Fully Anonymized Digital Health Data Acquisition in a Research Partnership Using a Blinded Deidentification Proxy in the HerzFit App: Implementation Study

Background: The European General Data Protection Regulation (GDPR) strictly regulates the processing of personal and health-related data, posing challenges for digital health research, especially when data are collected using participants’ own devices. Although scientific data can theoretically be anonymized, standard internet communication protocols inevitably expose transmission metadata, preventing true anonymization. Existing solutions, including virtual private networks, reverse proxies, and trust centers, improve confidentiality but do not technically or legally enable fully anonymized data collection. Consequently, large-scale digital health research often requires extensive organizational measures, complex consent procedures, and high regulatory overhead. Objective: This study aimed to develop a GDPR-compliant concept for fully anonymized scientific data collection, ensuring that no entity has simultaneous access to identifying information and donated data. We also implemented and evaluated this concept in a real-world public-private partnership. Methods: We designed a data donation architecture based on a blinded deidentification proxy that decouples identifying transmission metadata from encrypted user data at the time of donation. The concept combines symmetric (Advanced Encryption Standard-128 in Cipher Block Chaining) and asymmetric (Rivest-Shamir-Adleman with Optimal Asymmetric Encryption Padding) encryption, enabling end-to-end encrypted and anonymized data transfer without persistent identifiers. The system was integrated into the HerzFit app, a mobile lifestyle coach for cardiovascular disease prevention available in German-speaking countries, and evaluated for adoption, technical feasibility, and performance. Performance overhead was assessed using round-trip time benchmarks. Duplicate donations were identified and merged to estimate unique data donors. Results: The solution was integrated and tested in the HerzFit app with more than 200,000 downloads between April 2022 and December 2025. Since the introduction of the data donation feature, more than 13,000 donations have been received, translating to more than 9000 individual users contributing anonymized datasets. Proxy-based transmission resulted in an average round-trip time of 143 ms, compared to 58 ms for direct transfer, representing a modest overhead while maintaining usability. The operator of the donation database did not gain access to identifying information at any stage, demonstrating full technical anonymization. The approach can be operated reliably at scale with minimal server resources due to the stateless proxy design. Conclusions: This work introduces a novel system architecture enabling fully anonymized, GDPR-compliant data donation directly from participants’ devices. By decoupling identifying metadata from encrypted health data, the concept minimizes regulatory effort, strengthens privacy protection, and provides a practical framework for large-scale digital health research in research partnerships, for example, between a private company and a research institution. The real-world deployment in HerzFit demonstrates the feasibility, scalability, and scientific utility of this approach. The concept is broadly transferable to other mobile health apps and has the potential to substantially expand ethically and legally compliant data acquisition.
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Impact of a Prototype Combining Recommender Functionality With Structured Documentation on Operator Performance in Calls to Medical Communication Centers: Quasi-Experimental Feasibility Study

