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Intervention Review

Effect of longer-term modest salt reduction on blood pressure

  1. Feng J He,
  2. Graham A MacGregor*

Editorial Group: Cochrane Hypertension Group

Published Online: 26 JAN 2004

Assessed as up-to-date: 8 MAY 2005

DOI: 10.1002/14651858.CD004937


How to Cite

He FJ, MacGregor GA. Effect of longer-term modest salt reduction on blood pressure. Cochrane Database of Systematic Reviews 2004, Issue 1. Art. No.: CD004937. DOI: 10.1002/14651858.CD004937.

Author Information

  1. St. George's Hospital Medical School, Blood Pressure Unit, London, UK

*Graham A MacGregor, Blood Pressure Unit, St. George's Hospital Medical School, Cranmer Terrace, London, SW17 0RE, UK. g.macgregor@sghms.ac.uk.

Publication History

  1. Publication Status: Edited (no change to conclusions)
  2. Published Online: 26 JAN 2004

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Abstract

  1. Top of page
  2. Abstract
  3. Plain language summary
  4. 摘要

Background

Many randomised trials assessing the effect of salt reduction on blood pressure show reduction in blood pressure in individuals with high blood pressure. However, there is controversy about the magnitude and the clinical significance of the fall in blood pressure in individuals with normal blood pressure. Several meta-analyses of randomised salt reduction trials have been published in the last few years. However, most of these included trials of very short duration (e.g. 5 days) and included trials with salt loading followed by salt deprivation (e.g. from 20 to 1 g/day) over only a few days. These short-term experiments are not appropriate to inform public health policy which is for a modest reduction in salt intake over a prolonged period of time. A meta-analysis (Hooper 2002) is an important attempt to look at whether advice to achieve a long-term salt reduction (i.e. more than 6 months) in randomised trials causes a fall in blood pressure. However, most trials included in this meta-analysis achieved a small reduction in salt intake; on average, salt intake was reduced by 2 g/day. It is, therefore, not surprising that this analysis showed a small fall in blood pressure, and that a dose-response to salt reduction was not demonstrable.

Objectives

To assess the effect of the currently recommended modest salt reduction on blood pressure in individuals with elevated and normal blood pressure.
To assess whether there is a dose-response to salt reduction.

Search methods

We searched MEDLINE, EMBASE, Cochrane library and reference list of original and review articles.

Selection criteria

We included randomised trials with a modest reduction in salt intake and duration of 4 or more weeks.

Data collection and analysis

Data were extracted independently by two persons. Mean effect sizes were calculated using both fixed and random effects model. Weighted linear regression was performed to examine the relationship between the change in urinary sodium and the change in blood pressure.

Main results

Twenty trials in individuals with elevated blood pressure (n=802) and 11 trials in individuals with normal blood pressure (n=2220) were included. In individuals with elevated blood pressure the median reduction in urinary sodium was 78 mmol/24h (4.6 g/day of salt), the mean reduction in blood pressure was -5.06 mmHg (95%CI:-5.81 to -4.31) for systolic and -2.70 mmHg (95% CI:-3.16 to -2.24) for diastolic. In individuals with normal blood pressure the median reduction in urinary sodium was 74 mmol/24h (4.4 g/day of salt), the mean reduction in blood pressure was -2.03 mmHg (95% CI: -2.56 to -1.50) for systolic and -0.99 mmHg (-1.40 to -0.57) for diastolic. Weighted linear regression showed a significant relationship between the reduction in urinary sodium and the reduction in blood pressure.

Authors' conclusions

Our meta-analysis demonstrates that a modest reduction in salt intake for a duration of 4 or more weeks has a significant and, from a population viewpoint, important effect on blood pressure in both individuals with normal and elevated blood pressure. These results support other evidence suggesting that a modest and long-term reduction in population salt intake could reduce strokes, heart attacks, and heart failure. Furthermore, our meta-analysis demonstrates a correlation between the magnitude of salt reduction and the magnitude of blood pressure reduction. Within the daily intake range of 3 to 12 g/day, the lower the salt intake achieved, the lower the blood pressure.

