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Item distribution, internal consistency, and structural validity of the German version of the DEMQOL and DEMQOL-proxy

Contact Information


Christian G. G. Schwab

Dementia; Internal consistency; Quality of life; Structural validity.


Accurate 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. Methods This 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. Results For 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). Conclusions The 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.


Schwab, C. G. G., Dichter, M. N., & Berwig, M. (2018). Item distribution, internal consistency, and structural validity of the German version of the DEMQOL and DEMQOL-proxy. BMC geriatrics, 18(1), 247.





Conent Area

Christian G G Schwab

EWB-Related Construct

(2) life satisfaction; (3) positive affect; (4) quality of life;

Study Design

Species or Study Population

(1) cross-sectional

Sex (%Female)

Persons with dementia: 43.8%
Informal caregivers: 71.1%

Age (Mean, SD)

Persons with dementia: 73.74, 7.92
Informal caregivers: 64.82, 13.17

Younger Controls?


Longitudinal Data?


Sample Size




Ethnicity (%white)

not stated (Germany)

Inclusion Criteria

The first inclusion criterion required participants to be elderly outpatients with an established ICD-10 diagnosis of AD with mild severity, as defined by a Mini-Mental State Examination (MMSE) score of 21 or above.
The need for a designated informal caregiver who was involved in the care of the person living with AD several times a week was the second inclusion criterion for the study.

Exclusion Criteria

Exclusion criteria were comprised of acute psychiatric or physical disorders, ongoing formal psychotherapy or cognitive training, regular visits to day care facilities, an impending hospital or nursing home admission, a poor command of the German language, alcohol or substance dependence, and participation in another interventional trial.

EWB Measures

Dementia Quality of Life

Non-EWB Behavioral

Beck Depression Inventory (BDI)
Bayer Activities of Daily Living Scale (B-ADL)
Geriatric Depression Scale (GDS)
Neuropsychiatric Inventory (NPI)
Zarit Burden Interview (ZBI-22)

Physiological Measures


Brain IMaging Modality

Brain IMaging Paradigm


Brain Region/Circuit


Biological Measures


Other Neural Measures

Data Availability?


Data Avalability Details

All of the data necessary for a meta-analysis of the internal consistency and structural validity of the DEMQOL and DEMQOL-Proxy items are contained within the manuscript and its supplementary file. Further data are available upon request.

Diagnostic Measures

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