The goal of ASC is to reduce salt intake by 15% by 2021 in the six target provinces in China. The specific objectives are to reduce salt intake by at least 1 g/day (about 17 mmol/day) at home, and to reduce salt use by at least 0.5 g (about 8.5 mmol) per 100 g in restaurant dishes. To reach these goals, several programs targeting the major sources of salt intake in China have been developed and are being implemented.

To achieve these goals and objectives, the ASC project developed six programs targeting the low health literacy related to salt reduction and the three sources of salt intake in China: home cooking, restaurant foods, and prepackaged foods. Program 1 is a salt reduction education campaign, which will form the basis of all the other programs. Program 2, app-based intervention study (AIS), is a primary school-based program delivering salt reduction activities for the homes of school children, based on the assumption that parents and grandparents are more likely to change their habit of high salt intake for the sake of the health of their children and grandchildren [18,19]. Program 3, home cook-based intervention study (HIS), will establish a community-level training and support system to help family cooks reduce salt use in home cooking. Program 4, restaurant-based intervention study (RIS), aims to create an environment in restaurants that is conducive to consumers opting for reduced-salt dishes, and to train cooks to use less salt while cooking. Program 5, comprehensive intervention study (CIS), simulates the real-world implementation of all of the intervention packages or components developed in Programs 1-4 with the purpose of identifying barriers and facilitators when scaling up. Program 6 is a two-fold campaign with the aims of educating and supporting consumers choosing less salted prepackaged foods (Program 6.1), and convincing food manufacturers to reformulate their food products by gradually reducing the amount of salt added (Program 6.2).

The governance and management structure of the ASC unit and programs are illustrated in Figure 1. The governing council consists of 10 members, 5 of whom are the top leaders from the 5 member organizations of the ASC unit. The other 5 members are academics from independent organizations, including the National Preventive Medicine Association (2 members with Chairman), China Nutrition Society, Chinese Hypertension League, and Peking University Health Science Center. The governing council provides guidance by (1) reviewing ASC’s goals and strategies, (2) setting the tone for cooperation and communication, and (3) evaluating ASC’s overall performance and achievement every year. The technical committee is composed of the leading principal investigators of all programs and independent experts in salt reduction. The committee members will work together to finalize documents (eg, research protocols and education materials), provide support in program implementation, and act as the ultimate decision maker in handling any practical issues. Supervised and supported by the governing council and technical committee, the ASC office, located in TGI China, will be responsible for coordinating all of the partners to implement the proposed programs, and to ensure the smooth running of the whole unit and its programs to achieve quality outputs in a timely manner.

A two-stage strategy is adopted to ensure that the proposed salt reduction programs are well prepared, evaluated, and tailored. At stage 1 (first 2 years), the intervention packages in each program will be developed and evaluated, before being scaled-up and integrated as policies at stage 2.

At stage 1, the different intervention packages of Programs 2-5 will be evaluated with open-label cluster RCTs in various settings. The four RCTs will be conducted collaboratively under the same governance and time frame. Evaluation will be performed using standardized questionnaires, physical examinations, laboratory tests, and data collection systems that are as identical as possible so that the data collected across the RCTs can be pooled together for overall salt intake estimation and overall effectiveness evaluation.

The key features of the six programs of ASC at stage 1, including the theories and key intervention components of the four RCTs (Programs 2-5 at stage 1), are summarized in Table 1. Separate protocols for each of the four RCTs describing the study setting and participants, randomization, intervention, sample size calculation, outcomes, and data collection and analysis will be published before the end of stage 1. These results (especially those related to effectiveness and process evaluation) will also be published separately after the RCTs are completed.

The study participants are grade 3 primary school students (8-9 years old) and their parents/grandparents (1 student and 2 adults for each family) in AIS, home cooks and their family members (1 home cook and one other adult member for each family) in HIS, and adults (1 adult from each participating family) in CIS. Although the participant recruitment may vary among AIS, HIS, and CIS, in all cases, these will be local residents with no plan to move out of the city or village within 24 months, and agree to participate in the studies. The exclusion criteria are (1) pregnant women and those actively lactating; (2) individuals who are currently participating in any other clinical trials; (3) those with severe psychiatric or physical diseases that might impact intervention and follow-up; (4) individuals who are unable or not suitable to collect 24-hour urine due to the following conditions: aconuresis; acute/chronic urinary tract infection, vaginal infection and perianal infection; acute hemorrhagic diseases in the urinary tract, vagina, and digestive tract; and severe vomiting and diarrheic symptoms. In RIS, the study subjects are restaurants with dish salt content as the primary outcome, which will be evaluated using the average sodium content of the 5 best-selling dishes.

