App based education programme to reduce salt intake (AppSalt) in schoolchildren and their families in China: parallel, cluster randomised controlled trial

Abstract Objective To determine whether a smartphone application based education programme can lower salt intake in schoolchildren and their families. Design Parallel, cluster randomised controlled trial, with schools randomly assigned to either intervention or control group (1:1). Setting 54 primary schools from three provinces in northern, central, and southern China, from 15 September 2018 to 27 December 2019. Participants 592 children (308 (52.0%) boys; mean age 8.58 (standard deviation 0.41) years) in grade 3 of primary school (about 11 children per school) and 1184 adult family members (551 (46.5%) men; mean age 45.80 (12.87) years). Intervention Children in the intervention group were taught, with support of the app, about salt reduction and assigned homework to encourage their families to participate in activities to reduce salt consumption. Main outcome measures Primary outcome was the difference in salt intake change (measured by 24 hour urinary sodium excretion) at 12 month follow-up, between the intervention and control groups. Results After baseline assessment, 297 children and 594 adult family members (from 27 schools) were allocated to the intervention group, and 295 children and 590 adult family members (from 27 schools) were allocated to the control group. During the trial, 27 (4.6%) children and 112 (9.5%) adults were lost to follow-up, owing to children having moved to another school or adults unable to attend follow-up assessments. The remaining 287 children and 546 adults (from 27 schools) in the intervention group and 278 children and 526 adults (from 27 schools) in the control group completed the 12 month follow-up assessment. Mean salt intake at baseline was 5.5 g/day (standard deviation 1.9) in children and 10.0 g/day (3.5) in adults in the intervention group, and 5.6 g/day (2.1) in children and 10.0 g/day (3.6) in adults in the control group. During the study, salt intake of the children increased in both intervention and control groups but to a lesser extent in the intervention group (mean effect of intervention after adjusting for confounding factors −0.25 g/day, 95% confidence interval −0.61 to 0.12, P=0.18). In adults, salt intake decreased in both intervention and control groups but to a greater extent in the intervention group (mean effect −0.82 g/day, −1.24 to −0.40, P<0.001). The mean effect on systolic blood pressure was −0.76 mm Hg (−2.37 to 0.86, P=0.36) in children and −1.64 mm Hg (−3.01 to −0.27, P=0.02) in adults. Conclusions The app based education programme delivered through primary school, using a child-to-parent approach, was effective in lowering salt intake and systolic blood pressure in adults, but the effects were not significant in children. Although this novel approach could potentially be scaled up to larger populations, the programme needs further strengthening to reduce salt intake across the whole population, including schoolchildren. Trial registration Chinese Clinical Trial Registry ChiCTR1800017553.

. Schedule of the intervention activities. Figure S3. Changes in the average salt intake during the 12 month intervention period for children and adults in the intervention group (values were generated by the app using the seven day salt estimation method). Table S2. Sensitivity analysis for salt intake (g/day) as calculated from 24 hour urinary sodium excretion. Table S3. Salt intake (g/day) as measured by 24 hour urinary sodium excretion by subgroup. 1

Supplement 1: Description of the app based salt reduction intervention activities
The app based salt reduction education (AppSalt) is an m-Health intervention programme. A smartphone app named "AppSalt" was designed to provide a platform for delivering standardised education courses and tasks to grade 3 primary schoolchildren (8-9 years old) and their parents and grandparents. The app was installed in parents' or grandparents' smartphones and only adults were authorised to operate it. Children's tasks were to ensure that their parents or grandparents complete the lessons together with them and get the whole family involved in salt reduction activities. Besides the app, we implemented various offline activities. In total, there were five intervention components in the AppSalt programme, aiming to mobilise children to get their whole family to reduce salt intake. The details of the five intervention strategies of the AppSalt programme are described below.

Online education courses delivered through smartphone app
Over the 12 month intervention period, there was a total of 9 salt reduction education lessons (Table S1) and 12 usual health education lessons as normally included in the curriculum that did not contain salt-related material, e.g. flu prevention. All lessons were delivered through the app. A detailed description of the app including its features and functions has been published previously. 1 Figures S1 and S2 are two examples of the app (NB: The app is in Chinese and a few key words were translated into English and added to the screenshots).
Each lesson consisted of a 10-min video and a quiz to re-enforce important messages. Most of these lessons had a practical session to help participants put what they have learned into practice. The salt reduction education lessons covered knowledge and techniques for reducing salt intake, including the harmful effects of salt on health, the recommended level of salt intake, skills in reducing salt used in cooking and information on the sodium-reduced and potassium-enriched salt substitutes. Children and their family members could decide when and where to learn the lessons at their convenience.

Estimating and monitoring salt intake
The estimation and monitoring of salt intake was a task for the participants to complete and the data were recorded in the app. This task consisted of a seven day diary on salt intake for the family, which included weighing salt and other condiments (e.g. soy sauce) used in home cooking, estimating the consumption of processed food high in salt, and recording the frequency of eating out during the seven days. After completing this diary, the app calculated the average salt consumption using an embedded algorithm and generated a salt reduction action plan for each family member according to their salt intake and major sources of salt in their diet. All families were asked to complete this procedure at baseline and every three to four months thereafter. The information obtained could help each family member set a lower salt intake target and salt reduction targets for the top 3 contributors, e.g. reducing salt used in cooking by 50%. At the same time, the data shown on the app could help individuals monitor their progress on achieving lower salt intake.

Competitions and awards
A total of four competitions were organized by the schoolteachers (Table S1), including one art competition, two knowledge competitions, and one writing competition. After each competition, the top 30 children at each study site were awarded certificates and prizes.

Parent meetings
During the 12 month intervention period, schoolteachers were required to organise three to four face-to-face seminars for both children and adults to encourage peer communications and to collect their feedbacks on the programme. These seminars coincided with the schools' parent meetings, usually taken place at the beginning and the end of each school term. The topics of the seminars were related to the salt reduction courses or activities around that time.

Supportive environment
Posters were provided to the schools to help create a supportive environment for salt reduction on campus. The themes of these posters corresponded to the topics of the salt reduction education videos delivered through the app. Besides, some practical tools for reducing salt intake were provided to families, including salt-restriction spoons and salt awareness stickers.  Figure S3. Changes in the average salt intake during the 12 month intervention period for children and adults in the intervention group (values were generated by the app using the seven day salt estimation method).   SD=standard deviation. *Comparison of the means between baseline and 12 month follow-up. Positive values=increases from baseline to 12 month follow-up; negative values=reductions from baseline to 12 month follow-up. †Comparison between intervention and control groups in the changes from baseline to 12 month follow-up. Positive values=the intervention group had a greater increase or less decrease from baseline to 12 month follow-up than the control group; negative values=the intervention group has a greater decrease or smaller increase from baseline to 12 month follow-up than the control group. ‡Adjusted for age, sex, body mass index (body weight in children instead), outdoor temperature, study site, highest education level in the family.  SD=standard deviation. *Comparison of the means between baseline and 12 month follow-up. Positive values=increases from baseline to 12 month follow-up; negative values=reductions from baseline to 12 month follow-up. †Comparison between intervention and control groups in the changes from baseline to 12 month follow-up. Positive values=the intervention group had a greater increase or less decrease from baseline to 12 month follow-up than the control group; negative values=the intervention group has a greater decrease or smaller increase from baseline to 12 month follow-up than the control group.
‡Adjusted for age, sex, body mass index (body weight in children instead), outdoor temperature, study site, highest education level in the family. § Defined as systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg or self-reported hypertension.