Abstract
BackgroundMeasurement of health-related quality of life (HRQoL) in dementia is difficult. At some point people with dementia become unable to meaningfully assess their own HRQoL. At such a point in time researchers need to rely on other types of information such as observation or assessments from informal caregivers (proxies). However, caregiver assessments may be biased by several mechanisms. The current study explores whether caregivers project part of their own HRQoL in their assessments of patient HRQoL.MethodsThe participants in the current study were 175 pairs, consisting of community-dwelling persons with dementia and their caregivers. The EQ-5D, the EQ-VAS and the QoL-AD were administered to collect HRQoL measurements from patients and caregivers at baseline, 6 months and 12 months. Two linear mixed models were used to investigate factors that bias proxy ratings, one with the EQ-VAS as dependent variable, and one with the EQ-5D utility as dependent variable. The independent variables were caregiver age, caregiver sex and caregiver QoL-AD items.ResultsThe linear mixed model with EQ-VAS as dependent variable indicated that 3 caregiver characteristics, namely caregiver age, money (caregiver’s financial situation) and valuation of life as a whole were significant predictors of the patient-by-proxy VAS scores. The linear mixed model with utility value as the dependent variable showed that caregiver age and valuation of the ability to do things for fun were significant predictors of the patient-by-proxy EQ-5D utility values.ConclusionsThe current study was a first step in identifying factors that bias patient-by-proxy HRQoL assessments. It was discovered that caregivers project part of their own HRQoL onto patients when assessing patient HRQoL. This implies that patient-by-proxy HRQoL values should be interpreted with caution and not be used as a direct substitute for patient self-assessment, even when patients are no longer able meaningfully assess themselves.
Highlights
Measurement of health-related quality of life (HRQoL) in dementia is difficult
Dementia is posing a great threat for the future of current health care expenditures as future scenarios claim that dementia prevalence may have doubled or tripled by 2050 [2,3]
This mechanism of caregiver ‘projection’ has been investigated in stroke [31] and other contexts such as end-of-life decisions [32,33]. In the latter context it is acknowledged that caregivers are imperfect decision makers and projection of caregivers’ preferences guide their decisions. If such a mechanism is present in patient-by-proxy HRQoL ratings this is a type of bias of which clinicians and policy makers should be aware
Summary
Respondents The participants in the current study were dyads, consisting of community-dwelling persons with dementia and their informal caregivers, drawn from the AD-Euro RCT (a cost-effectiveness study on regular post-diagnosis care in dementia by memory clinics versus by general practitioners) [34,35]. The relationship of patient-by-proxy and caregiver self-assessed HRQoL values was investigated by looking at Pearson product–moment correlations coefficients (r) between their EQ-VAS scores. Patient-by-proxy EQ-VAS was entered as a dependent variable, while for predictor variables caregiver age, sex, and caregiver self-assessed QoL-AD items were entered. These variables were used in the model at T = 0, T = 6 and T = 12. The QoL-AD items were included to investigate which caregiver characteristics could bias patient-by-proxy assessments. The dependent variable was the patient-by-proxy EQ-5D utility value, while caregiver age, sex and the caregiver self-assessed QoL-AD items were independent variables
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