Background: We identified the need to develop a scientifically rigorous measure of health-related quality of life (HRQL) in dementia that would be appropriate for use at all stages of dementia severity and would be available in both self- and proxy-report versions.
Method: We used standard psychometric methods to eliminate items with poor psychometric properties (item-reduction field test) and to assess the acceptability, reliability and validity of the item-reduced instruments (psychometric evaluation field test). We developed and validated two versions of DEMQOL: a 28-item interviewer-administered questionnaire that is self-reported by the person with dementia (DEMQOL) and a 31-item interviewer-administered questionnaire that is proxy-reported by a caregiver (DEMQOL-Proxy).
Results: DEMQOL shows high reliability (internal consistency and test-retest) and moderate validity in people with mild/moderate dementia. DEMQOL-Proxy shows good acceptability and internal consistency and moderate evidence of validity in people with mild/moderate and severe dementia. Test-retest reliability and performance in people with severe dementia need further testing.
Conclusions: DEMQOL and DEMQOL-Proxy show psychometric properties that are comparable with the best available dementia-specific measures of HRQL. We recommend that DEMQOL and DEMQOL-Proxy are used together. Reliability and validity need to be confirmed in independent samples and responsiveness needs to be evaluated.