This study reports selected findings from a project commissioned by the Kanagawa Prefectural Government. Between April 1, 2020, and July 31, 2023, a cumulative total of 186,972 individuals registered as users; 10,239 aged ≥18 years who accessed the ME-BYO index at least once were included in the analysis.

The ME-BYO index is a self-reported 15-item assessment of metabolic, locomotor, cognitive, and mental resilience domains. Scores range from 0 to 100, with higher scores indicating better health [2] (Multimedia Appendix 1).

Differences between 1-time and repeat users were tested using t tests (continuous variables) and chi-square tests (categorical variables). Logistic regression examined the association between engagement (1-time users as reference) and independent variables (sex, age, and domain scores). Analyses were performed using Stata 17 SE (StataCorp). Further details are provided in Multimedia Appendix 1.

This study was approved by the Institutional Review Board of the Kanagawa Cancer Center (2024Eki-108). Informed consent was waived as only anonymous data were analyzed. No compensation was offered. The My ME-BYO Record app is freely available, and users consent to the Kanagawa Prefectural Government’s Terms of Use upon registration [4].

Approximately 20% (n=2202) of users were repeat users, indicating repeat engagement with the ME-BYO index for health monitoring was low. Although engagement may increase over time, the Prefectural Government may struggle to incorporate the app into regional health strategies until such growth occurs.

Repeat users were older than 1-time users. Users of mHealth apps supporting self-care and chronic disease monitoring also tend to be older than nonusers [5]. Older individuals may view the free ME-BYO index feature as a useful tool for monitoring well-being, leading to repeat engagement [6,7].

Repeat users also had lower ME-BYO index scores, particularly in cognitive function. As the app displays the latest ME-BYO index score on the home screen, repeat users may be motivated by disappointment with low scores and continue using the app to improve them [6]. Conversely, 1-time users might worry that subsequent scores would be worse. Lower cognitive ability has been associated with reduced mHealth access [8], yet individuals with chronic conditions are more likely to use mHealth apps than those without [9]. Our findings suggest that this app may help manage cognitive function in those with poorer cognitive abilities.

Repeat users also had higher locomotor function scores. Physically active individuals are more likely to use mHealth apps to manage health behaviors [9]. Similarly, those with better mobility may perceive the app as more useful for health monitoring, encouraging active engagement [7].

First, most app users were aged older than 40 years, limiting the generalizability of our findings to younger age groups. Second, there is potential for reporting bias through self-report. Although the Mini-Cog and walking speed measures in the ME-BYO index have been validated [10,11], other components still require validation. Third, the dataset lacked details such as disease comorbidities and socioeconomic status, which may affect user engagement. Including these confounders in future studies will improve the interpretation of the findings.

This study highlights a gap between 1-time and repeat engagement with the ME-BYO index for health monitoring. Using a real-world database, our findings may help inform strategies to improve engagement.