The impact of subject/respondent characteristics on a proxy-rated quality of life instrument for the Japanese elderly with dementia.

The development of a quality of life (QL) instrument for evaluating quality of services requires extensive validation. This study examines the impact of subject/respondent characteristics on a newly developed quality of life instrument for the Japanese elderly with dementia (QLDJ) as a part of the validity examination. In the QLDJ, QL is defined as a three-dimensional construct: 'interacting with surroundings', expressing self', and 'experiencing minimum negative behaviors'. Thus the QLDJ is a multi-dimensional, 24-item instrument, and it is answered by a proxy, the formal caregiver (respondent) because the elderly with severe dementia cannot be directly interviewed. Altogether 623 elderly persons experiencing dementia from 37 institutions (e.g., nursing homes, day care centers) in Japan were assessed using the QLDJ by their formal caregivers. In addition to the levels of dementia and independence in activities of daily living, factors such as gender of the elderly person and respondent, elderly person's age, participation in recreational activities, qualification of the respondent were significantly associated with 'interacting with surroundings' and 'expressing self'. The levels of dementia and independence as well as qualification of the respondent were associated with 'experiencing minimum negative behaviors'. Possible reasons for these associations and how to deal with them are discussed. Careful control for those factors is needed when the QLDJ is used in future research.