Background: Although QOL is an important indicator to assess multiple facets of life, the QOL of Alzheimer's disease (AD) subjects with impaired cognitive ability due to dementia has not yet been fully investigated. In this study, we developed the Japanese version of the Quality of Life-Alzheimer's disease (QOL-AD) scale by means of back-translation, and ascertained its reliability and validity for evaluating the quality of life in AD subjects. We also hypothesized that the presence of neuropsychiatric symptoms may determine the characteristics and determinants of both the patients' and the caregivers' responses to the patients' QOL questionnaire.
Methods: We administered the QOL-AD questionnaire to subjects with mild or moderate AD (n = 140). The test-retest reliability was evaluated by the same interviewer after a month's interval. Data from the following tests were also collected to ascertain the validity of the questionnaire: Short Memory Questionnaire (SMQ), Neuropsychiatry Inventory (NPI), Hyogo Activities of Daily Living Scale (HADL) and Mini-Mental State Examination (MMSE).
Results: The Japanese version of the QOL-AD questionnaire demonstrated good internal reliability for both the patients' (Cronbach's alpha = 0.84) and the caregivers' responses (Cronbach's alpha = 0.82) and good test-retest reliability for both the patients' (intraclass correlation coefficient = 0.84) and caregivers' reports (intraclass correlation coefficient = 0.91). The concordance between the patients' self-report and the caregivers' observation was moderate (Pearson correlation coefficient = 0.60). The score for the 'mood factor' (apathy, depression/dysphoria) in NPI predicted the overall QOL score as determined from both the patients' and the caregivers' responses for subjects with mild (MMSE>or=21, n = 88) and moderate (MMSE< 21, n = 52) AD. The score for the 'psychosis factor' (delusions, hallucinations, anxiety, agitation, disinhibition, irritability, aberrant motor activity) in NPI predicted the total QOL score as determined by the patients and the caregivers among subjects with moderate AD only.
Conclusions: As hypothesized, the presence of neuropsychiatric symptoms may be an important predictor of both the patients' and caregivers' responses to the patients' QOL questionnaire. QOL-AD appears to be a promising measure of the QOL of subjects with mild to moderate AD in Japan.