Developing a Quality-of-Life Measure for Carers of People with Dementia for Use in Economic Evaluations: Results from the COCOON Project

BACKGROUND AND OBJECTIVE: Providing informal care to a person with dementia can substantially affect carers' quality of life. Existing generic preference-weighted measures (e.g. EQ-5D-5L) may not fully capture the caring experience, while carer-specific measures (e.g. CarerQol), although preference weighted, cannot be used to derive quality-adjusted life-years for cost-utility analysis. The COCOON project aimed to develop a new preference-weighted quality-of-life measure for carers of people living with dementia that is suitable for cost-utility analysis. METHODS: Development of the descriptive system was informed by: (1) a literature review; (2) qualitative interviews with carers of people with dementia to assess face validity of candidate items; (3) an online survey of carers to evaluate psychometric performance (including missing data, distributions, known-group validity, convergent validity, exploratory factor analysis and item response theory analysis); and (4) consultation with an advisory group. RESULTS: An initial pool of 60 candidate items was reduced to 44 items for qualitative testing. Following interviews, the item set was refined to 35 items. Based on psychometric analyses and final advisory group consultation, the final descriptive system comprised seven items: emotional health, physical health, loss and grief, loss of freedom, loneliness, support and financial burden. Each item is measured using a five-point frequency scale from 'never' to 'always'. CONCLUSIONS: The COCOON measure is grounded in the lived experiences of carers of people living with dementia, capturing the multidimensional facets of dementia caregiving and offers a conceptually robust and policy-relevant measure for assessing carers' quality of life in economic evaluations.