Cognitive deterioration in Alzheimer's disease: behavioral and health factors.

Alzheimer's disease is characterized by progressive cognitive decline. However, little is known about the "typical" rate of decline, the degree of individual heterogeneity evident in decline, or the types of factors that influence such decline. This study investigated these questions in a sample of 106 patients with Alzheimer's disease, assessed at 1-5 points in time, spanning up to three years. At each time point, the Mini-Mental State Exam, a measure of global cognitive function, was administered to all patients. Measures of behavioral disturbance (including the presence/absence of hallucinations, depression, incontinence, wandering, and agitation), health status (including presence/absence of neurological, cardiovascular, and other diseases), and descriptive information (such as gender, age at time of onset, and duration of deficits) were obtained at entry into the study. A two-stage random effects regression model was fit to the data and then used to assess the effect of these behavioral, health, and descriptive measures on the rate of decline. Results indicate that the rate of cognitive decline in Alzheimer's disease is quite variable. Patients with various health and behavioral problems declined at a rate between 1.4 and 5 times faster than patients without such problems. Alcohol abuse, additional neurological disease, and agitation were significantly related to rate of decline. Overall number of problems was not. The association of these problems with accelerated decline may have prognostic and treatment implications.