Dementia quality of life instrument--construct and concurrent validity in patients with mild to moderate dementia

Background and purpose: To translate the Dementia quality of life instrument (DQoL) into German and assess its construct and concurrent validity in community‐dwelling people with mild to moderate dementia. Methods: Dementia quality of life instrument data of two pooled samples (n = 287) were analysed regarding ceiling and floor effects, internal consistency, factor reliability and correlations with corresponding scales on quality of life (Quality of Life in Alzheimer‘s Disease and SF‐12), cognition (Mini‐Mental State Examination, Alzheimer’s Disease Assessment Scale – cognitive), depression (Cornell Scale for Depression in Dementia) and activities of daily living (Interview of Deterioration in Daily Living Activities in Dementia). Results: We found no floor effects (<2%), minor ceiling effects (1–11%), moderate to good internal consistency (Cronbach’s α: 0.6–0.8) and factor reliability (0.6–0.8), moderate correlations with self‐rated scales of quality of life (Spearman coefficient: 0.3–0.6) and no or minor correlations with scores for cognition, depression or activities of daily living (r < 0.3). The original five‐factor model could not be confirmed. Conclusion: The DQoL can be used in dementia research for assessing positive and negative affect, feelings of belonging and self‐esteem. The findings suggest further research to improve the structure of the scales aesthetics, feelings of belonging and self‐esteem.