A Geofencing-Based Adaptive Messaging System to Support Patient Self-Management of a Low-Sodium Diet in Hypertension

High dietary sodium intake is linked to hypertension, stroke, heart failure, and kidney disease. Current recommendations are a sodium intake of less than 2,300 milligrams (mg) a day for those under 51 and less than 1,500 mg a day for older adults; African Americans; and those with hypertension, diabetes, and chronic kidney disease. However, the average intake for Americans is 3,400 mg per day, with the consumption of pre-processed and restaurant foods contributing to 75 percent of sodium intake in the average US diet. Most patients prescribed a low-sodium diet are unaware of the sodium content of the foods they eat and could benefit from assistance at groceries stores and restaurants to follow the recommendations.

This research developed and evaluated mobile application (app) adaptive messages that assisted individuals with hypertension to adhere to a low-sodium diet. Geofencing technology was used to identify patient location so that upon entering a grocery store, the individual was reminded to scan the barcode on food items. The app used red, yellow, or green traffic light signals to indicate high, medium, or low salt content. When walking into a restaurant, the mobile app notified users of three low-sodium meal options available at that specific restaurant. A daily query to participants asked about their reduction of high-sodium foods and provided examples of alternatives, tracking how well they had done in reducing target foods.

The specific aims of the research were as follows:

• Establish a geofencing-based, adaptive notification message system for the mobile app using participant feedback to facilitate reducing dietary sodium intake. 
• Determine the effectiveness of the newly developed mobile app that provides geofencing-based push messages on dietary sodium intake and confidence following a low-sodium diet. 

The research took place in two phases. Phase one was the implementation of the mobile app from an existing prototype. In this phase, three focus groups were held to inform development of the messages. Twenty-seven messages were created and personalized based on location and an individual’s confidence in being able to follow a low-sodium diet. In the second phase, enrolled individuals were randomized to either the mobile app or usual care. Participants were followed with dietary assessments, self-care measurements, and clinical measurements, including laboratory assessment of kidney function.

From baseline to 8 weeks, the users of the app had significantly greater reductions in sodium intake by both subjective and objective measures. Systolic blood pressure showed a non-statistically significant improvement. At the end of the study, more than 70 percent of participants agreed the app was useful and that information received from the app was important. Most felt it was easy to use and that others could learn to use it quickly. Participant’s confidence in being able to follow a low-sodium diet did not improve. The researchers concluded that a larger clinical trial is needed to further investigate the impact of the app on blood pressure and that research should be done to determine how providers could prescribe this type of intervention to patients.