These investigators quantified sodium intake in 66 countries (accounting for 74% of adults throughout the world) by age, sex, and country of residence, and correlated these data first with findings from their meta-analysis of 107 randomized trials of interventions to curb sodium intake and then with the results of two large international trials linking the effects of various blood pressure levels on CV mortality.
They estimated that the mean level of sodium intake worldwide is 3.95 g/day and that those mean levels varied by geographic region from a low of 2.18 g to a high of 5.51 g. "Overall, 181 of 187 countries – 99.2% of the adult population of the world – had estimated mean levels of sodium intake exceeding the World Health Organization recommendation of 2.0 g/day," Dr. Mozaffarian and his associates said.
Contrary to the findings of the two PURE analyses, these data showed "strong evidence of a linear dose-response relationship" between sodium intake and blood pressure, such that each reduction of 2.30 g/day of sodium was significantly linked with a reduction of 3.82 mm Hg in systolic blood pressure, as well as a direct correlation between increasing blood pressure and increasing CV mortality.
Extrapolating from these data, "we found that 1.65 million deaths from CV causes worldwide in 2010 were attributable to sodium consumption above the reference level" of 2 g/day. "Globally, 40.4% of these deaths occurred prematurely, i.e. in persons younger than 70 years of age," Dr. Mozaffarian and his associates said (N. Engl. J. Med. 2014 Aug. 14;371:624-34 [doi:10.1056/NEJMoa1304127]).
"In sum, approximately 1 of every 10 deaths from CV causes worldwide and nearly 1 of every 5 premature deaths from CV causes were attributed to sodium consumption above the reference level," they said.
In an editorial accompanying this report, Dr. Suzanne Oparil said, "The NUTRICODE investigators should be applauded for a herculean effort in synthesizing a large body of data regarding the potential harm of excess salt consumption" (N. Engl. J. Med. 2014 Aug. 14;371:677-9 [doi:10.1056/NEJMe1407695]).
"However, given the numerous assumptions necessitated by the lack of high-quality data [in the literature], caution should be taken in interpreting the findings of this study," said Dr. Oparil of the vascular biology and hypertension program, University of Alabama at Birmingham.
The PURE studies were supported by the Heart and Stroke Foundation of Ontario, the Population Health Research Institute, the Canadian Institutes of Health Research, several pharmaceutical companies, and various national or local organizations in 18 participating countries. These funders played no role in the design or conduct of the studies, in collection or analysis of data, or in preparing the manuscript. Dr. O’Donnell reported ties to Boehringer Ingelheim, Bayer, Bristol-Myers Squibb, and Pfizer, and his associates reported ties to Sanofi-Aventis, AstraZeneca, and Cadila. The NUTRICODE study was funded by the Bill and Melinda Gates Foundation.