Validity and Reliability of the German Quality of Life–Alzheimer’s Disease (QoL-AD) Self-Report Scale

Abstract

Background: The Quality of Life–Alzheimer’s Disease (QoL-AD) scale is a widely used measure of quality of life (QoL) in dementia. Although the instrument has been validated in several languages, the psychometric properties of the German self-report version have not yet been analyzed. Objective: This study examines the internal consistency, test-retest reliability, and construct validity of the German QoL-AD self-report scale. Methods: The sample included 30 patients suffering from mild to moderate Alzheimer’s disease or vascular dementia (19 females; mean age 77.3 years; mean Mini-Mental State Examination (MMSE) score 19.7 points). To determine test-retest reliability, the QoL-AD self-report scale was re-administered four to seven days apart. For construct validity analysis, the Dementia Quality of Life instrument (DQoL), Geriatric Depression Scale (GDS), MMSE, and an adapted short form of the Neuropsychiatric Inventory (NPI) were used. Results: The German QoL-AD self-report scale shows an internal consistency of α= 0.79 and a test-retest reliability of r = 0.75 (p < 0.01). Regarding construct validity, there was a significant positive correlation between the total scores of the QoL-AD and DQoL (r = 0.47, p < 0.05). The analysis revealed no significant correlations with the GDS or the adapted NPI. No association could be observed between the QoL-AD and the MMSE (r = 0.01), confirming divergent validity. Conclusion: The results indicate that the German QoL-AD self-report scale is a suitable instrument for assessing QoL in patients suffering from mild to moderate dementia, thus supporting its use in clinical practice and research.