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 alpha: 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.