<strong>Background:</strong> Management of contacts to medical communication centers relies heavily on clinical judgment, contextual understanding, and communication skills. Decision support systems, intended to complement medical expertise, may, due to their rigidity, impede effective caller interaction and may, together with the obligatory documentation of calls, contribute to a workflow that draws attention away from the communication. Recommender systems have demonstrated potential in supporting decision-making across various domains by nudging individuals toward better choices without undermining autonomy. We built a prototype that combined artificial intelligence–based question recommendations with structured documentation (hereafter: the prototype) and conducted a feasibility study to test its influence on operators’ performance. <strong>Objective:</strong> This study aimed to examine whether the prototype influenced the operators’ performance during telephone triage. We hypothesized that the prototype would affect medical quality without affecting communication quality. <strong>Methods:</strong> A quasi-experimental pre- and posttest feasibility study was conducted in a simulated setting. Twenty-five operators were voluntarily recruited from 5 Norwegian medical communication centers, in which 22 operators contributed to both the pretest (before the prototype) and the posttest (with the prototype). The operators handled the same 15 medical cases presented by simulated callers, with a 5-month interval between the 2 sessions. The question recommender was trained on other data and then fine-tuned on the 15 scenarios used. Audio recordings of the calls were rated using the tool Assessment of Quality in Telephone Triage. Pre- and posttest values were compared, with overall medical and communication quality as the primary outcomes. Secondary outcomes included specific items related to medical content and communication, accuracy of triage, patient safety, call duration, and efficiency. <strong>Results:</strong> A total of 320 paired calls were analyzed. Overall medical quality improved significantly with use of the prototype, from a mean of 6.83 points pretest to 7.16 points posttest rated on a 10-point scale (difference 0.34, 95% CI 0.11-0.57; <i>P</i>=.004). The effect size was small (Cohen <i>dz</i>=0.16). No significant change was observed in overall communication quality, with a mean of 7.06 points pretest and 6.97 points posttest (difference –0.09 points, 95% CI –0.28 to 0.10; <i>P</i>=.35). A significant decrease from pre‑ to posttest was observed in the specific items “Collects information about the patient’s location” (<i>P</i>&lt;.001) and “Ensures that the triage decision is understandable and feasible” (<i>P</i>=.002). None of the remaining secondary outcomes showed significant changes. <strong>Conclusions:</strong> The prototype yielded a modest improvement in medical quality within the scenario‑based test environment. Although overall communication quality remained unchanged, aspects of the interaction were negatively affected. Artificial intelligence–based question recommendations combined with structured documentation may serve as useful functionalities within a decision support system, but each functionality requires further testing and development before such technology can be implemented in the triage of unselected, real‑world calls. <strong>Trial Registration:</strong>

Examining the Influence of Social Network Factors on Weight Loss Among Latina and Non-Hispanic White Breast Cancer Survivors: Observational Cohort Study

<strong>Background:</strong> Breast cancer is the most commonly diagnosed cancer among women and is the leading cause of cancer death among Latina individuals. Breast cancer survivors are at increased risk of obesity. Mobile health interventions have been shown to be an effective way of reducing the risk of weight gain. Less studied but also important is the extent to which social networks play a role in supporting or undermining weight loss efforts. <strong>Objective:</strong> We examined the association between 4 kinds of social network interactions and change in BMI among Latina and non-Hispanic White breast cancer survivors engaging in a mobile health app pilot study. <strong>Methods:</strong> Latina and non-Hispanic White breast cancer survivors were randomized to engage in either the <i>Mi Salud</i> or <i>Mi Vida, Mi Salud</i> app. <i>Mi Salud</i> allowed participants to engage in self-monitoring by recording their behaviors and symptoms. <i>Mi Vida, Mi Salud</i> used these same features in addition to a self-discovery feature that would summarize and report back this information to participants. We collected information on BMI and health-related social support; positive and negative health-related social control (which included persuasion and pressure, respectively); and undermining at baseline and after 12 weeks of the intervention. <strong>Results:</strong> While participants (non-Hispanic White n=22 and Latina n=22) in both study arms experienced decreased BMI over the 12-week period, this change in BMI did not differ according to ethnicity. Furthermore, change in social support was not associated with decreased BMI (B=−0.19, <i>P</i>=.12). However, the interaction between change in social support and ethnicity was significant, such that predicted margins were significant for non-Hispanic White individuals (B=−0.57, <i>P</i>=.02) but not for Latina individuals (B=−0.54, <i>P</i>=.72). Change in persuasion was not associated with change in BMI (B=0.072, <i>P</i>=.61); however, increased pressure was associated with increased BMI (B=0.66, <i>P</i>=.02). Finally, change in undermining was not associated with change in BMI (B=0.32, <i>P</i>=.11). <strong>Conclusions:</strong> Latina and non-Hispanic White participants did not differ in weight loss. However, our findings regarding social network involvement and change in BMI show the importance of considering social network processes in weight loss among breast cancer survivors. These findings buttress existing research suggesting the benefits of social support, particularly within specific cultural frameworks, while attempts to increase participants’ healthy behaviors that involve criticism can be detrimental to change efforts. Future research that builds on these findings is needed to elucidate the specific social network processes that may drive health behavior among diverse breast cancer survivors.

