Is quality of life in dementia patients validly estimable? A current review about measuring instruments and methodological problems

Objective The measurement of quality of life (QoL) in dementia is a methodological challenge because of the patients' cognitive impairment and anosognosia. This review gives an overview of the possibilities and methodological problems of QoL measurement in dementia patients. Methods With literature searches conducted in PubMed and Web of Sciene 12 dementia-specific QoL-measures were identified. Results Most authors agreed that patients with mild to moderate dementia themselves can validly and reliably estimate their QoL. But with increasing severity of the disease, patient ratings must mostly be replaced by proxy ratings. The latter are especially essential in longitudinal studies, but are not a satisfying substitute for the patients' perspective. Thus, the influcence of depression and care-related burden on the proxies' QoL-ratings should be controlled. Conclusions QoL-instruments, applicable to all stages of dementia should be preferred, because longitudinal QoL-measures are more meaningful than cross sectional analyses. The patients' perspective should be taken into consideration as long as possible, since proxies assess the QoL of dementia patients differently from the persons affected.