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Background
Dementia is one of the most common and serious disorders in later life. It causes irreversible decline in global intellectual and physical functioning, and has a significant personal, social, health and economic impact on people with dementia, their family carers, and health and social services. Although measures of cognitive, functional and behavioural outcomes are widely used to evaluate interventions for dementia, the challenge of measuring broader outcomes such as health-related quality of life (HRQoL) has only recently begun to be addressed. This presents challenges about how to assess the subjective perceptions and experiences of the person with dementia in a reliable and valid way. This report describes the development of a new measure (DEMQOL) to evaluate HRQoL in people with dementia. The new measure is designed to address limitations and/or gaps that were identified in existing dementia-specific measures.
Objectives
The purpose of this study was to develop and validate a psychometrically rigorous measure of HRQoL for people with dementia. The measure was intended to be: suitable for use in the UK; available in self- and proxy-report versions for people with dementia and their carers, respectively; and appropriate for use in mild/moderate and severe dementia. The aim was to keep the perspective of the person with dementia central in all stages of questionnaire development and evaluation.
Methods
Gold-standard psychometric techniques were used to develop DEMQOL and DEMQOL-Proxy. First, a conceptual framework was generated from a review of the literature, qualitative interviews with people with dementia and their carers, expert opinion and team discussion. Items for each component of the conceptual framework were drafted and piloted to produce questionnaires for the person with dementia (DEMQOL) and carer (DEMQOL-Proxy). Extensive two-stage field testing of both measures was then undertaken in large samples of people with dementia (n = 130) and their carers (n = 126), representing a range of severity and care arrangements. In the first field test, items with poor psychometric performance were eliminated separately for DEMQOL and DEMQOL-Proxy to produce two shorter, more scientifically robust instruments. In the second field test, the item-reduced questionnaires were evaluated along with other validating measures (n = 101 people with dementia, n = 99 carers) to assess acceptability, reliability and validity.
Results
The conceptual framework included...