Effect of dietary salt restriction on central blood pressure: A systematic review and meta-analysis of the intervention studies

Abstract

Central blood pressure (cBP) is highly associated with cardiovascular risk. Although reduction of salt intake leads to lower peripheral blood pressure (BP), the studies on cBP provided inconsistent results. Therefore, we performed a systematic review and a meta-analysis of the available intervention trials of salt reduction on cBP values to reach definitive conclusions. A systematic search of the online databases available (up to December 2018) was conducted including the intervention trials that reported non-invasively assessed cBP changes after two different salt intake regimens. For each study, the mean difference and 95% confidence intervals were pooled using a random-effect model. Sensitivity, heterogeneity, publication bias, subgroup, and meta-regression analyses were performed. Fourteen studies met the pre-defined inclusion criteria and provided 17 cohorts with 457 participants with 1-13 weeks of intervention time. In the pooled analysis, salt restriction was associated with a significant reduction in augmentation index (9.3%) as well as central systolic BP and central pulse pressure. There was a significant heterogeneity among studies (I² = 70%), but no evidence of publication bias. Peripheral BP changes seemed to partially interfere on the relationship between salt restriction and cBP. The results of this meta-analysis indicate that dietary salt restriction reduces cBP. This effect seems to be, at least in part, independent of the changes in peripheral BP.

Keywords: augmentation index; central blood pressure; meta-analysis; pulse wave analysis; salt; sodium intake.

FIGURE 1

Stepwise procedure for selection of the studies. Flowchart indicating the results of the systematic review with inclusions and exclusions

FIGURE 2

A, Effect of lower sodium intake on augmentation index (AIx). Forest plot of the effect of lower dietary sodium intake on AIx in 17 population cohorts from 14 published studies. B, Effect of lower sodium intake on central systolic blood pressure (cSBP). Forest plot of the effect of lower dietary salt intake on cSBP in eight population cohorts from six published studies. C, Effect of lower sodium intake on central pulse pressure (cPP). Forest plot of the effect of lower dietary sodium intake on cPP in seven population cohorts from five published studies. Results are expressed as mean difference (MD) and 95% confidence intervals (95% CI). Squares indicate study‐specific relative risk estimates (size of the square reflects the study‐specific statistical weight); horizontal lines indicate 95% CI; and diamond indicates the overall relative risk with its 95% CI. fHP, formerly healthy pregnant women; fPE, formerly pre‐eclamptic women; SS, salt‐sensitive participants; SR, salt‐resistant participants; YG, young participants; MA, middle‐aged participants