 

Plain language summary

  1. Top of page
  2. Abstract
  3. Plain language summary
  4. 摘要

Effect of longer-term modest salt reduction on blood pressure

Current public health recommendations in most developed countries are to reduce salt intake by about half, i.e. from approximately 10 grams per day to 5 grams per day. Our pooled analysis of randomised trials of 4 weeks or more in duration showed that reduction in salt intake lowers blood pressure both in individuals with elevated blood pressure and in those with normal blood pressure. These results support other evidence for a modest and long term reduction in population salt intake. If this occured it would result in a lower population blood pressure, and a reduction in strokes, heart attacks and heart failure. Furthermore, our study is consistent with the fact that the lower the salt intake, the lower the blood pressure. The current recommendations to reduce salt intake to 5 grams per day will lower blood pressure, but a further reduction to 3 grams per day will lower blood pressure more.

 

摘要

  1. Top of page
  2. Abstract
  3. Plain language summary
  4. 摘要

背景

長期適度鹽份限制對血壓的效果

很多隨機試驗評估對於減少鹽份攝取對於血壓的效果,結果顯示這些高血壓患者可以降低血壓。然而對於試驗的規模及血壓正常人的降壓效果仍有爭議。幾個對於多個隨機鹽份減少攝取試驗的統合分析(metaanalyses)在過去幾年已經發表。但是被包含其中的大多數試驗有太短的追蹤期間(例如5天),另外有一些試驗則是在幾天內面臨了大量鹽份攝取後接著又嚴格限制鹽份(例如從每天20克到1克)。這些短期的實驗對於長期適當的鹽份攝取的國家衛生政策的報告提供是不夠的。Hooper 2002 是一個在達到降血壓效果的多個隨機試驗中去尋求有無長期鹽份限制(例如超過6個月)的一些建議的重要嚐試。然而,包含在這個統合分析的大多數的試驗只達到少量的鹽份攝取限制;平均鹽份攝取減少到每天2克。因此,不令人意外的這個統合分析顯示輕度的降血壓效果而鹽份的劑量相關的效果反應(doseresponse)並沒有結論。

目標

分析目前高血壓及血壓正常的人所建議的鹽份限制的效果。評估是否有劑量相關的效果反應反應(doseresponse)。

搜尋策略

我們搜尋了MEDLINE, EMBASE, Cochrane library 及reference list中的原創性文章及評論性文章。

選擇標準

我們納入了適當鹽限制及追蹤4週或大於4週的隨機試驗。

資料收集與分析

資料由2位不同人所獨立節選。平均效果的大小由使用固定及隨機效果模式所計算。Weighted linear regression 被使用來檢查尿中鹽份及血中血壓變化的相關性。

主要結論

20個在高血壓患者的試驗(n = 802)和11個正常血壓人群的試驗(n = 2220)被含括進來。高血壓患者平均尿中減少的鹽份為78 mmol/24h (鹽份每天 4.6 克),平均血壓降低收縮壓 −5.06 毫米汞柱(95% 信賴區間:−5.81 to −4.31),舒張壓 −2.70 毫米汞柱(95% 信賴區間::−3.16 to −2.24)。在血壓正常的人群,平均尿中減少的鹽份為74 mmol/24h (鹽份每天 4.4 克),平均血壓降低收縮壓 −2.03 毫米汞柱(95% 信賴區間:−2.56 to −1.50),舒張壓 −0.99 毫米汞柱(95% 信賴區間::−1.40 to −0.57)。Weighted linear regression 顯示尿中鹽份的減少與血壓的減少有顯著的相關性。

作者結論

透過大眾的觀點,我們的統合分析顯示在經過4週或大於4週地適當減少鹽份攝取,對於血壓正常或是高血壓的人可以達到一個血壓控制上明顯和重要的效果。這些結果支持對於長期減少鹽份攝取可以減少腦中風,心肌缺氧或梗塞(heart attacks),及心臟衰竭。更進一步來說,我們的統合分析顯示鹽份攝取減少的量與血壓下降的程度是有相關性的。在每天攝取3 – 12 克的範圍內,愈低的鹽份攝取,可以達到愈低的血壓。

翻譯人

本摘要由臺北榮民總醫院郭政裕翻譯。

此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。

總結

目前的大眾健康政策建議,已開發國家要減低鹽份攝取至一半,例如大約每天10克減少至5克。我們的對於這些在在血壓正常或是高血壓的人經過4週或大於4週的追蹤期間,減少鹽份攝取可以達到降血壓的效果。這些結果支持其它對於大眾適度且長期減少鹽份攝取的證據。如果可以這樣作是可以達到降低大眾血壓,減少腦中風,心肌缺氧或梗塞(heart attacks),及心臟衰竭。更進一步來看,我們的研究證實愈低的鹽份攝取可以達到愈低的血壓。目前的建議是每天鹽份攝取5克可以降低血壓,但是每天3克可以達到更好的降壓效果。