Longitudinal changes in functional disability in Alzheimer's disease patients

Background: Functional impairment is a core symptom of Alzheimer's disease (AD) often measured by loss of ability to perform activities of daily living (ADL). The objective is to describe the progressive loss of specific ADL functional capabilities expressed by AD patients' cognitive ability. Methods: Data are from ELN-AIP-901, an observational study of cognitive progression in participants aged 50-85 with AD (n = 196), mild cognitive impairment (n = 70), or cognitively normal (n = 75). Participants were evaluated using the Mini-Mental Status Exam (MMSE) and the Disability Assessment for Dementia (DAD) every six months for = 2 years. Hierarchical regression was used to estimate annual change in DAD and MMSE; first, by individuals' rate of change using linear regression, then controlling for baseline diagnosis. Results: Over a two-year period, in AD participants, a 1-point change in MMSE was associated with a 3-point change in DAD (2.79, 95% CI: 1.97-3.63); DAD items within the finance, medication, and outings subdomains were impacted earlier than other subdomains; a hierarchy of functional impairment was observed, with instrumental ADL generally impaired prior to basic ADL. Conclusions: ADL are impacted in a progressive and hierarchical manner associated with cognitive decline, but substantial variability remains among individuals, as well as in the relative order of items affected.