Measuring functional health among the elderly: development of the Japanese version of the World Health Organization Disability Assessment Schedule II.

The Japanese version of the World Health Organization Disability Assessment Schedule II (WHODAS II-J) was developed and its psychometric properties were evaluated, and then used to determine the influence of disability on quality of life among the elderly in Japan. The study included three phases: qualitative, preliminary and field. For the qualitative portion of the study, six key informants were interviewed before the translation/back-translation procedure. For the preliminary study, 17 healthy elderly individuals were interviewed using the 12-item interview version of the WHODAS II-J. For the field study, different versions of the WHODAS II-J and the Japanese version of the World Health Organization Quality of Life BREF (WHOQOL-BREF) were tested with different participants (the 36-item interview version with 30 participants living in a nursing home, the 36-item proxy version with 30 caregivers working in the nursing home, and the 12-item and 36-item self-report versions with 132 and 129 healthy elderly living in Kanto and Kinki regions, respectively). In total, 321 elderly individuals participated in the field study. Of these participants, physical or mental disabilities were present in 47. Cronbach's α scores calculated for each of six domains of the WHODAS II ranged from 0.67 to 0.98. A significant correlation was observed between the results of the WHODAS II-J and the degree of disability (P<0.01), and a negative correlation was observed between WHOQOL-BREF and WHODAS II-J scores (P<0.01). A significant difference was found between healthy elderly individuals and those with disabilities in three domains: getting around, self-care, and life activities (P<0.01). In conclusion, the WHODAS II-J is a reliable and valid instrument for assessment of function in the elderly population in Japan.