Sodium and blood pressure: a review of the evidence from controlled trials of sodium reduction and epidemiological studies.

Evidence from controlled trials of sodium reduction and epidemiological studies are consistent in showing that lower urinary sodium excretion is associated with lower blood pressures (BPs) and quantitatively they give similar estimates of effect. An overview of randomised controlled trials gave the estimate that a reduction in sodium excretion averaging 70 to 75 mmol per day lowered BP in hypertensives by 4.9 mmHg systolic and 2.6 mmHg diastolic (p less than .001), and by 1.7 mmHg (p less than .001) and 1.0 mmHg (p less than .01) respectively in normotensives. An overview of within-population epidemiological studies, after correction for intra-individual variability in sodium excretion, gave a pooled (simple) regression estimate that 100 mmol lower sodium was associated with BP lower by 3.7 mmHg systolic and 2.0 mmHg diastolic (p less than .001); and the corrected pooled within-centre regression estimate from INTERSALT, with adjustment for age and sex, was that 100 mmol lower sodium was associated with BP lower by 3.5 mmHg systolic and 1.5 mmHg diastolic (p less than .001), reducing to 2.2 mmHg (p less than .001) and 0.1 mmHg respectively after adjustment for other confounders. Across the centres in INTERSALT, average sodium excretion was positively and significantly related to slope of BP with age, such that 100 mmol lower sodium was associated with a 9 mmHg lower rise in systolic BP from age 25 to age 55 (p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)