Development and evaluation of a short version of the quality of life questionnaire for dementia

Background: There are many quality of life (QOL) instruments for evaluating dementia patients. The QOL questionnaire for Dementia (QOL-D) is one of such instruments and a validated objective measure of QOL for patients with dementia. It comprises 31 items encompassing six domains. However, with 31 items, its length is a disadvantage. The purpose of this study was to develop a short version of QOL-D (short QOL-D). Methods: We used data from two studies. The participants were 264 inpatients with dementia in the first sample and 395 outpatients at a memory clinic in the second sample. We used maximum likelihood factor analysis with promax rotation to reduce the number of items. Results: We produced a nine-item version of QOL-D (short QOL-D) with positive (six items) and negative (three items) dimensions. The correlation coefficients of short and total versions of QOL-D were 0.892-0.918 for total scores, 0.903-0.936 for positive dimension scores, and 0.788-0.837 for negative dimension scores. Total short QOL-D scores showed a significant correlation to the Geriatric Depression Scale score and the apathy score of the Neuropsychiatric Inventory. Conclusions: The short QOL-D produced results comparable with that of the full version. Reducing the number of items may make administration of the instrument easier.