Linguistic and Psychometric Validation of the Cognition Bolt-On Version of the Japanese EQ-5D-5L for the Elderly.

Abstract

The need for a cognition bolt-on version of the EQ-5D, which would capture cognitive impairment by adding a dimension to the generic instrument assessing health status, has been increasing in Japan. To develop a cognition bolt-on version of the 5-level EQ-5D (EQ-5D-5L+C), we linguistically validated a cognition dimension and psychometrically validated the EQ-5D-5L+C. Following linguistic validation of the cognition dimension, psychometric validation of the EQ-5D-5L+C proxy version utilized anonymized data collected from nursing home residents between October 2021 to April 2022. The validity, reliability, and sensitivity to change were evaluated. Data from 254 participants, including the finalized Japanese EQ-5D-5L+C proxy version, were analyzed for the psychometric validation. Mean (±standard deviation) age and Mini-Mental State Examination (MMSE) scores were 87.14±7.29 years and 15.76±8.46, respectively. The correlation was strongest between the cognition dimension and MMSE scores (rs = -0.640). Test-retest reliability was good in the cognition dimension in both baseline and two-time points (3 months: k = 0.644; 6 months: k = 0.656). Although a correlation between changes in the cognition dimension and those in the MMSE score from baseline was weak (3 months: rs = -0.191; 6 months: rs = -0.267), a correlation with changes in the MMSE score was higher when the cognition dimension was added compared to the EQ-5D alone (3 months: rs = -0.142 versus rs = -0.074). The Japanese EQ-5D-5L+C proxy version developed is a valid tool that captures health status including cognitive function, with a consideration for an over-time assessment. The benefits in adding the cognition dimension to the EQ-5D-5L to assess health state were suggested.