At the end of stage 1, the education materials and the effective intervention packages or components will be combined as a scale-up intervention package on salt reduction (SIPS) for broad use at stage 2. A final evaluation to assess the impact of the scaling-up and the lasting effectiveness of the intervention packages will be carried out at the end of 1 year of scale-up. The SIPS will subsequently be further promoted over a larger scale across China using existing platforms and resources such as China’s Healthy Lifestyle for All Initiative of the China CDC and the Chinese Center for Health Education.

To avoid contamination in control groups, all RCTs are being conducted in different counties or districts of the six provinces: Heilongjiang, Hebei, Hunan, Jiangxi, Sichuan, and Qinghai, which cover the north, south, central, east, and west part of China (Figure 2). HIS, RIS, and CIS are carried out in the above six provinces, whereas AIS is conducted in only three provinces: Hebei (north), Sichuan (central), and Hunan (south).

To facilitate implementation, ASCloud, a cloud-based information system, has been designed and developed by Beihang University to support health education and promotion to the public, restaurants, and food industry; intervention delivery; and project and data management for all programs. This is based on our experience in delivering research projects [24], and on systematic reviews related to nutrition improvement [25] and salt reduction [26] using mHealth technology. The structure of ASCloud is illustrated in Multimedia Appendix 1.

The evaluation method of the effectiveness or impact of the proposed interventions has been specifically designed for each program. In all RCTs, the 1-year effectiveness of the intervention will be assessed by comparing the salt reduction achieved between the intervention and control arms from baseline to the end of stage 1, and the sustained effectiveness over the following year will be assessed by comparing the salt reduction achieved between the intervention and control arms of AIS, HIS, and CIS from baseline to the end of stage 2. Figure 3 shows the design, sample size, and evaluation of primary outcomes for RCTs in Programs 2-5.

The sample sizes indicated in Figure 3 are equal to or slightly larger than the calculated numbers for the RCTs based on target populations (children and adults in AIS, home cooks and family members in HIS, community adults in CIS, and restaurants in RIS), primary outcomes (24-hour sodium excretion in AIS, HIS, and CIS; average sodium content of the 5 best-selling dishes for a restaurant in RIS), standard deviations of primary outcomes (85 mmol/day for 24-hour sodium excretion [19], and 1 g salt/100 g dish [27]), expected minimum salt reduction (25 mmol/day in AIS and CIS; 20 mmol/day for HIS; 0.5 g/100 g dish for RIS [27]), intraclass correlation coefficient (0.05 for AIS, HIS, and CIS [19], and no cluster effect for RIS), drop-out rate (<20%) for individuals/clusters, type I error (5%), and power (>80%), as well as reasonable cluster size (11 students and families in each school in AIS, 13 families in each village in HIS, and 30 adults in each village in CIS).

Secondary outcomes will consist of process evaluation, changes in KAP on salt intake, and economic evaluation. Overall KAP on salt, and overall salt intake levels will also be estimated by pooling the data collected in AIS, HIS, and CIS at baseline, at the end of stage 1, and at the end of stage 2.

Statisticians will be blinded to the intervention assignments during data analysis. An intention-to-treat approach will be adopted for analysis of the primary outcomes. The effect of the intervention on the outcomes will be tested using linear mixed models. For AIS, HIS, and CIS, participants will be nested within family units and families nested within clusters (schools, villages, or towns). Group (intervention, control), time (baseline, end of trial), and time-by-group interaction will be included in the model, with the interaction effect indicating differential change according to group from baseline to the end of the trial. We will adjust for the stratification and potential confounding variables at randomization.

Our study will have three major data outputs: (1) data obtained from the evaluation of each RCT’s effectiveness (Table 2); (2) data obtained from the process monitoring and evaluation, which will consist of quantitative data automatically generated by the smartphone apps used as intervention tools in the RCTs, as well as qualitative data collected for process evaluation; and (3) monitoring and evaluation data on the coverage and usage of the salt reduction materials and tools, which will be recorded by ASCloud during the scaling-up phase. With the exception of the routine work log and qualitative data collected for process evaluation, most of the data will be collected using specially designed electronic systems, including a mobile device-based electronic data capture system (mEDC) and the ASCloud server, which can capture activities such as log in/log out and access to certain features through different kinds of front ends, Web portals, and mobile apps. The mEDC has an improved process and quality control feature compared with a traditional EDC, and has been validated and widely used in other clinical trials [24,28].

