SalT supplementation in Older adults with Orthostatic intolerance Disorders (STOOD) trial: a study protocol for a feasibility randomised controlled trial

Orthostatic hypotension (OH) is a common cause of falls, and key source of morbidity and mortality due to injury (e.g. hip fracture). Current guidelines recommend increasing salt intake in patients with symptomatic orthostatic hypotension. However, the evidence underpinning this recommendation is poor, based primarily on small trials with very short-term follow-up (<8 weeks). High salt intake might improve quality of life and reduce the risk of falls, but might also increase the long-term risk of cardiovascular disease, in patients with OH. STOOD is a two-group, parallel, open-label, randomised controlled, single centre trial. Adults aged ≥65 years with symptomatic orthostatic hypotension, and estimated moderate salt intake (based on screening questions) will be eligible. Exclusion criteria include uncontrolled hypertension (>180/110 mmHg), heart failure (NYHA class III/IV, or ejection fraction < 30%), loop diuretic use, chronic kidney disease (eGFR < 30 ml/min/1.73m 2 ), hyponatraemia (serum sodium < 125 mmol), evidence based clinician recommendation of high or low salt diet, and inability to provide informed consent. Participants will be randomised to receive salt supplementation of 5 g encapsulated sodium chloride per day (in addition to usual care) or usual care alone. The primary feasibility outcome will be recruitment and retention of the target sample size of 48 participants. The primary efficacy outcome is change in orthostatic hypotension questionnaire score from baseline to 6-month follow-up. A recommendation for long-term higher salt intake may have adverse cardiovascular consequences, which necessitates robust evidence of efficacy and identification of the optimal range of salt intake associated with the greatest reduction in falls risk and lowest cardiovascular risk. Our study will establish the feasibility and acceptability of evaluating the intervention (salt supplementation) in a single centre, and provide preliminary evidence of treatment effect of salt supplementation for management of orthostatic hypotension. ClinicalTrials.gov Identifier: NCT06188663.