Translation, Cultural Adaptation, and Validation of the Japanese eHealth Literacy Questionnaire Among Users in a Super-Aged Society: Mixed Methods Study.

Background: Japan is likely the world's leading aging society, and when leveraged effectively, digital health services hold great potential for addressing health care system challenges. Appropriate development and facilitation of these services require the evaluation of users' digital health literacy. However, the status of digital health literacy in Japan, especially among older adults, remains unclear, which limits efforts to effectively promote such services. Objective: This study aimed to translate the eHealth Literacy Questionnaire (eHLQ) into Japanese and test the translation's reliability. Additionally, it aimed to examine eHLQ scores among Japan's population, compare them across various backgrounds, and explore considerations for applying digital health systems to support Japan's aging society. Methods: A sequential exploratory mixed methods design was employed. The translation process prioritized achieving conceptual equivalence with the source language. To evaluate the translation's reliability, psychometric assessments by survey were conducted based on classical test theory and item response theory. Comparative statistical analysis was used to examine the impact of demographic factors. Results: A total of 504 individuals aged 18-88 years completed the survey, with 444 responding online and 60 in face-to-face interviews. The Japanese eHLQ showed good internal consistency, with Cronbach α values ≥0.78. The comparative fit index was >0.95, standardized root mean residual was ≤0.04, and standardized expected parameter change was ≤0.23, indicating good to acceptable fit. Item response theory analysis found adequate item location, discrimination, and factor loading. Boundary characteristic curve plotting demonstrated that all items fit well. Participants with more frequent digital health service use and better self-reported health status showed higher eHLQ scores across all 7 scales: (1) Using technology to process health information, (2) Understanding of health concepts and language, (3) Ability to actively engage with digital services, (4) Feel safe and in control, (5) Motivated to engage with digital services, (6) Access to digital services that work, and (7) Digital services that suit individual needs. Conclusions: The Japanese version of the eHLQ is robust and is likely to be a reliable and effective tool for assessing digital health literacy among Japan's population. There were no notable differences between scores of those aged above and below 65 years, or those with and without chronic disease(s). The findings also suggest that current systems may be tailored to frequent digital health users. The Japanese version of the eHLQ is expected to be used to effectively monitor digital health literacy in Japan's aging society.