Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studiesBMJ 2009; 339 doi: http://dx.doi.org/10.1136/bmj.b4567 (Published 25 November 2009) Cite this as: BMJ 2009;339:b4567
- Pasquale Strazzullo, professor of medicine1,
- Lanfranco D’Elia, clinical lecturer in medicine1,
- Ngianga-Bakwin Kandala, principal research fellow in medical statistics2,
- Francesco P Cappuccio, professor of cardiovascular medicine and epidemiology2
- 1Department of Clinical and Experimental Medicine, “Federico II” University of Naples Medical School, Naples, Italy
- 2University of Warwick, WHO Collaborating Centre for Nutrition, Warwick Medical School, Clinical Sciences Research Institute, Coventry CV2 2DX
- Correspondence to: P Strazzullo , FP Cappuccio
- Accepted 22 October 2009
Objective To assess the relation between the level of habitual salt intake and stroke or total cardiovascular disease outcome.
Design Systematic review and meta-analysis of prospective studies published 1966-2008.
Data sources Medline (1966-2008), Embase (from 1988), AMED (from 1985), CINAHL (from 1982), Psychinfo (from 1985), and the Cochrane Library.
Review methods For each study, relative risks and 95% confidence intervals were extracted and pooled with a random effect model, weighting for the inverse of the variance. Heterogeneity, publication bias, subgroup, and meta-regression analyses were performed. Criteria for inclusion were prospective adult population study, assessment of salt intake as baseline exposure, assessment of either stroke or total cardiovascular disease as outcome, follow-up of at least three years, indication of number of participants exposed and number of events across different salt intake categories.
Results There were 19 independent cohort samples from 13 studies, with 177 025 participants (follow-up 3.5-19 years) and over 11 000 vascular events. Higher salt intake was associated with greater risk of stroke (pooled relative risk 1.23, 95% confidence interval 1.06 to 1.43; P=0.007) and cardiovascular disease (1.14, 0.99 to 1.32; P=0.07), with no significant evidence of publication bias. For cardiovascular disease, sensitivity analysis showed that the exclusion of a single study led to a pooled estimate of 1.17 (1.02 to 1.34; P=0.02). The associations observed were greater the larger the difference in sodium intake and the longer the follow-up.
Conclusions High salt intake is associated with significantly increased risk of stroke and total cardiovascular disease. Because of imprecision in measurement of salt intake, these effect sizes are likely to be underestimated. These results support the role of a substantial population reduction in salt intake for the prevention of cardiovascular disease.
Contributors: PS and FPC conceived the study aims and design, contributed to the systematic review and data extraction, performed the analysis, interpreted the results, and drafted the manuscript. LD’E and N-BK contributed to the data extraction, interpretation of results, and revision of the manuscript. PS is guarantor.
Funding: This study was funded in part by an EC Grant (FP7-HEALTH- 2007-201550). The publication does not necessarily represent the decisions or the stated policy of WHO and the designations employed and the presentation of the material do not imply the expression of any opinion on the part of WHO.
Competing interests: None declared.
Ethical approval: Not required.
Data sharing: Search strategy and flow chart are available from the corresponding authors by e-mail.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.