This single-center, 2-arm, parallel-group RCT with a 1:1 allocation ratio will be conducted at the Health Management Center of the First Affiliated Hospital of Sun Yat-sen University in Guangzhou, China (Figure 1). The trial is designed within a superiority framework to determine whether the CardioCare system is more effective than minimal usual care in achieving triple risk factor control at 12 months among high-risk adults.

Eligible participants will be aged ≥50 years, have an estimated 10-year CVD risk greater than 10% calculated using the Guangzhou Biobank Cohort Study (GBCS) model [13], have no previous diagnosis of CVD, and own a mobile device capable of receiving messages from the CardioCare system. The GBCS model has been validated in a large urban Chinese cohort and is appropriate for identifying high-risk individuals in this population [13]. Participants must reside in Guangzhou for the duration of the study and provide written informed consent. Individuals will be excluded if they have severe comorbidities that preclude regular follow-up in the judgment of a study clinician based on medical record review, a life expectancy of less than 1 year, recent participation in similar CVD management programs, or any other condition judged by the investigators to interfere with safe participation.

A statistician not involved in participant recruitment will generate the random allocation sequence using computer-generated random numbers. Randomization will be stratified by sex, with random block sizes ranging from 4 to 12 undisclosed to the recruitment team to ensure unpredictability. Allocation concealment will be maintained using sequentially numbered opaque, sealed envelopes prepared by staff independent of the enrollment process.

Research assistants will identify eligible participants, send invitations, and obtain informed consent, after which the next available envelope will be opened to reveal allocation. Personnel enrolling participants will not have access to the allocation sequence.

Participants and care providers will not be blinded due to the nature of the intervention. Outcome assessors and statisticians will remain blinded to allocation. Group codes will be masked during analysis, and the randomization key will only be revealed after the primary analysis is completed. No emergency unblinding procedures are required given the nonpharmacological nature of the intervention.

The CardioCare system uses a structured message-tailoring algorithm that integrates clinical data, participant risk profiles, and previous engagement records to personalize message content and frequency. Cardiologists oversee message template development and conduct monthly reviews to ensure clinical relevance and appropriateness. Participant engagement is continuously monitored through automated system logs, which record message delivery and interaction. Predefined engagement thresholds trigger alerts to research staff for follow-up support. This operational framework follows the Template for Intervention Description and Replication guidance for intervention specification, ensuring reproducibility and transparency in intervention delivery.

The intervention group will receive a personalized intervention from the CardioCare system for 12 months. This system integrates CVD risk stratification using the GBCS model with tailored weekly SMS text messages or WeChat messages covering medication adherence, diet, exercise, and follow-up reminders. Messages will be reviewed by a cardiologist before dispatch and customized based on each participant’s clinical profile and previous engagement. Message types will vary in intensity and content (eg, motivational, educational, or reminder based) depending on previous adherence and risk level. All messages are logged automatically, and participant engagement (eg, message reads, replies, and link clicks) is continuously monitored. Participants with declining engagement will be flagged for follow-up by the research assistant team, ensuring responsiveness. Cardiologist review takes place monthly or upon significant clinical change using an internal dashboard linked to participant records.

The control group will receive minimal usual care, consisting of notification of health checkup results and general recommendations to seek outpatient follow-up if indicated. After completing the 12-month follow-up, control group participants will be offered access to the CardioCare system. Participants may discontinue the intervention at any time or if advised by the study physician. No restrictions will be placed on concomitant medical care.

The primary outcome is the proportion of participants achieving simultaneous control of blood pressure, lipids, and glycemia at 12 months, defined as SBP of <130 mm Hg and diastolic blood pressure of <80 mm Hg, LDL-C of <2.6 mmol/L, fasting plasma glucose of <7.0 mmol/L, and HbA_1c of <7% (Table 1). Secondary outcomes include (1) clinical measures (changes in estimated 10-year CVD risk [GBCS model]; mean changes in SBP, LDL-C, triglycerides, fasting plasma glucose, and HbA_1c; and the proportion achieving control of individual risk factors at 12 months), (2) behavioral measures (medication adherence and adoption of lifestyle modifications), (3) system-level outcomes (participant engagement with the CardioCare system and usability and satisfaction among participants and physicians), and (4) economic outcomes (incremental cost-effectiveness expressed as cost per participant achieving triple risk factor control and per quality-adjusted life year [QALY] gained; Table 1).

