Abstract
BackgroundAccurate assessment of health-related quality of life as an endpoint in intervention studies is a major challenge in dementia research. The DEMQOL (29 items) and the proxy version (32 items), which is partly based on the DEMQOL, are internationally used instruments. To date, there is no information on the structural validity, item distribution, or internal consistency for the German language version of these questionnaires.MethodsThis psychometric study is based on a secondary data analysis of a sample of 201 outpatients with a mild form of Alzheimer’s disease (AD) and their informal caregivers. The informal caregivers who were interviewed were involved in the care of the person with AD several times per week. The analysis for the evaluation of the structural validity was performed using Mokken scale analysis. The internal consistency was calculated using the ρ of the Molenaar Sijtsma statistic and Cronbach’s α.ResultsFor both versions, four subscales were identified: [A] “positive emotions”, [B] “negative emotions”, [C] “physical and cognitive functioning”, and [D] “daily activities and social relationships”. For both instruments, the internal consistency of all subscales was considered “good” (ρ = 0.71–0.88, α = 0.72–0.87).ConclusionsThe results are a first indication of good construct validity of the instruments used for the German setting. We recommend further investigations of the test-retest reliability and the inter-rater reliability of the proxy instrument.
Highlights
Accurate assessment of health-related quality of life as an endpoint in intervention studies is a major challenge in dementia research
The results of the Mokken scale analysis (MSA) for the German versions of the Dementia Quality of Life (DEMQOL) and DEMQOL-Proxy are largely comparable to findings from previous studies on the Health-related quality of life (HRQoL) of persons living with dementia [4, 15], especially to the conceptual framework of Smith and colleagues [14] as well as to their explorative factor analysis of the pretest during the development of the instrument
In accordance with the HRQoL definition from Hays and Reeve [7] provided in the background, the subscales we found in our study cover the aspects of “how well a person functions in his/her life” and his or her “perceived well-being in physical, mental, and social domains of health”
Summary
Accurate assessment of health-related quality of life as an endpoint in intervention studies is a major challenge in dementia research. Approximately 46.8 million people worldwide are living with dementia [1]. Health-related quality of life (HRQoL) reflects an important desire for persons living with dementia and is used as a general endpoint in many interventional studies. HRQoL is increasingly used for assessments of anti-dementia drugs and by the European Medicines. HRQoL in persons living with dementia is considered by regulatory authorities and administrative agencies who must judge this parameter based on a resident’s degree of self-sufficiency. HRQoL is used in economic evaluations of persons in all stages of dementia [4,5,6]
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