Evaluation of a Simple Low-cost Intervention to Empower People with CKD to Reduce Their Dietary Salt Intake: OxCKD1, a Multicenter Randomized Controlled Trial

BACKGROUND
To evaluate the efficacy of a simple low-cost intervention to empower people with chronic kidney disease (CKD) to reduce their dietary salt intake.


METHODS
A randomized controlled trial in primary and secondary care comparing the OxSalt care bundle intervention versus standard care for 1 month. Participants were people with CKD and an eGFR (estimated glomerular filtration rate) greater than 20 ml/min/1.73m2 and were recruited from primary and secondary care. The primary outcome was a reduction in dietary salt intake, assessed by 24-hour urinary sodium excretion, after 1 month of the intervention.


RESULTS
201 participants were recruited. Dietary salt intake, as assessed from 24-hour urine sodium excretion, fell by 1.9 (±2.9) grams per day in the intervention group compared to 0.4 (±2.7) grams per day in the control group (p < 0.001). Salt intake was still reduced to a lesser extent over the following year in the intervention group.


CONCLUSIONS
A short, low-cost, easily-delivered intervention empowers people with CKD to reduce their dietary salt intake.Trial registrationClinicalTrials.gov NCT01552317.

1. Understand the health benefits of reducing salt intake 2. Understand how to evaluate the salt contents of food 3. Understand how to select or prepare food that is both appetizing and low in salt content The choice of one month as the duration of the care bundle intervention was pragmatic and based on considerations including consultation and input from patients during the development of the study. A longer intervention would have been more costly and our aim was to test a cheap and simple intervention. We hypothesised that if the intervention worked, then one month would be a long enough time period to allow participants to modify their food purchasing, preparation and consumption to favour foods that were lower in salt and to incorporate any altered behaviour into their regular routine.
Following randomization at the second baseline visit (see Figure 1), the intervention group were provided with a set of brief self-explanatory slides to look over during this visit at their own pace on an tablet or laptop computer; the slides presented key points about salt and provided some relevant examples. The theme of the slides was the three guiding principles above and the pace and timing of their review of the slides was determined by the participants. The purpose of the slides was: to introduce the health benefits of reducing salt intake, to introduce how to evaluate the salt content of food and to introduce approaches to selecting or preparing food that is both appetizing and low in salt content. The following written information was also provided to participants in the intervention group for them to take away in paper form: • A booklet recapitulating and expanding on the information in the introductory slides-that is, the benefits of reducing salt intake, how to evaluate the salt content of foods and how to select or prepare appetizing food that is low in salt content.
• A small double-sided credit card-sized reminder card about food labelling and salt content of food.
This was designed to be usable as a handy reminder when shopping and is reproduced below.
• A booklet containing information and guidance about the salt content of common foods grouped together to help guide decision-making for different meals (e.g. breakfast, lunch, etc.) or snacks.
• A double-sided single-page shopping guide summarizing the salt contents of key common foods and grouping them into high, medium and low salt categories to assist and simplify shopping decisionmaking. This is reproduced below.
• An information sheet with tips for eating-out to help decision-making around the salt content of foods ordered from a menu.
• An information sheet with simple suggestions for salt-free seasoning for home-cooking.
During the course of the 4-week intervention, participants received a series of automated pre-programmed emails and real-time text messages reminding them about different aspects of the information that they had already been provided with. The text messages and emails were sent out automatically by computer server.
Topics in these communications included, for example, motivational messages about the benefits of reducing salt intake, about making decisions about food purchasing and consumption that include consideration of salt content and tips for healthy food choices.
Throughout the 4-week intervention, participants had access to a website containing online versions of the information and guidance that had been provided in the written paper material. The information on the website was the same as the information provided in printed form.

Savoury Snacks
Salt 'n' Shake crisps (without the salt sachet), unsalted nuts, plain popcorn   Finished school at 16 with one or more qualifications 11 15 Vocational training or apprenticeship 19 13 Finished school age 18 with one or more higher qualifications taken 9 8 Finished university or other higher education with a degree or diploma 23 33 The control and intervention groups do not differ significantly (chi-square, p = 0.33) Supplementary Table 2 Supplementary  Time periods are from the start of the 1-month intervention.
Supplementary Table 4 Supplementary The mean baseline represents the mean of the first and second baseline measurements.