Effect of dose and duration of reduction in dietary sodium on blood pressure levels: systematic review and meta-analysis of randomised trialsBMJ 2020; 368 doi: https://doi.org/10.1136/bmj.m315 (Published 25 February 2020) Cite this as: BMJ 2020;368:m315
- Liping Huang, doctoral candidate and data analyst1 2,
- Kathy Trieu, research fellow2,
- Sohei Yoshimura, honorary fellow and consultant stroke neurologist2 3,
- Bruce Neal, executive director and professor of clinical epidemiology2 4,
- Mark Woodward, professor of medical statistics and professor of statistics and epidemiology2 5,
- Norm R C Campbell, professor emeritus6,
- Qiang Li, senior biostatistician2,
- Daniel T Lackland, professor of epidemiology7,
- Alexander A Leung, assistant professor6,
- Cheryl A M Anderson, professor8,
- Graham A MacGregor, professor of cardiovascular medicine9,
- Feng J He, professor of global health research9
- 1Sydney School of Public Health, University of Sydney, Sydney, NSW, Australia
- 2The George Institute for Global Health, UNSW Sydney, Sydney, NSW, Australia
- 3National Cerebral and Cardiovascular Centre, Osaka, Japan
- 4Department of Epidemiology and Biostatistics, Imperial College London, London, UK
- 5The George Institute for Global Health, University of Oxford, Oxford, UK
- 6Departments of Medicine and Community Health Science, University of Calgary, Calgary, AB, Canada
- 7Medical University of South Carolina, Charleston, SC, USA
- 8The University of California, San Diego, CA, USA
- 9Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 4NS, UK
- Correspondence to: F J He
- Accepted 8 January 2020
Objective To examine the dose-response relation between reduction in dietary sodium and blood pressure change and to explore the impact of intervention duration.
Design Systematic review and meta-analysis following PRISMA guidelines.
Data sources Ovid MEDLINE(R), EMBASE, and Cochrane Central Register of Controlled Trials (Wiley) and reference lists of relevant articles up to 21 January 2019.
Inclusion criteria Randomised trials comparing different levels of sodium intake undertaken among adult populations with estimates of intake made using 24 hour urinary sodium excretion.
Data extraction and analysis Two of three reviewers screened the records independently for eligibility. One reviewer extracted all data and the other two reviewed the data for accuracy. Reviewers performed random effects meta-analyses, subgroup analyses, and meta-regression.
Results 133 studies with 12 197 participants were included. The mean reductions (reduced sodium v usual sodium) of 24 hour urinary sodium, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were 130 mmol (95% confidence interval 115 to 145, P<0.001), 4.26 mm Hg (3.62 to 4.89, P<0.001), and 2.07 mm Hg (1.67 to 2.48, P<0.001), respectively. Each 50 mmol reduction in 24 hour sodium excretion was associated with a 1.10 mm Hg (0.66 to 1.54; P<0.001) reduction in SBP and a 0.33 mm Hg (0.04 to 0.63; P=0.03) reduction in DBP. Reductions in blood pressure were observed in diverse population subsets examined, including hypertensive and non-hypertensive individuals. For the same reduction in 24 hour urinary sodium there was greater SBP reduction in older people, non-white populations, and those with higher baseline SBP levels. In trials of less than 15 days’ duration, each 50 mmol reduction in 24 hour urinary sodium excretion was associated with a 1.05 mm Hg (0.40 to 1.70; P=0.002) SBP fall, less than half the effect observed in studies of longer duration (2.13 mm Hg; 0.85 to 3.40; P=0.002). Otherwise, there was no association between trial duration and SBP reduction.
Conclusions The magnitude of blood pressure lowering achieved with sodium reduction showed a dose-response relation and was greater for older populations, non-white populations, and those with higher blood pressure. Short term studies underestimate the effect of sodium reduction on blood pressure.
Systematic review registration PROSPERO CRD42019140812.
Contributors: Members of the TRUE Consortium conceived the review. LH undertook the search. LH, KT, and SY undertook the screening for eligibility in duplicate. LH extracted all relevant data from published papers. KT and SY checked all extracted data for accuracy. MW and QL provided advice on statistical analyses. LH analysed the data and drafted the manuscript. FH and BN provided overall guidance and editing of the manuscript. All authors in the author list provided comments and feedback on the manuscript, and GM and NC also provided some guidance during the conduct of the review. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. LH and FH are the guarantors of this manuscript.
Funding: This research received no funding support.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work. Outside this work, BN has received salt substitute for trials from Salt Manufacturing Company in China and Nutek; MW is supported by the National Health and Medical Research Foundation of Australia grants (1080206 and 1149987) and receives personal fees from Amgen, personal fees from Kirin; NRCC is an unpaid member of World Action on Salt and Health and an unpaid consultant on dietary sodium and hypertension control to numerous governmental and non-governmental organisations; AAL is funded by the Hypertension Canada New Investigator Award; FJH is a member of Consensus Action on Salt and Health (CASH) and World Action on Salt and Health (WASH). Both CASH and WASH are non-profit charitable organisations and FJH does not receive any financial support from CASH or WASH; GAM is the Chairman of Blood Pressure UK (BPUK), Chairman of Consensus Action on Salt and Health (CASH) and Chairman of World Action on Salt and Health (WASH). BPUK, CASH and WASH are non-profit charitable organisations and GAM does not receive any financial support from any of these organisations.
Ethical approval: Ethical approval was not required for this research.
Data sharing: Data used for analysis have been included in this manuscript. Additional data can be obtained upon request.
The lead author (the manuscript’s guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.
Dissemination to participants and related patient and public communities: Following publication, the results of this review will be disseminated to appropriate audiences such as academia, clinicians, policy makers, and the general public, through various channels including engagement with collaborators and World Action on Salt and Health (WASH) members, press release, social media, e-newsletter, WHO Collaborating Centre on Salt Reduction website and monthly bulletin.
This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/4.0/.