Background: Mobile health (mHealth) apps are considered to be potentially powerful tools for improving lifestyles and preventing cardiovascular disease (CVD), although only few have undergone large, well-designed epidemiological research. “kencom” is a novel mHealth app with integrated functions for healthy lifestyles such as monitoring daily health/step data, providing tailored health information, or facilitating physical activity through group-based game events. The app is linked to large-scale Japanese insurance claims databases and annual health check-up databases, thus comprising a large longitudinal cohort. Objective: We aimed to assess the effects of kencom on physical activity levels and CVD risk factors such as obesity, hypertension, dyslipidemia, and diabetes mellitus in a large population in Japan. Methods: Daily step count, annual health check-up data, and insurance claim data of the kencom users were integrated within the kencom system. Step analysis was conducted by comparing the 1-year average daily step count before and after kencom registration. In the CVD risk analysis, changes in CVD biomarkers following kencom registration were evaluated among the users grouped into the quintile according to their change in step count. Results: A total of 12,602 kencom users were included for the step analysis and 5473 for the CVD risk analysis. The participants were generally healthy and their mean age was 44.1 (SD 10.2) years. The daily step count significantly increased following kencom registration by a mean of 510 steps/day (P<.001). In particular, participation in “Arukatsu” events held twice a year within the app was associated with a remarkable increase in step counts. In the CVD risk analysis, the users of the highest quintile in daily step change had, compared with those of the lowest quartile, a significant reduction in weight (–0.92 kg, P<.001), low-density lipoprotein cholesterol (–2.78 mg/dL, P=.004), hemoglobin A1c (HbA1c; –0.04%, P=.004), and increase in high-density lipoprotein cholesterol (+1.91 mg/dL, P<.001) after adjustment of confounders. Conclusions: The framework of kencom successfully integrated the Japanese health data from multiple data sources to generate a large, longitudinal data set. The use of the kencom app was significantly associated with enhanced physical activity, which might lead to weight loss and improvement in lipid profile.

Regular self-weighing is useful in obesity prevention. The impact of nudge-based occupational self-weighing programs in the cluster randomized controlled trial was examined. The primary outcome was regular self-weighing after 6 months, which we used to compute cost-effectiveness. Participants were Japanese local government employees who underwent 1 h workshops after being assigned to one of the three nudge groups. Each group was designed according to the nudges’ Easy, Attractive, Social, Timely framework: quiz group (n = 26, attractive-type nudges), implementation intentions group (n = 25, social-type nudges), and growth mindset group (n = 25, timely type nudges). A reference group (n = 36, no nudges) was also formed. After 6 months, all three interventions were effective for regular self-weighing, with the growth mindset intervention (60.0%) being significantly more effective. The cost-effectiveness of the growth mindset group was 1.7 times and 1.3 times higher than that of the quiz group and the implementation intentions group, respectively. Findings from our study are expected to facilitate the use of nudges for health practitioners and employers, which in turn may promote obesity prevention.

Objective: Prior research has implied that promoting sustaining physical activity through nudges is challenging and boosting health literacy is important for the long-term establishment of behaviors. This study aimed to investigate the effects of commitment-based health application on step count and health literacy. Methods: A control experiment was conducted involving employees from companies located in Shizuoka Prefecture, Japan. Participants were divided into three groups: the commitment app group (utilizing a commitment-based application "Minchalle," where teams of around five members were randomly assigned to declare a target step count and report daily step count with pictures), the self-commitment group (individuals declaring a target step count and endeavoring on their own), and the control group (no intervention). Changes in step count and health literacy were examined over one month. Results: A total of 109 employees from 7 companies participated. The changes in step count were an increase of 893 steps for the commitment app group, 243 steps for the self-commitment group, and 178 steps for the control group, with a significant increase in the commitment app group compared to the control group. Regarding health literacy measures, there was significant progress in four items out of five for the commitment app group compared to the control group, and significant progress in one item for the self-commitment group compared to the control group. Conclusion: Communication within the app teams, such as commitment, sharing photos of their goal achievements and provide encouraging comments to others, functioned as social nudges, suggesting the potential for an immediate increase in step count and long-term behavioral reinforcement through improved health literacy.

Purpose Follow-up examinations after health check-ups are important for early detection of noncommunicable diseases among workers. Nudging can serve as an effective intervention for individuals who avoid follow-up examinations due to cognitive biases. This study aims to evaluate the interest in nudge-based notification for follow-up examinations, targeting occupational health staff and undiagnosed workers in a randomized controlled trial. Methods Participants were randomly assigned to either a control group (receiving a text-based notification without nudges) or a nudge group (receiving a notification that modified the control group based on Easy-type nudges). An anonymous web survey was administered. Results Occupational health staff (n = 425) rated all items significantly higher, including “willingness to use the notification” which scored 2.22 for the control group vs. 3.62 for the nudge group on a 1- to 5-point scale (P < 0.001). Among undiagnosed workers (n = 871), there was no significant difference in “willingness to apply for the follow-up examinations” (3.01 vs. 3.09; P = 0.272), but all other items were rated significantly higher in the nudge group (P < 0.05). Conclusion Based on these findings, we suggest that occupational health staff should use nudge-based notifications. However, increasing the willingness of undiagnosed workers to undergo follow-up examinations remains challenging. To achieve this goal, it is necessary to incorporate multiple nudge elements into notifications.

To assess the effectiveness of promoting hand hygiene by nudges, the control experiment was conducted during the COVID-19 pandemic in Japan. Hand sanitizers were placed at entrances of health centers A (nudge group) and B (non-nudges/reference group). The users of each group were approximately 40 daily. In the nudge group, during week 1, the conventional notice was displayed. From weeks 2 to 4, sequential nudges based on the framework “MINDSPACE” were implemented: drawing an arrow on the floor towards a hand sanitizer, posting altruism messages, and providing trends in hand sanitizer usage. From weeks 5 to 8, no additional interventions were implemented. Until week 4, usage in the nudge group increased steeply. Although the gap narrowed after week 5, usage in the nudge group (1.7 times of week 1 usage) was higher than that in the reference group (1.4 times of week 1 usage) at week 8. The nudges cost 0.9 USD and were prepared within 3 hours. The series of nudges can be implemented with low cost and short preparation time, and the effect may last until week 8; these nudges will meet practitioners’ needs during the COVID-19 pandemic.

On January 20, 2023, the Japanese government announced easing the legal handling of the novel coronavirus disease 2019 (COVID-19) under its Infectious Diseases Control Act, effective May 8, 2023. While free vaccines will continue in fiscal year 2023, the future of mass vaccinations remains uncertain. The opt-out system, wherein local governments schedule vaccinations on behalf of the residents, may potentially alleviate issues associated with the currently adopted opt-in approach, such as procedural intricacies and scheduling difficulties, thereby facilitating the recovery of vaccination rates and simultaneously addressing vaccine wastage concerns. Given that COVID-19 still presents a substantial risk to specific groups, such as the elderly, recognizing the benefits of the opt-out system and the ethical and geographical challenges it poses is essential. With the collaboration of local governments and healthcare institutions, ongoing surveillance and scientific assessment are indispensable.