Evaluation of the quality of life in dementia with a generic quality of life questionnaire: the Duke Health Profile

OBJECTIVE: The study was designed to determine the acceptability, feasibility and validity of measuring quality of life in a representative sample of dementia patients with a generic instrument, the Duke Health Profile. METHOD: The French version of the Duke Health Profile was administered to 148 subjects with a mental disorder according to the DSM-III-R diagnostic criteria. The feasibility and acceptability of employing the instrument were determined by the refusal rate, the type of administration, and the percentage and distribution of missing data. Reliability was determined with Cronbach's alpha coefficient. Instrument reproducibility was assessed with the intraclass correlation coefficient for test-retest values. Internal construct validity was determined by factor analysis. Discriminant capacity was determined by comparing the average scores on each measure among patients with and without an additional chronic pathology. The measurements obtained were compared by source of information (patient, family proxy and care provider proxy). RESULTS: The feasibility and acceptability of the instrument was good. Only 2% of the patients refused to complete the questionnaire. Help from the interviewer was necessary in 79% of the cases. The average completion time was 10.6 min. Missing data exist in only 3.5% of the cases on average, except among patients with severe dementia (Mini Mental State Examination <10). For reliability, internal consistency was acceptable (Cronbach's coefficient alpha = 0.5--0.7) when the self-esteem (0.23) and social health (0.26) concepts were eliminated. Reproducibility as measured by test-retest scores was moderate to good (intraclass correlation coefficient r = 0.53--0.80), except for anxiety (0.48) and perceived health (0.45). Severity of dementia mainly affected the feasibility, acceptability and reproducibility of the instrument. The family proxy seemed to agree more with the patient than did the care provider proxy. CONCLUSION: Quality of life can be measured in patients with dementia, but special tools need to be developed for severe dementia.