An overview of randomized trials of sodium reduction and blood pressure.

To test for effects on systolic and diastolic blood pressure and to provide precise estimates of their magnitude, we conducted an overview of randomized clinical trials that aimed to reduce the intake of sodium in human subjects. We excluded from pooled analyses trials with confounded designs, those that compared intake levels beyond the usual range in the population, and those without published reports. Two reviewers abstracted information in duplicate and differences were reconciled. Twenty-three trials with outcome data from an aggregate of 1,536 subjects were included. Data were pooled both separately for hypertensive and normotensive subjects and for all trials combined. With the use of sample size weighting, blood pressure reductions (net of controls) were 4.9 +/- 1.3/2.6 +/- 0.8 mm Hg (systolic and diastolic, respectively, with 95% confidence limits) in hypertensive subjects and 1.7 +/- 1.0/1.0 +/- 0.7 mm Hg in normotensive subjects. The combined blood pressure reductions were 2.9 +/- 0.8/1.6 +/- 0.5 mm Hg. These changes were associated with mean reduction of urinary sodium excretion ranging from 16 to 171 mmol/24 hr for individual trials. A dose-response relation across trials was found, both in normotensive and in hypertensive subjects. These results indicate that sodium reduction lowers mean blood pressure in both hypertensive and normotensive individuals for periods of at least several months. The findings are highly consistent with results of observational epidemiological studies and have implications for preventive strategies of blood pressure control.