A Mobile Health Salt Reduction Intervention for People With Hypertension: Results of a Feasibility Randomized Controlled Trial

Abstract

Background A high-salt diet is a risk factor for hypertension and cardiovascular disease; therefore, reducing dietary salt intake is a key part of prevention strategies. There are few effective salt reduction interventions suitable for delivery in the primary care setting, where the majority of the management and diagnosis of hypertension occurs. Objective The aim of this study is to assess the feasibility of a complex behavioral intervention to lower salt intake in people with elevated blood pressure and test the trial procedures for a randomized controlled trial to investigate the intervention’s effectiveness. Methods This feasibility study was an unblinded, randomized controlled trial of a mobile health intervention for salt reduction versus an advice leaflet (control). The intervention was developed using the Behavior Change Wheel and comprised individualized, brief advice from a health care professional with the use of the SaltSwap app. Participants with an elevated blood pressure recorded in the clinic were recruited through primary care practices in the United Kingdom. Primary outcomes assessed the feasibility of progression to a larger trial, including follow-up attendance, fidelity of intervention delivery, and app use. Secondary outcomes were objectively assessed using changes in salt intake (measured via 24-hour urine collection), salt content of purchased foods, and blood pressure. Qualitative outcomes were assessed using the think-aloud method, and the process outcomes were evaluated. Results A total of 47 participants were randomized. All progression criteria were met: follow-up attendance (45/47, 96%), intervention fidelity (25/31, 81%), and app use (27/31, 87%). There was no evidence that the intervention significantly reduced the salt content of purchased foods, salt intake, or blood pressure; however, this feasibility study was not powered to detect changes in secondary outcomes. Process and qualitative outcomes demonstrated that the trial design was feasible and the intervention was acceptable to both individuals and practitioners and positively influenced salt intake behaviors. Conclusions The intervention was acceptable and feasible to deliver within primary care; the trial procedures were practicable, and there was sufficient signal of potential efficacy to change salt intake. With some improvements to the intervention app, a larger trial to assess intervention effectiveness for reducing salt intake and blood pressure is warranted. Trial Registration International Standard Randomized Controlled Trial Number (ISRCTN): 20910962; https://www.isrctn.com/ISRCTN20910962

Effect of salt reduction interventions in lowering blood pressure: A comprehensive systematic review and meta-analysis of controlled clinical trials

“…Of the 50 trials, 25 assessed the effects of the interventions among hypertensive participants [ 23 , 24 , 26 , 29 – 31 , 39 , 42 – 50 , 52 – 54 , 58 ], three among normotensive individuals [ 30 , 34 , 35 ], and 22 among both hypertensive and normotensive participants [ 21 , 22 , 25 , 27 , 28 , 31 , 33 , 36 – 38 , 40 , 41 , 51 , 55 – 57 , 59 , 60 ]. In 29 studies, BP was measured with an automatic sphygmomanometer, in five with a manual mercury sphygmomanometer [ 31 , 40 , 42 , 49 , 53 ], and six studies did not report BP measurement method [ 22 , 30 , 48 , 51 , 59 , 60 ]. Furthermore, in all the studies, BP measurement was performed by health professionals or trained personnel, with the exception of three studies that relied solely upon self-reported measures [ 34 , 35 , 47 ].…”

“…Furthermore, in all the studies, BP measurement was performed by health professionals or trained personnel, with the exception of three studies that relied solely upon self-reported measures [ 34 , 35 , 47 ]. The included studies employed different types of intervention strategies that were categorized into four domains; 21 trials with nutritional education [ 21 , 28 , 31 , 38 , 40 – 42 , 46 , 49 , 50 , 52 , 55 , 56 , 59 – 61 ], 17 used salt substitutes [ 23 , 25 – 27 , 29 – 31 , 33 , 43 – 45 , 54 , 58 ], ten used self-help materials [ 34 – 37 , 39 , 47 , 48 , 51 , 53 , 57 ], and two trials employed food reformulation [ 22 , 24 ]. The control groups of all trials received usual care or no intervention.…”

“…All RCTs described the randomization, of which 4 studies had an inappropriate random allocation method [ 39 , 40 , 50 , 54 ], and 17 studies did not provide precise information of randomization [ 24 , 26 , 34 , 35 , 38 , 41 , 44 , 45 , 55 , 56 , 58 – 60 ]. While 15 studies used allocation concealment to prevent selection bias [ 23 , 27 – 30 , 37 , 43 , 45 , 46 , 48 , 51 – 53 , 57 , 61 ], eight studies did not mention it [ 38 – 41 , 49 , 50 , 54 , 55 ]; the other remaining studies did not clearly explain any procedure used to conceal the allocation. Most studies did not report adequate information to judge the participants, personnel, and outcome assessors’ blinding.…”

“…Furthermore, in several trials, participants and personnel’s blinding was not completely applicable due to the nature of the intervention strategies, such as education and self-help materials. In addition, 29 articles that described dropouts and their causes and also group differences in terms of dropout were considered as low risk of bias [ 21 – 26 , 28 – 30 , 36 – 40 , 42 – 45 , 47 , 48 , 50 – 54 , 56 , 57 , 60 , 61 ]. Moreover, 11 studies had incomplete outcome data [ 27 , 31 , 33 – 35 , 41 , 46 , 49 , 55 , 58 , 59 ].…”

A Mobile Phone App Intervention to Promote Healthy Salt Intake Among Adults: Protocol for a Randomized Controlled Study

“…To our knowledge, there is only one study available in the literature that evaluated the effect of an app intervention to reduce salt consumption using BCW; however, the study was focused on people with arterial hypertension and not on the general population [ 49 ].…”