Digital Therapeutic Content for Substance Use Disorder Treatment: Development and Evaluation Study

Background: Substance use disorders (SUDs) are a major public health concern, contributing to significant individual and societal costs. Despite this, the uptake of evidence-based pharmacologic and behavioral interventions remains limited. The digital delivery of SUD treatment has emerged as a potentially scalable way to reduce access barriers and increase treatment use. Existing digital therapeutic interventions are often created without clinician involvement, evidence-based materials, interdisciplinary input, or content review. The implementation of a structured and methodologically rigorous development process is needed across digital health interventions to help ensure patient-facing materials are validated, understandable, and actionable for the end user. Objective: This early report seeks to describe and evaluate an iterative, interdisciplinary, platform-agnostic process for adapting and refining existing print materials for digital therapeutic modules in SUD treatment. The a priori goal was to evaluate if a structured, human-centered approach would generate digital modules that were rated as understandable and actionable based on a validated assessment for written materials. Methods: Fourteen therapeutic modules were adapted from existing Mayo Clinic–written, patient-facing education materials originally developed by a board-certified addiction psychiatrist and a doctoral-level education specialist for clinical use. A team of 4 purposively recruited licensed alcohol and drug counselors with lived experience with a SUD, all in recovery, and a doctoral-level therapeutic specialist met weekly for one hour over a 6-month period to iteratively adapt this existing content for smartphone delivery (2‐3 hours per module). The process flow included selecting source material, restructuring content for viewing on a phone screen, simplifying language, improving organization and flow to promote understanding, and including specific actions users could take based on the content. The counselors then independently evaluated the modules using the Patient Education Materials Assessment Tool for printable materials (PEMAT-P). PEMAT-P scores for understandability and actionability were calculated as percentages, and descriptive statistics were used to summarize scores in aggregate and across modules. A target of >70% was set for each PEMAT-P domain, consistent with accepted benchmarking standards. Results: Mean understandability and actionability for all modules were 87.2% (SD 4.8%; range 81.4%‐96.9%) and 75.1% (SD 12.3%; range 57.1%‐95.0%), respectively, exceeding the recommended threshold. While all modules were adequately understandable, 35.7% (5/14) scored below the actionability threshold. Conclusions: This early report highlights the value of a human-centered, iterative process for adapting therapeutic materials for digital delivery in SUD treatment. Although the modules performed well overall on PEMAT-P benchmarks, actionability was less consistent than understandability, and aggregate scores masked weaknesses in several individual modules. This indicates that a standardized process does not guarantee actionable material across all content types. Involving current patients in this process may improve the end product by incorporating a perspective that was previously missed.

A Sustainable Lifestyle Intervention Among Office Workers: Cluster Randomized Pilot and Feasibility Study