Medication adherence and lifestyle modifications (diet, physical activity, and smoking) will be assessed using structured questionnaires adapted from previously validated tools applied in chronic disease studies in Chinese populations. Measurements for all primary and secondary outcomes will be taken at baseline and 6 and 12 months after enrollment. To assess feasibility and acceptability, we will evaluate (1) recruitment rate (participants enrolled and approached); (2) retention rate at 12 months; (3) system engagement metrics, including number of messages opened and responded to; and (4) participant-reported usability and satisfaction at 12 months. Usability will be assessed using the System Usability Scale, and satisfaction will be measured using a 5-point Likert scale. These data will inform scalability potential and guide future implementation strategies. Quantitative feasibility metrics will be summarized descriptively, and comparisons between groups will be exploratory.

In addition to formal clinical and behavioral assessments at baseline and 6 and 12 months, the CardioCare system captures weekly engagement data, including message delivery, read status, interaction frequency, and responsiveness. These metrics will be used to construct engagement trajectories and assess temporal patterns of system use. The economic evaluation will be conducted from the health care system perspective. Direct medical costs will include personnel time, digital intervention costs (eg, system maintenance and messaging), outpatient visits, medications, and laboratory tests. Cost-effectiveness will be assessed through incremental cost-effectiveness ratios reported as cost per participant achieving triple risk factor control and per QALY gained.

The sample size was calculated to detect an absolute difference of 15 percentage points in the primary outcome (ie, 20% in the control group vs 35% in the intervention group), with 80% power and a 2-sided α of .05. This requires 126 participants per arm. Allowing for 15% attrition, the final target sample size is 300 participants (150 per group). This expected difference is based on previous studies in Chinese older adult populations showing triple risk factor control rates ranging from 15% to 25% under usual care and on effect sizes from similar multicomponent digital interventions, which have reported 10– to 20–percentage point improvements in risk factor control [14]. Recruitment will take place during routine health checkup visits, with eligible individuals identified from their health data and approached in person by a trained research assistant. Additional recruitment will be supported through study posters in the Health Management Center and announcements on the hospital’s WeChat platform.

Clinical and laboratory measurements will be collected at baseline and 6 and 12 months using standardized procedures. Blood pressure will be measured in duplicate using validated automated devices after 5 minutes of rest; the average reading will be recorded. Lipid profiles and glycemia will be measured in fasting venous samples analyzed at the hospital’s certified laboratory. Medication adherence will be evaluated using a self-administered online questionnaire. Lifestyle modification and system engagement data will be collected through structured questionnaires. All data will be entered into a secure, password-protected database, and automated range checks will be conducted. Regular audits will be conducted to ensure accuracy. Personal identifiers will be stored separately from trial data accessible only to authorized personnel.

All analyses will follow the intention-to-treat principle, with all randomized participants included in the group to which they were assigned. The primary outcome will be compared between groups using a chi-square test, with risk differences and 95% CIs calculated. Secondary continuous outcomes will be analyzed using mixed-effects models adjusting for baseline values. Missing data patterns will be assessed visually and statistically (eg, the Little missing completely at random test) to inform appropriate imputation models. Multiple imputation using chained equations will be used under the assumption of the data being missing at random, and sensitivity analyses will include complete-case and worst-case scenarios. Prespecified subgroup analyses will examine potential effect modification by sex, age group, and baseline CVD risk. These subgroup analyses are exploratory in nature and will not be powered to detect statistically significant differences. Findings will be interpreted descriptively and used to inform hypothesis generation for future trials.

QALYs will be estimated using utility weights derived from published data on health-related quality of life in Chinese adults. A within-trial cost-effectiveness analysis will be conducted over the 12-month intervention period. Sensitivity analyses will be conducted to examine the robustness of the incremental cost-effectiveness ratio to variations in key cost and outcome inputs. All analyses will be conducted using Stata (version 18.0; StataCorp). A 2-sided P value of <.05 will be considered statistically significant.

