Development and validation of the Japanese version of the Death Literacy Index (DLI‐J) and its short form (DLI‐J‐9)

Aim To translate, culturally adapt, and psychometrically validate the Japanese version of the Death Literacy Index (DLI‐J) and its short‐form version (DLI‐J‐9) to assess death literacy among Japanese adults. Methods A multiphase mixed‐methods design was employed. The process included forward translation, reconciled single translation, back translation, translation review, cognitive interviews ( n = 8), and psychometric validation using a nationally representative online sample of 2500 Japanese adults aged 20–79 years. Participants completed an online survey, with a subsample ( n = 300) completing a retest after 4 weeks. Confirmatory factor analysis (CFA), internal consistency, construct validity, and test–retest reliability were evaluated. Results The DLI‐J demonstrated excellent psychometric properties. CFA supported the six‐factor structure of the DLI‐J (Tucker–Lewis index [TLI] = 0.940, comparative fit index [CFI] = 0.947, standardized root mean square residual [SRMR] = 0.048, and root mean square error of approximation [RMSEA] = 0.063) and the two‐factor structure of the DLI‐J‐9 (TLI = 0.945, CFI = 0.960, SRMR = 0.042, and RMSEA = 0.069). Internal consistency was excellent for the total DLI‐J scale ( α = 0.959) and all subscales ( α = 0.870–0.959). Convergent validity was supported by positive correlations with death competency, whereas discriminant validity was confirmed by negligible correlations with loneliness. Known‐groups validity was established, with higher scores among bereaved individuals and end‐of‐life care professionals. The test–retest reliability was moderate to good (intraclass correlation coefficient [ICC] = 0.515–0.819). The overall DLI‐J mean score was 3.82 (standard deviation = 1.91), lower than international benchmarks. Floor effects were observed in the hands‐on care, accessing help, and community support subscales. Conclusion The DLI‐J and DLI‐J‐9 are psychometrically robust instruments for assessing death literacy.