Predictors of Family Caregiver Ratings of Patient Quality of Life in Alzheimer Disease: Cross-Sectional Results from the Canadian Alzheimer's Disease Quality of Life Study

Objectives To assess whether the core symptoms of Alzheimer disease (AD) and caregiver factors consistently predict family caregiver ratings of patient quality of life (QOL) as assessed by a variety of QOL measures in a large national sample. Design Cross-sectional. Setting Fifteen dementia and geriatric clinics across Canada. Participants Family caregivers (n = 412) of community-living patients with AD of all severities. Measurements Caregiver ratings of patient QOL using three utility indexes, the European Quality of Life-5 Dimensions, Quality of Well-Being Scale and Health Utilities Index; a global QOL visual analogue scale; a disease-specific measure, the Quality of Life-Alzheimer's Disease; and a generic health status measure, the Short Form-36. Patient cognition was assessed with the cognitive subscale of the Alzheimer's Disease Assessment Scale and Mini-Mental State Examination, function with the Disability Assessment for Dementia, and behavioral and psychological symptoms with the Neuropsychiatric Inventory and the Geriatric Depression Scale. Caregiver burden was assessed with the Zarit Burden Interview and caregiver depression with the Center for Epidemiologic Studies Depression scale. One-way analysis of variance and fully adjusted multiple linear regression were used to assess the relationship between patient dementia symptom and caregiver variables with QOL ratings. Results In multivariable analyses, caregiver ratings of patient function and depressive symptoms were the only consistent independent predictors of caregiver-rated QOL across the QOL measures. Conclusions Caregiver ratings of patient function and depression were consistent independent predictors of caregiver-rated QOL, using a spectrum of QOL measures, while measures of patient cognition and caregiver burden and depression were not. These findings support the continued use of caregiver ratings as an important source of information about patient QOL and endorse the inclusion in AD clinical trials of caregiver-rated measures of patient function, depression, and QOL.