A data monitoring committee comprising independent epidemiologists and cardiologists will oversee trial conduct, review adverse events, and provide recommendations regarding trial continuation. No interim analyses or formal stopping rules are planned. The trial will be monitored monthly by the study management team to ensure protocol adherence. The data monitoring committee will make recommendations regarding trial continuation or necessary modifications. Oversight procedures will follow International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use good clinical practice guidelines.

Ethics approval has been obtained from the institutional review board of the School of Public Health, Sun Yat-sen University (2024-110). Written informed consent will be obtained from all participants by trained research assistants. Protocol amendments will be submitted to the institutional review board and communicated to trial staff and, if necessary, participants. Confidentiality will be maintained by assigning unique study IDs, with personal information stored separately from trial data. After the trial, control participants will receive access to the CardioCare system for 12 months. Participants who experience harm related to trial participation will receive appropriate medical care and compensation according to institutional policy.

CVD remains the leading cause of morbidity and mortality in China, particularly among older adults. Although the NBPHSP has greatly expanded access to routine health checkups, postscreening management of chronic conditions such as hypertension, dyslipidemia, and diabetes is often suboptimal [16]. The CardioCare system was designed to address these gaps by integrating CVD risk prediction, personalized health management, and continuous digital engagement into existing health care workflows. This RCT will be the first to evaluate whether such a system can improve simultaneous control of blood pressure, lipids, and glycemia among high-risk older adults in China.

This RCT has several strengths. First, it addresses a critical gap in postcheckup care by focusing on triple risk factor control, a clinically meaningful composite end point closely linked to CVD outcomes. Second, the intervention is built on an established risk prediction model (the GBCS model) and combines risk communication and evidence-based lifestyle and medication adherence strategies with personalized digital communication. Third, integration into an existing health checkup center ensures feasibility in a real-world setting, and the trial includes cost-effectiveness analysis to inform potential scalability.

There are also potential limitations. This trial is conducted in a single urban health management center, which may limit generalizability to rural or resource-limited settings where infrastructure and cardiovascular risk management practices differ. However, as an initial trial of the CardioCare system, this setting enables evaluation under conditions of high intervention fidelity. Future studies will be needed to assess adaptations for broader populations, particularly in underresourced areas or settings with lower digital capacity. The reliance on self-reported measures for some behavioral outcomes, such as medication adherence and lifestyle modification, introduces the possibility of reporting bias. Engagement with the digital intervention may vary between participants, potentially influencing its effectiveness. In addition, while the triple risk factor control outcome is clinically relevant, it may be more challenging to achieve than improvements in individual risk factors, potentially underestimating the system’s benefit. If the trial demonstrates effectiveness, the CardioCare system could be scaled to other health checkup centers and integrated into national health programs, potentially improving chronic disease management for millions of older adults. Although mobile device access and digital communication literacy are eligibility requirements, these are unlikely to be significant sources of exclusion in the Chinese context, where smartphone ownership and WeChat use exceed 99% among Guangzhou residents, including those over the age of 50 years. Future research could explore adaptations for rural settings, automation of message delivery, integration with other chronic disease management modules, and long-term effects on CVD events and mortality. Finally, as the trial is conducted within a single health management center, there is a potential for contamination between intervention and control participants. Although the CardioCare intervention is delivered individually via private digital communication and participants do not engage in group sessions, the possibility of informal information sharing cannot be entirely excluded.

This RCT will evaluate the effectiveness of the CardioCare system, a digital cardiovascular management platform, in achieving simultaneous control of blood pressure, lipids, and glycemia among high-risk adults identified through routine health checkups. By integrating established risk prediction with personalized health management and continuous digital engagement, the intervention aims to address critical gaps in postscreening care within the Chinese health care system. The findings will provide robust evidence on both the clinical impact and cost-effectiveness of the CardioCare system, informing its potential for large-scale implementation in health checkup centers and integration into national chronic disease prevention strategies. If effective, the CardioCare system could be scaled through existing national platforms such as the NBPHSP and align with priorities outlined in Healthy China 2030. Its digital format supports integration into routine primary care and health checkup services, potentially strengthening chronic disease management at a population level.