He F J, MacGregor G A
Blood Pressure Unit, St George's Hospital Medical School, London, UK.
J Hum Hypertens. 2002 Nov;16(11):761-70. doi: 10.1038/sj.jhh.1001459.
Two recent meta-analyses of randomised salt reduction trials have concluded that there is little purpose in reducing salt intake in the general population. However, the authors, as with other previous meta-analyses, included trials of very short duration (eg 1 week or less) and trials of acute salt loading followed by abrupt reductions to very low salt intake (eg from 20 to less than 1 g of salt/day). These acute salt loading and salt depletion experiments are known to increase sympathetic tone, and with salt depletion cause a rise in renin release and, thereby, plasma angiotensin II. These trials are not appropriate, therefore, for helping to inform public health policy, which is for a more modest reduction in salt intake, ie, from a usual intake of approximately 10 to approximately 5 g of salt per day over a more prolonged period of time. We carried out a meta-analysis to assess the effect of a modest salt reduction on blood pressure. Our data sources were MEDLINE, EMBASE, Cochrane library, CINAHL, and the reference lists of original and review articles. We included randomised trials with a modest reduction in salt intake and a duration of 4 or more weeks. Meta-analysis, meta-regression, and funnel plots were performed. A total of 17 trials in hypertensives (n=734) and 11 trials in normotensives (n=2220) were included in our study. The median reduction in 24-h urinary sodium excretion was 78 mmol (equivalent to 4.6 g of salt/day) in hypertensives and 74 mmol in normotensives. The pooled estimates of blood pressure fall were 4.96/2.73+/-0.40/0.24 mmHg in hypertensives (P<0.001 for both systolic and diastolic) and 2.03/0.97+/-0.27/0.21 mmHg in normotensives (P<0.001 for both systolic and diastolic). Weighted linear regression analyses showed a dose response between the change in urinary sodium and blood pressure. A reduction of 100 mmol/day (6 g of salt) in salt intake predicted a fall in blood pressure of 7.11/3.88 mmHg (P<0.001 for both systolic and diastolic) in hypertensives and 3.57/1.66 mmHg in normotensive individuals (systolic: P<0.001; diastolic: P<0.05). Our results demonstrate that a modest reduction in salt intake for a duration of 4 or more weeks does have a significant and, from a population viewpoint, important effect on blood pressure in both hypertensive and normotensive individuals. This meta-analysis strongly supports other evidence for a modest and long-term reduction in population salt intake, and would be predicted to reduce stroke deaths immediately by approximately 14% and coronary deaths by approximately 9% in hypertensives, and reduce stroke and coronary deaths by approximately 6 and approximately 4%, in normotensives, respectively.
最近两项关于随机盐减少试验的荟萃分析得出结论，在普通人群中减少盐摄入量几乎没有意义。然而，与之前的其他荟萃分析一样，作者纳入了持续时间非常短的试验（例如1周或更短）以及急性盐负荷试验，随后突然将盐摄入量降至极低水平（例如从每天20克降至不足1克）。已知这些急性盐负荷和盐耗竭实验会增加交感神经张力，并且随着盐耗竭会导致肾素释放增加，从而使血浆血管紧张素II升高。因此，这些试验不适用于为公共卫生政策提供参考，公共卫生政策是在更长时间内将盐摄入量适度减少，即从通常每天约10克盐减少到约5克盐。我们进行了一项荟萃分析，以评估适度减少盐摄入量对血压的影响。我们的数据来源是医学文献数据库（MEDLINE）、荷兰医学文摘数据库（EMBASE）、考科蓝图书馆、护理学与健康领域数据库（CINAHL）以及原始文章和综述文章的参考文献列表。我们纳入了盐摄入量适度减少且持续时间为4周或更长时间的随机试验。进行了荟萃分析、荟萃回归和漏斗图分析。我们的研究共纳入了17项高血压患者试验（n = 734）和11项血压正常者试验（n = 2220）。高血压患者中尿钠排泄量24小时的中位数减少量为78毫摩尔（相当于每天4.6克盐），血压正常者中为74毫摩尔。高血压患者血压下降的合并估计值为4.96/2.73±0.40/0.24 mmHg（收缩压和舒张压P均<0.001），血压正常者中为2.03/0.97±0.27/0.21 mmHg（收缩压和舒张压P均<0.001）。加权线性回归分析显示尿钠变化与血压之间存在剂量反应关系。盐摄入量每天减少100毫摩尔（6克盐）预计高血压患者血压下降7.11/3.88 mmHg（收缩压和舒张压P均<0.001），血压正常者血压下降3.57/1.66 mmHg（收缩压：P<0.001；舒张压：P<0.05）。我们的结果表明，持续4周或更长时间适度减少盐摄入量对高血压患者和血压正常者的血压确实有显著且从人群角度来看很重要的影响。这项荟萃分析有力地支持了其他关于适度长期减少人群盐摄入量的证据，预计可使高血压患者的中风死亡率立即降低约14%，冠心病死亡率降低约9%，血压正常者的中风和冠心病死亡率分别降低约6%和约4%。
