Quality of Life in Dementia Patients and Their Proxies: A Narrative Review of the Concept and Measurement Scales

Abstract

Dementia profoundly affects quality of life of patients as well as family and caregivers. Quality of life (QOL) refers to people’s emotional, social and physical wellbeing, and their ability to function in daily life. QOL measures attempt to evaluate directly the impact of dementia or interventions on people’s ability to function in life. Besides this global conceptualization of QOL there is a growing field of research on QOLmeasures focused on the measurement of health related quality of life (HRQL), i.e., a person’s satisfaction or happiness with domains of life insofar as they affect or are affected by the dementia. HRQL can be distinguished from QOL in that it concerns itself primarily with those factors that fall under the purview of health care providers and health care systems (>QOL/HRQL). QOL measurement provides a subjective evaluation that captures benefits and harms of interventions not detected by standard clinical outcomes. Three methods of QOL assessment are available: selfreport, proxy-report and > proxy rating by direct observation of behavior assumed to be related to QOL. Acknowledging the problem of potential bias of proxy-reports, self-report methods are preferable if possible. If not, observational methods by an uninvolved professional are an acceptable alternative. By content, QOL measurement scales also can be categorized into three groups: generic, domain-specific or disease-specific. Generic scales can be divided in health profiles and utility measurements. Health profiles classify subjects with respect to a broad spectrum of QOL domains, thus producing a descriptive profile from several health domains. Generic utility measures enable cost-utility analysis. Cost is measured in monetary units. Benefit is usually expressed in quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs). Domain-specific questionnaires rate QOL on circumscript areas, such as mobility, physical restrictions, autonomy or mastery. Dementia-specific measures probably have a higher grade of > responsiveness, i.e., a higher ability to identify changes that relate to the natural course of dementia or treatment interventions. QOLmeasurement methods in dementia are still facing important challenges. Measurement properties encompass reliability, validity and responsiveness. Responsiveness, the ability to detect relevant change over time in health status, is an essential property of outcome measures for intervention studies and still largely unclear in dementia research. Another important item is response shift, referring to the psychological adaptation of perception of QOL following a change in health status (e.g., progress of the dementia), which should also be addressed adequately. Next to the differential effects of dementia on the patients themselves, caring for people with dementia is often associated with increase in distress and decrease in mental health and wellbeing, thus affectingQOLof proxies as well. Therefore, despite the remaining scientific challenges in the field, it is highly recommendable to includeQOL assessment of patients and proxies as endpoints in all dementia and MCI intervention trials. List of Abbreviations: AAI, Activity and Affect Indicators of quality of life; AD, Alzheimer’s disease; ADR-QL, Alzheimer’s Disease health-Related Quality of Life scale; BASQID, Bath Assessment of Subjective Quality of Life in Dementia; CBS, Cornell-Brown Scale for quality of life in dementia; CEA, cost-effectiveness analysis; CUA, cost-utility analysis; DALY, disabilityadjusted life years; DCM, Dementia Care Mapping; DHP, Duke Health Profile; DQOL, Dementia Quality of Life scale; DSDAT, Discomfort Scale-Dementia of Alzheimer Type; EQ5D, European Quality of life 5 Dimensions; EQ-6D, European Quality of life 6 Dimensions; HRQL, health related quality of life; HSQ, Health Status Questionnaire; HUI, Health Utilities Index;MCI,Mild Cognitive Impairment;MID,minimal important difference; NHP, Nottingham Health Profile; PDS, Progressive Deterioration Scale; PRO, patient reported outcome; PTO, person trade-off; PWB-CIP, Psychological Well-Being in Cognitively Impaired Persons; Quality of Life in Dementia Patients and Their Proxies 213 3673 QALY, quality-adjusted life year; QOL, quality of life; QOL-AD, Quality of Life-Alzheimer’s Disease scale; QOL AS, Quality of Life Assessment Schedule; QOL-D, Quality of Life for Dementia; QUALID, Quality of Life in Late-Stage Dementia scale; QWB, Quality of WellBeing scale; RI, responsiveness index; SEM, structural equation modeling; SEIQOL, Schedule for the Evaluation of Individual Quality of Life; SF-6D, SF-36 revised into a six-dimensional health state classification: SF-36, Medical Outcomes Study 36-item Short Form Health Survey; SF-12,Medical Outcomes Study 12-Item Short Form Health Survey; SG, standard gamble; SIP, Sickness Impact Profile; TTO, time trade-off; VAS, visual analogue scale; WHOQOL 100, World Health Organization Quality of Life 100