Neuropsychiatric Symptoms in Alzheimer's Disease Are the Main Determinants of Functional Impairment in Advanced Everyday Activities

Background: Neuropsychiatric symptoms and cognitive impairment are independent contributors of functional impairment in activities of daily living (ADL) in Alzheimer's disease (AD) patients. ADL could be divided according to its complexity in three subdomains: basic (BADL), instrumental (IADL), and advanced (a-ADL). Objective: Studying the cognitive and neuropsychiatric determinants of BADL, IADL, and a-ADL in normal cognitive elders and AD patients. Methods: 144 subjects were graduated using the clinical dementia rating (CDR) in CDR = 0, n= 52 (control group) and 92 AD patients CDR = 0.5, n= 34 and CDR = 1&2, n= 58. They were assessed with measures of cognitive performance and neuropsychiatric symptoms that were included in regression models to measure the best predictors for each ADL subdomain at every CDR status. Results: AD patients were significantly older, and had significantly more severe functional impairment, neuropsychiatric symptoms, and cognitive decline than controls. The best predictors of functional impairment in controls and CDR = 0.5 AD patients were neuropsychiatric symptoms; in the CDR 0.5 patients, apathy severity was the most important determinant of IADL and a-ADL impairment. While in the CDR 1&2 AD patients, cognitive impairment was the principal determinant of functional impairment, being memory the best determinant of IADL and a-ADL impairment, while global cognition was of BADL impairment. Conclusions: The contribution of cognitive impairment and neuropsychiatric symptoms varied according to the subdomain of ADL, and the CDR. In very mild AD and controls the neuropsychiatric symptoms are the best predictors of more complex ADL impairment, while cognitive impairment is more important at mild to moderate states of AD.