All cleaned and locked datasets for each RCT, together with the study design, questionnaires, code lists, and definitions of databases and variables, will be stored in TGI China, with a unique ID number attached but no personal identifiers, following an established standard operating procedure for data security. To guarantee data security, the mobile app developer (ie, the Information Technology team at Beihang University) will follow the “Mobile Application Information Service Regulation” issued by the Cyberspace Administration of China in 2016 [30]. Although personal data will be accessible to the app developer, disclosure of such information is prohibited.

During development of the overall design of ASC and the specific protocols for each RCT, people from the target populations and those involved in the implementation of the interventions were consulted at least once through meetings, teleconference, and site visits. The consulted individuals included primary school teachers, parents of primary school children, family cooks, consumers of prepackaged food, food producers, restaurant staff, community residents, and policy makers. All ideas on new interventions, opinions on the feasibility of specific interventions, and suggestions to improve their design and implementation were carefully considered. All participants will be informed of the study progress by regular communication via the ASC newsletter, WeChat, and website. Upon completion of the study, we will disseminate the results to all participants and discuss the translation of our study findings to practice.

ASC is a research unit led by a strong multidisciplinary team with members from international and national institutes engaging in nearly all relevant areas on salt reduction in China. The ASC program is comprehensive, including a salt awareness campaign, legislation support, and RCTs evaluating the strategies dealing with key challenges on salt reduction in China. ASC uses innovative digital health technologies to support the delivery of interventions as well as project and data management. The real-time monitoring and process evaluation can help to increase the fidelity of complex interventions.

As a unit, the six programs of ASC will provide a set of novel approaches to reduce salt intake in China. The expected outputs of ASC include: (1) several evidence-based intervention packages addressing major sources of salt intake; (2) evidence-based salt reduction strategies and experience on policy advocacy along with scaling-up in different regions and populations; and (3) study reports and publications to highlight the gaps, needs, barriers and facilitators, and strategies in salt reduction among different populations. All these major outputs will make significant contributions to the national policies, programs, and initiatives on the prevention and control of noncommunicable diseases as well as the promotion of healthy diets and healthy lifestyle in China. Owing to the strong policy support, multidisciplinary research team, and close partnership with all key national agencies, ASC is most likely to succeed in achieving its intended objectives.

To date, ASC has already made significant progress in achieving its academic impact. As shown in Textbox 1, ASC has attracted the attention of key departments of the Chinese central government. With the support of relevant government agencies, the development of detailed scaling-up plans is underway. If the program is implemented and sustained across China, it will reduce population salt intake and thereby prevent hundreds of thousands of strokes, heart attacks, and heart failure each year, leading to major cost-savings to individuals, their families, and the health service. Although our study will be carried out in China, the outcomes could potentially be adopted by many other countries. Additionally, our model on salt reduction could possibly be adapted for other dietary and lifestyle changes to prevent CVD and other noncommunicable diseases, which will have major public health implications.

The findings of this study will be disseminated widely through conference presentations, peer-reviewed publications, press releases, and social media. In China, the results and effective interventions will be disseminated nationwide through the existing system of health education, disease control, and prevention. Furthermore, the results will be disseminated worldwide through World Action on Salt and Health [34], which is a global nonprofit organization of 600 members from 100 countries with the mission to improve the health of populations by reducing salt intake.

The interventions for each program of ASC are complex. Low compliance to the intervention may lead to negative results for the primary outcomes. In addition, the implementation of collecting 24-hour urine is very demanding. Fidelity to interventions and quality control for effectiveness evaluation are both critical to the success of the programs. With the widespread implementation of Healthy China 2030 initiatives, salt reduction is being promoted by many other programs. Therefore, it might be very difficult to distinguish the contributions of ASC from those of other programs.

The ASC project is progressing smoothly. The intervention packages and components evaluated at stage 1 will provide strong support for salt reduction in China, and could potentially be adopted by many other countries worldwide.