Sodium Watchers Program - Hypertension (SWAPHTN)

Hypertension or high blood pressure is known as a silent killer because it can exist for decades without producing symptoms while leading to chronic cardiovascular disease and stroke. The long-term objective of this program of research is to improve blood pressure control and prevent cardiovascular disease development in adults with hypertension by increasing adherence to a sodium-restricted diet (SRD). The Sodium Watchers Program is an innovative self-management intervention using a gradual sodium adaptation strategy that allows individuals to monitor, and over time, reduce sodium content in their food, thereby increasing the ability to maintain an SRD long term. The purpose of the proposed randomized, controlled trial is to test the effects of the Sodium Watchers Program-Hypertension(SWaP-Hypertension), designed to improve blood pressure control of hypertensive adults using a gradual sodium reduction adaptation strategy.

The SWaP-Hypertension intervention consists of 14 weeks of education [4 weekly education sessions (45 minutes) followed by 5 bi-weekly sessions 5-20 minutes] that will be held at participants' preferred time delivered to their homes using a video conferencing program through a mini iPad. Using a 2-group design [SWaP-Hypertension (n=20) versus Usual care (n=10)], randomized, controlled trial with 30 hypertensive adults, the effects of the SWaP-Hypertension program on adherence to SRD, systolic and diastolic blood pressure, salt taste preference, and dietary patterns will be determined at 4 months. Data will be analyzed using repeated measures analysis of variance.

Specific Aim 1: To compare sodium intake (as reflected by 24-hour urinary sodium excretion), systolic and diastolic blood pressure, salt taste preference, and dietary patterns in the SWaP-Hypertension intervention group with the usual care group at 4 months.

Hypothesis 1: The intervention group will have a greater decline in 24-hour urinary sodium excretion and systolic and diastolic blood pressure, lower salt taste preference, and shift dietary patterns toward lower sodium foods than the usual care group at 4 months.

High blood pressure (systolic blood pressure ≥140 mmHg or diastolic blood pressure≥ 90 mm Hg), is a leading risk factor for cardiovascular disease and stroke.1 More than 80 million adult Americans have high blood pressure and it is projected that 41.4% of US adults will have hypertension by 2030.

Sodium restriction is believed to decrease blood pressure. According to a recent meta-analysis of 24 randomized controlled trials, dietary interventions (e.g., low sodium diet, low sodium/high potassium, low sodium/low calorie, Mediterranean diet, and DASH diet) were effective in reducing systolic blood pressure by an average of 3.07 mmHg and diastolic blood pressure by an average of 1.81 mmHg. These changes are minimal and are often not sustained due to the difficulty of following such diets.

Most interventions for improving adherence to SRD have focused on increasing specific skills, including how to read food labels, choose low sodium foods when eating out, and engage family support. However, these interventions do not effectively address critical barriers to SRD adherence, which include preference of high salt food and habitual dietary patterns. Salt taste reception involves the sodium ion movement through sodium channels at the apical end of the taste bud. High salt foods become preferable when individuals' taste buds adapt to foods high in sodium. Preference for salty foods results in high levels of dietary sodium intake.

These barriers are particularly salient for older patients as taste bud density decreases with age resulting in an increasing preference for salt and consumption of foods high in sodium. Combined, low palatability of low sodium foods and preference for high sodium foods make dietary changes difficult. Since at least 8-10 weeks of exposure to an SRD is required to alter sodium palatability (i.e., alter salt acuity and salt taste preference) abrupt and marked reductions in sodium intake are rarely sustained and can have the unintended consequence of exacerbating sodium-seeking behaviors. New approaches are needed to improve long-term adherence to SRD.

An innovative dietary self-care intervention has been developed to overcome sensory barriers to adherence. Abrupt and marked reductions in sodium intake can lead to sodium-seeking behaviors, and thus, changing dietary preferences requires at least 8 weeks to reach a new hedonic state and to reset sodium taste buds. Thus, an intervention that uses a gradual adaptation strategy should produce the best long-term adherence results. Most educational interventions have focused on improving knowledge by teaching patients specific skills including how to read food labels, how to choose low sodium foods when eating out, and how to modify their usual diet.

Design: A two-group, randomized, controlled design will be used to determine the effect of the SWaP-Hypertension on outcomes of hypertensive adults. A total of 30 eligible participants will be randomly assigned to intervention (n=20) or usual care group (n=10). We will assign 20 participants in the intervention that is two times more than the usual care group in order to maximize limited funding sources. The intervention will be delivered for 14 weeks using video conferencing on an iPad device. Post-intervention will be measured at 4 months follow up to examine short-term effect. Dependent variables included adherence to the SRD, systolic and diastolic blood pressure, salt taste preference, and dietary patterns.

Intervention: Sodium Watchers Program-Hypertension (SWaP-Hypertension): The SWaP- is an educational-behavioral intervention that uses an electronic salt monitoring device to promote both rural adults with high blood pressure and their family partner's ability to self-monitor sodium intake and gradually decrease their appetite for salt. The program consists of 14 weeks education [4 weekly education sessions (45 minutes) followed by 5 bi-weekly sessions (15-20 minutes)] that will be held at the dyads' preferred time delivered to their homes using a video conferencing program through a mini iPad. Video conferencing technology is used to enhance the feasibility and decrease the burden of participating in the intervention. Bi-weekly booster sessions are added to provide on-going support to maintain acquired self-care behaviors and individual goals for reductions in dietary sodium. The booster sessions include positive reinforcement of success and identification of strategies to overcome ongoing or new challenges. A nurse interventionist who experienced in delivering the intervention will assist individual goal settings and reinforces strategies in each session.

Usual care group: The usual care group receive their routine medical and nursing care for hypertension that consists of a recommendation to follow an SRD and take medications as ordered.

Measures: Table 2 lists dependent variables and their measurement in the study. To completely characterize subjects and monitor potential intervening variables, data about the individuals' age, sex, race/ethnicity, education level, comorbidities, medications, and cognitive impairment will be collected from the participant interviews or using a structured questionnaire. Comorbidity will be measured using the Charlson Comorbidity Index. Data about medications will be self-report. Cognitive impairment will be assessed using the Mini-Cog. This 3-minute screening instrument consists of drawing a clock and three-word recall. It is sensitive, reliable and valid in individuals with low literacy and low socioeconomic status. Our research staff has extensive experience in all data collection proposed in this study.

Procedure: Permission to conduct the study was obtained from the University of Kentucky, Institutional Review Board. Hypertensive adults are referred to this project by physicians and nurse practitioners from the outpatient cardiology and internal medicine services at the University of Kentucky HealthCare at Lexington. After referral, a trained research nurse will screen patients for eligibility by medical chart review. For eligible participants, the study requirements are explained and signed informed consents are obtained. After we obtain the informed consents from eligible participants, urine containers and collection devices (urinals for men and toilet "hats" for women) are provided before home visits. The participants are instructed how to collect the 24-hour urine specimen, and written standard instructions are also provided. Urine is kept in the container and does not need refrigeration. Research staff and participants set up the starting day of urine collection and pick up urine specimens in their home. During the home visit, they are assisted to complete all study questionnaires using the REDCap system and assessment of blood pressure and salt taste preference. A trained staff member will deliver education materials and an iPad to the participants in the intervention group and instruct them how to use the video conference program (i.e., Zoom Mobile app) on iPad by testing trial of a video-conferencing program. A toll-free phone number is to call at any time for assistance using the iPad is provided. The usual care group will receive a mini iPad with instruction of using emails and text message to contact research staff. All participants will follow the same data collection procedure as during the baseline assessment for 4-months follow-up time point.