alzheimer's disease: a review of 55 studies published from 1990 to 2003.

OBJECTIVE: The authors reviewed studies published between 1990 and 2003 that reported the prevalence, incidence, and persistence of, as well as the risk factors associated with, psychosis of Alzheimer's disease.
METHOD: PubMed and PsycINFO databases were searched by using the terms "psychosis and Alzheimer disease" and "psychosis and dementia." Empirical investigations presenting quantitative data on the epidemiology of and/or risk factors for psychotic symptoms in Alzheimer's disease were included in the review. A total of 55 studies, including a total of 9,749 subjects, met the inclusion criteria.
RESULTS: Psychosis was reported in 41% of patients with Alzheimer's disease, including delusions in 36% and hallucinations in 18%. The incidence of psychosis increased progressively over the first 3 years of observation, after which the incidence seemed to plateau. Psychotic symptoms tended to last for several months but became less prominent after 1 year. African American or black ethnicity and more severe cognitive impairment were associated with a higher rate of psychosis. Psychosis was also associated with more rapid cognitive decline. Some studies found a significant association between psychosis and age, age at onset of Alzheimer's disease, and illness duration. Gender, education, and family history of dementia or psychiatric illness showed weak or inconsistent relationships with psychosis.
CONCLUSIONS: Psychotic symptoms are common and persistent in patients with Alzheimer's disease. Improved methods have advanced the understanding of psychosis in Alzheimer's disease, although continued research, particularly longitudinal studies, may unveil biological and clinical associations that will inform treatments for these problematic psychological disturbances.