Predictors of patient self-ratings of quality of life in Alzheimer disease: cross-sectional results from the Canadian Alzheimer's Disease Quality of Life Study

Abstract

Objectives: To assess whether the core symptoms of Alzheimer disease (AD) consistently predict patient self-rated quality of life (QOL) as assessed by a variety of QOL measures in a large national sample of AD patients.

Design: Cross-sectional.

Setting: Fifteen dementia and geriatric clinics across Canada.

Participants: Community-living patients with AD (n = 370) with Mini-Mental State Exam (MMSE) scores greater than 10.

Measurements: Patients rated their QOL by using two utility indexes, the European QOL-5 Dimensions and the Quality of Well-Being Scale, a global QOL Visual Analog Scale, and the disease-specific QOL-AD instrument. Cognition was assessed with the AD Assessment Scale-Cognitive subscale and MMSE, function with the Disability Assessment for Dementia, and behavioral and psychological symptoms with the Neuropsychiatric Inventory and the Geriatric Depression Scale (GDS). One-way analysis of variance and fully adjusted multiple linear regression were used to assess the relationship between core dementia symptoms and QOL ratings.

Results: The QOL measures had only small-to-moderate correlations with each other. For all QOL measures, patient ratings were significantly lower among patients with more depressive symptoms. In multivariable analyses, the GDS score was the only significant independent predictor of patient self-ratings for all four QOL measures.

Conclusions: Self-rated symptoms of depression were a consistent independent predictor of patient-rated QOL across diverse QOL measures, while performance-based measures of cognition and informant-based functional status were not. These findings confirm the importance of identifying and treating depression in patients with AD and endorse the use of measures of self-rated depressive symptoms and QOL as outcomes in AD clinical trials.

Figure. Estimated regression coefficients and their 95% confidence intervals for the GDS sub-scale variables related to the depressed mood, apathy, anxiety, cognitive impairment, and other items of the GDS

GDS = Geriatric Depression Scale; EQ-5D = European Quality of Life-5 Dimensions; QWB = Quality of Well-Being Index; VAS = Global Quality of Life Visual Analog Scale; QOL-AD = Quality of Life-Alzheimer’s Disease. For each quality of life outcome variable, the regression coefficients were calculated from four fully adjusted regression models. Each regression analysis was adjusted for patient age, sex, marital status, first language, Charlson score, Alzheimer’s Disease Assessment Scale-Cognitive Subscale, Disability Assessment for Dementia, Neuropsychiatric Inventory and study center, as well as for the other GDS sub-scale variables. The QOL-AD scores were normalized to a 0–1 scale. The degrees of freedom for calculating the 95% confidence intervals ranged from 288 to 291.