PURE study results link sodium intake to BP, mortality, CV events

An approximate sodium intake of 3 to 6 grams per day is correlated with decreased risk for mortality and CV events compared with intake levels either above or below this range, according to findings from the PURE study.

In a separate analysis of PURE data, researchers also found that the relationship between sodium/potassium intake and BP is strongest among those with high sodium intake, older age and hypertension.

Impact of sodium intake on mortality, CV events

The PURE study is a large-scale, epidemiological cohort study that evaluated individuals throughout 628 urban and rural regions in countries of varying income levels.

In one analysis, researchers assessed 101,945 participants across 17 countries. Fasting urine samples were collected and evaluated for sodium and potassium excretion as a surrogate for intake. Patients were followed for a mean of 3.7 years for incidence of major CV events and mortality, with a composite of all-cause mortality and death from CV events as the primary outcome. The mean estimated sodium excretion was 4.93 g/day, while potassium excretion was 2.12 g/day.

The composite primary outcome occurred in 3.3% of patients.

Compared with patients whose sodium intake fell within the reference range of an estimate of 4-5.99 g/day, those with higher estimated sodium excretion (7 g/day or more) had an increased risk for the composite outcome (OR=1.15; 95% CI, 1.02-1.3), as well as for each outcome individually.

The relationship between elevated estimated sodium excretion and the composite outcome was most pronounced among patients with hypertension (P=.02 for interaction); particularly those with an estimated sodium excretion of 6 g/day or more. Participants with estimated sodium excretion below 3 g/day were also at increased risk for the composite outcome compared with those with excretion within the reference range (OR=1.27; 95% CI, 1.12-1.44). Higher potassium excretion was associated with a decreased risk for the composite outcome compared with excretion estimated at fewer than 1.5 g/day.

While concluding that sodium intake within the 3 g/day to 6 g/day range was associated with lower risk for mortality and CV events than either higher or lower intake, the researchers cautioned against interpreting their results as a mandate to lower sodium intake.

“Our study provides an epidemiologic comparison of groups that consume different levels of sodium, and it does not provide information on the effect on clinical outcomes of reducing sodium intake,” the authors wrote. “Therefore, our findings should not be interpreted as evidence that the intentional reduction of sodium intake would alter the risk of death or [CVD].”

Sodium, potassium and BP

In a separate analysis, researchers sought to determine the impact of sodium and potassium intake on BP as influenced by geographic region and demographic factors. They evaluated BP measurements from 102,216 adults aged 35 to 70 years across 18 countries. The participants provided samples of morning fasting urine, which was evaluated for estimated 24-hour sodium and potassium excretion.

The researchers observed incremental increases of 2.11 mm Hg in systolic BP and 0.78 mm Hg in diastolic BP for each 1 g/day increase in estimated sodium excretion. The slope of this association increased with sodium intake, with a 2.58 mm Hg systolic BP increase per gram among those with excretion >5 g/day, compared with 0.74 mm Hg per gram among those with <3 g/day. The gradient of association was also steeper among those aged older than 55 years (2.97 mm Hg per gram increase vs. 1.96 mm Hg per gram at <45 years of age) and participants with hypertension (2.49 mm Hg per gram vs. 1.3 mm Hg per gram among nonhypertensive patients) (P<.001 for all interactions).

They found that potassium excretion was inversely associated with systolic BP, with a steeper slope of association for those with hypertension and older people (P<.001 for both).

The authors acknowledged that they did not assess the impact of changing sodium or potassium intake on BP. “However, our findings do suggest that assessments of the relationship between sodium intake and [BP] should take into account the level of sodium intake in the population, the age of the participants and whether the participants have hypertension,” they wrote.

For more information:

Mente A. N Engl J Med. 2014;371:601-611.

O’Donnell M. N Engl J Med. 2014;371:612-623.

Disclosure: See the full studies for relevant financial disclosures.