Functional competency and cognitive ability in mild Alzheimer's Disease: relationship between ADL assessed by a relative/carer-rated scale and neuropsychological performance

Background: Alzheimer's disease (AD) is characterized by multiple cognitive deficits and affects functional competency to perform daily activities (ADL). As this may contribute to the patient's overall disability, it is important to identify factors that compromise competency. Objective: The relationship between different cognitive domains and functional activities in AD was studied. Methods: The functional competency of 73 Japanese AD patients, most with mild dementia, was assessed using a 27-item relative/carer-rating scale covering 7 ADL: managing finances, using transportation, taking precautions, self-care, housekeeping, communication and taking medicine. Cognitive assessment used 16 neuropsychological tests from the Japanese version of the WAIS-R and COGNISTAT, covering 9 cognitive domains: orientation, attention, episodic memory, semantic memory, language, visuoperceptual and construction abilities, computational ability, abstract thinking, and psychomotor speed. Results: Multiple regression analysis by the stepwise method indicated that functional competency could, for the most part, be predicted from test scores for orientation, abstract thinking and psychomotor speed. Discussion: The results of this study suggest that impairment of these three cognitive domains plays an important role in the functional deterioration of AD.