The relationship between changes in quality of life outcomes and progression of Alzheimer's disease: results from the dependence in AD in England 2 longitudinal study.

Abstract

The relationship between conventional indicators of Alzheimer's disease (AD) progression and quality of life (QoL) outcomes is unclear. Dependence on others has been recommended as a unifying construct in defining AD severity. This study examined the relationship between indicators of disease severity (including dependence) and changes in QoL and utility over 18 months. A multi-centre, cohort study was conducted across 18 UK sites. One hundred and forty-five patients with possible/probable AD and their caregivers completed assessments of disease severity (Dependence Scale, Mini-mental state examination, Neuropsychiatric Inventory, Disability Assessment for Dementia), dementia-specific QoL (DEMQOL, DEMQOL-Proxy) and generic health-related utility (EQ-5D) at both time points. There was evidence of individual change in QoL over 18 months, with over 50% of patients reporting either maintenance or improvement of life quality. The EQ-5D proxy suggested a mean decline in QoL, whereas the DEMQOL-Proxy indicated overall improvement. In the subsample of people who self-reported QoL and utility, no mean change was evident. Changes in dependence did not explain changes on any QoL or utility outcome. There was a weak association between the EQ-5D proxy and changes in cognition, whereas changes on the DEMQOL-Proxy were partly explained by changes in behavioural disturbance. The natural progression of AD over 18 months does not lead to inevitable decline in QoL or utility. There are no clear or consistent direct relationships between changes in disease severity and QoL outcomes. The impact of increasing dependence and worsening disease severity is likely buffered by a combination of psychological, social and environmental factors.