A review of quality of life in Alzheimer's disease. Part 1: Issues in assessing disease impact.

There are numerous methods available for assessing patients with Alzheimer's disease (AD) or other forms of dementia. Quality-of-life (QOL) assessment is unique among these methods, because the QOL concept itself includes a subjective component that is fundamental to its measurement. It could be argued that measuring quality of life is just as important as measuring disease severity, disease progression, symptom response, cognition, behavioural disturbance and activities of daily living when assessing the impact of disease and intervention in dementia. The subjective nature of quality of life provides healthcare professionals with the opportunity of incorporating the value systems of patients and their carers into their assessments. A systematic review was carried out to include the published data (and some unpublished data) on QOL assessment tools and instruments that claim to measure quality of life in dementia. Literature for this review was identified by a thorough search of computer databases (1980-1997) that included Medline, Embase, PsychLit and International Pharmaceutical Abstracts. Reports concerning the conceptualisation, development, validation, reliability, reproducibility, comprehensiveness, practicality and use of QOL instruments in dementia/AD were selected for review as well as papers documenting clinical drug trials in this therapeutic area. A number of measures or methods used in the literature for assessing the quality of life of patients with dementing illnesses were identified. It was decided to present the resulting review in 2 parts that correspond to the 2 main groups into which the instruments were categorised. The first (part 1) looks at measures used to assess the impact of disease as well as instruments at a developmental or testing stage. The second (part 2) includes instruments that claim to measure quality of life in studies documenting the impact of a drug in this therapeutic area. There are as yet no validated methods of assessing the quality of life of both patients with dementia and their carers at the same time. QOL outcomes for these 2 groups is closely, if not fundamentally, linked and yet most studies identified in this review concentrate on measuring the quality of life of either the patient or the carer alone. Although some researchers may be getting close conceptually, an instrument has yet to satisfy all the criteria necessary to become accepted as a gold standard for QOL assessment in dementing illness. The ideal instrument must show that it can reliably, reproducibly and comprehensively assess quality of life for patients with dementia and their carers. It should also demonstrate that it can measure quality of life effectively using a practical administration technique that does not place any unnecessary burden on either informal carers, other healthcare workers involved or the patient themselves. Further cross-sectional and longitudinal research is required to psychometrically test the available instruments as well as continuing conceptual research to explore new ways of assessing quality of life in this important area.