Background: Society faces multiple challenges, including lifestyle diseases and global climate change. Framing health education within sustainable development may enhance motivation for behavior change because proenvironmental behaviors, as well as healthy behaviors, often rely on the same behavior change principles. Combining these perspectives may therefore reinforce health behaviors and climate-friendly choices. Objective: This pilot study aims to explore changes in dietary intake, diet-related carbon footprint, and physical activity among office workers receiving sustainable plus healthy lifestyle (sustainable lifestyle arm) or healthy lifestyle education (healthy lifestyle arm) alone. It also aims to assess the feasibility of the intervention functions, including workshop attendance rate, participants’ dietary goals, social support, and facilitators and barriers to behavior change. Methods: A 2-armed participant-blinded cluster randomized study, including an experimental intervention arm (sustainable lifestyle; n=19) and a control intervention arm (healthy lifestyle; n=14), was conducted in Sweden. The study lasted 8 weeks and included 6 workplace-based workshops and was framed by the behavioral change wheel and the socioecological model. Diet, carbon footprint, and physical activity were assessed using the web-based questionnaires Meal-Q and Active-Q. Attendance rate, individual goals, social support, and facilitators and barriers were assessed using printed questionnaires. Results: The reduction of total diet-related carbon dioxide equivalents (COe) was 0.8 kg and 0.4 kg per day for the sustainable and healthy lifestyle arm, respectively. Also, there was a statistically significant interaction between time and lifestyle when the carbon footprint was expressed as a qualitative aspect of diet, that is, COe kg per 1000 kcal per day (=.05). Moreover, the intake of vitamin C, a marker for fruits and vegetables, increased to 8.0 and 12.5 mg per 1000 kcal per day for the sustainable and healthy lifestyle arms, respectively. In addition, total sedentary time decreased by 0.4 hours per day in the sustainable lifestyle arm, but not in the healthy lifestyle arm. This indicates that the educational workshops in respective arms had different impacts on health behavior over time. Minor differences were found in dietary goals, with the sustainable lifestyle arm setting more goals related to ecological and vegetarian foods. No differences were seen between arms regarding barriers or facilitators. Conclusions: This study suggests that embedding healthy lifestyle recommendations within a sustainable development context may be an efficient way to reduce carbon footprint and increase healthy behavior among office workers. Given the ongoing global epidemic of metabolic diseases, climate change, and environmental degradation, promoting a sustainable lifestyle in a workplace context has the potential to counteract these trends. Trial Registration: ClinicalTrials.gov NCT06698094; https://clinicaltrials.gov/study/NCT06698094
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Barriers and Facilitators in the Implementation of the Systematic Medical Appraisal, Referral, and Treatment (SMART) Mental Health Digital Intervention in Rural India: Mixed Methods Process Evaluation Study

<strong>Background:</strong> An estimated 150 million people have mental health care needs in India, but only 15% are able to access care. Depression and anxiety contribute to a large proportion of mental morbidity. The Systematic Medical Appraisal, Referral, and Treatment (SMART) Mental Health trial used a mobile-based clinical decision support system for primary care doctors and community health workers (CHWs) to identify and treat people at risk of depression, anxiety disorders, and self-harm. A community-based antistigma campaign was also delivered. The intervention led to improved remission rates for depression and anxiety and lower stigma scores. <strong>Objective:</strong> A process evaluation assessed (1) implementation fidelity, barriers, and facilitators; (2) perceptions of doctors and CHWs on the use of SMART Mental Health; and (3) the causal pathways that led to trial outcomes. <strong>Methods:</strong> A mixed methods evaluation combining backend program data and qualitative data was conducted. A total of 38 focus group discussions and 37 key informant interviews were conducted with primary doctors, CHWs, government officials, local community leaders, and research project staff. The data were coded and analyzed using a framework analysis approach based on the UK Medical Research Council guidance on process evaluations and the Reach, Effectiveness, Adoption, Implementation, and Maintenance framework. <strong>Results:</strong> The intervention had high implementation fidelity. Across clusters, the median proportion of participants with at least 1 CHW follow-up was 98% (IQR 96.6%-100%). The referral rate for a psychiatrist was low (224/1697, 13.2%), and only 23.6% (53/224) of those referred visited the psychiatrist. The median exposure to antistigma audiovisual content was 84% (IQR 65.7%-95.9%). At the community level, key implementation barriers included cultural inhibitions in seeking mental health care and the unavailability of patients due to competing demands. Proximity and tight social connections between CHWs and their communities were important facilitators in seeking medical help. Doctor and CHW training, mentoring, and feedback provided by program staff were important facilitators to support the use of the digital health components by the health workforce. <strong>Conclusions:</strong> A complex intervention that included both community-based antistigma and clinical digital health interventions achieved high implementation fidelity. Key areas to consider for maintenance of such interventions include (1) the need for sustained community-based strategies to address stigma and other cultural barriers; (2) health workforce strengthening policies, including supportive supervision for CHWs and doctors to increase capability in the use of mental health digital health tools; and (3) strategies to improve access to specialist care for those with more complex care needs. <strong>Trial Registration:</strong> Clinical Trial Registry India CTRI/2018/08/015355; https://tinyurl.com/5r63suxp