Proxy-rated quality of life in Alzheimer's disease: a three-year longitudinal study

Background: The study investigated the change in proxy rated quality of life (QoL) of a large cohort of home living patients with Alzheimer's disease (AD) over a period of 36 months. Methods: The sample consisted of 102 patients with mild AD and their primary caregivers from the Danish Alzheimer's Disease Intervention Study. QoL was assessed with the proxy-rated (primary caregivers) Quality of Life in Alzheimer Disease scale (QOL-AD) and the EuroQuol Visual Analogue Scale (EQ-VAS) scale. The Cornell Scale for Depression in Dementia (CSDD), Alzheimer's Disease Cooperative Study, Activities of Daily living Inventory (ADCS-ADL), Mini-Mental State Examination (MMSE) and Neuropsychiatric Inventory (NPI-Q) were also applied. Evaluations were conducted at baseline and at 12 and 36 months follow-up. Results: There was a significant decline in mean QoL assessed by both the QOL-AD and the EQ-VAS (p < 0.001). There were vast individual differences in the QoL scores on both scales at 12 and 36 months' follow-up. Mean change from baseline in QOL-AD was significantly associated with change in CSDD, ADCS-ADL and MMSE scores at 12 months and with ADCS-ADL score at 36 months. Conclusion: QoL is a subjective concept and may not be influenced by the degree of cognitive dysfunction. Future studies should investigate the factors for individual variations in order to understand the nature of change of QoL in AD and the wide variation in QoL scores over time.