Discussion
stroke, death, CKD, deaths
STROKE, EVENTS, ADVERSE EFFECTS, SECONDARY
Using an appropriately powered randomized controlled trial in people with CKD, we demonstrate that just 1 month of a simple low-cost intervention resulted in a significant reduction in urine sodium excretion, representing a significant reduction in dietary salt intake. The benefits of this 1-month intervention persisted at a lower level beyond the end of the 1-month intervention during the remaining year of this study.There is compelling evidence that reducing salt intake delivers health benefits at both individual and population levels.This likely reflects the difficulty that people with CKD face in trying to reduce their salt intake. Many different types of diet worldwide have become rich in salt, and unlike raw foods, commercially produced or processed foods typically have high levels of salt added to them and contribute substantially to salt intake.The use of potassium chloride as a salt substitute has been proposed as method of reducing salt intake. A recent study of cluster-randomized rural villages in China used a salt substitute (75% sodium chloride and 25% potassium chloride) or normal salt, and showed a reduction in stroke, major cardiovascular events, and death in people with a history of stroke or who were older than 60 years with high BP.Clinical trials designed to investigate the health benefits of lowering dietary salt intake have generally used relatively intensive, personalized, and expensive interventions to achieve the reductions necessary to reach statistical significance with relatively small numbers of participants over relatively short periods.To address this deficit, we tested a simple low-cost care bundle designed to help people with CKD to lower their salt intake. This intervention, the OxSalt care bundle, includes information and real-time reminders and is based on three key guiding principles to help empower people with CKD to lower their dietary salt intake. These three principles are focused on empowering people with CKD to: understand why reducing salt intake is beneficial, understand how to evaluate the salt content of food, and understand how to select or prepare food that is both appetizing and low in salt content. The intervention is based on low-cost digital technology, which can be delivered easily and cheaply at scale, and the provision of some simple printed material. We used routinely available services to host a website, send timed e-mails, and send timed text messages, and the costs for these services were relatively low and would increase very little with scale up of the intervention. The care bundle is a cheap and simple intervention that does not require any individual participant personalization and does not require specialist staff or training to deliver it, so it could easily be integrated into routine clinical practice.We did not seek to test adherence or engagement with the intervention, but rather to directly test the effects of providing the intervention as this is what could be done in routine clinical practice. The control group received standard routine care and so might have received or self-sourced general advice about salt intake. The purpose of the trial was to test the value of providing the intervention compared with not providing it.Our study raises the possibility that a longer intervention might result in even more reduction in salt intake. If the effect of the intervention diminishes over time, then there may be value in further, possibly brief, top-up “booster” interventions. Fluctuations in salt intake in the control group might seem to reflect routine care or curiosity about the nature of the intervention that those in the intervention group were receiving, but none of these changes were significant or sustained.This study was designed and powered to evaluate a change in dietary salt intake as measured using 24-hour urine sodium excretion. Although we measured BP and eGFR, this study was not designed or powered to detect significant changes in these parameters, but a small reduction in diastolic BP was seen with the intervention.We did not observe any adverse effects from lowering salt intake. Meta-analyses of large population datasets show a J-shaped relationship between salt intake and mortality.Any potential error arising from incomplete 24-hour urine collection should affect the intervention and the control arm equivalently. However, when analyzing the 24-hour urine collections for sodium content, we also measured creatinine content. The calculated sodium:creatinine ratio reduces any potential effect of collection error, and the results of this analysis confirmed the significant sustained reductions in salt intake in the intervention group.There is evidence of variability of sodium excretion over time within individuals.The magnitude of the reduction in dietary salt intake of 1.9 g is of real value and notable for an intervention of only 1 month duration. On the basis of estimates by the UK NICE, a smaller reduction in salt intake of 1.4 g/d that occurred between 2003 and 2011 prevented around 9000 cardiovascular deaths per year across the general UK population and saved the UK economy over £1.5 billion per year.Overall, this randomized controlled study demonstrates conclusively that a short, low-cost intervention, which can be delivered in primary or secondary care, helps people with CKD to lower their salt intake. Future studies are warranted to assess whether further benefit is derived from a longer intervention or later top-up interventions, with the cost reduced even further by large-scale use, which could include online self-enrollment.