Do we agree or disagree? A systematic review of the application of preference-based instruments in self and proxy reporting of quality of life in older people

Quality of life is an important person-centred outcome in health and aged care settings. Due to an increasing prevalence of cognitive decline and dementia in ageing populations, a proportion of older people receiving health and aged care services may not be able to reliably assess their own quality of life, highlighting the need for proxy assessment. This systematic review sought to investigate the level of agreement between self and proxy-report of older people's quality of life using established preference-based instruments of quality of life suitable for economic evaluation. A systematic review was conducted following PRISMA guidelines. Eight databases were searched: Web of Science, Scopus, Medline, Econlit, PsychINFO, CINAHL, Ageline and Cochrane Library. Information was extracted on the instruments, population samples (including any cognitive thresholds applied), mean scores, type of proxy, and measures of inter-rater agreement. A total of 50 studies using eight different preference-based quality of life instruments were identified. Most studies were cross-sectional (72%) with a wide variety of cognitive assessments and thresholds applied to define older participants with cognitive impairment. The most common proxies were family members, mostly spouses. The level of agreement between self and proxy-report was generally poor - irrespective of the instrument applied or type of proxy - with proxy-report generally indicating lower levels of quality of life than self-report. There was some evidence of stronger agreement on more observable quality of life domains e.g., physical health and mobility, relative to less observable domains e.g. emotional well-being. Few studies tracked self and/or proxy-report of quality of life longitudinally. More research is needed to develop evidence to inform guidance on self-report versus proxy-report of quality of life for older people receiving health and aged care services. Until then, the collection of both self and proxy reports as complementary measures is indicated. •Quality of life is an important person-centred outcome in health/social care.•Self-assessment is preferable but not always possible due to cognitive impairment.•Agreement between older people and proxies is generally poor.•There is higher agreement for more observable quality of life dimensions.•Proxies adopting older person perspective can result in greater agreement.