Adler Alma J, Taylor Fiona, Martin Nicole, Gottlieb Sheldon, Taylor Rod S, Ebrahim Shah
Department of Non-communicable Disease Epidemiology, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
Cochrane Database Syst Rev. 2014 Dec 18;2014(12):CD009217. doi: 10.1002/14651858.CD009217.pub3.
This is an update of a Cochrane review that was first published in 2011 of the effects of reducing dietary salt intake, through advice to reduce salt intake or low-sodium salt substitution, on mortality and cardiovascular events.
We updated the searches of CENTRAL (2013, Issue 4), MEDLINE (OVID, 1946 to April week 3 2013), EMBASE (OVID, 1947 to 30 April 2013) and CINAHL (EBSCO, inception to 1 April 2013) and last ran these on 1 May 2013. We also checked the references of included studies and reviews. We applied no language restrictions.
Trials fulfilled the following criteria: (1) randomised, with follow-up of at least six months, (2) the intervention was reduced dietary salt (through advice to reduce salt intake or low-sodium salt substitution), (3) participants were adults and (4) mortality or cardiovascular morbidity data were available. Two review authors independently assessed whether studies met these criteria.
A single author extracted data and assessed study validity, and a second author checked this. We contacted trial authors where possible to obtain missing information. We extracted events and calculated risk ratios (RRs) and 95% confidence intervals (CIs).
Eight studies met the inclusion criteria: three in normotensives (n = 3518) and five in hypertensives or mixed populations of normo- and hypertensives (n = 3766). End of trial follow-up ranged from six to 36 months and the longest observational follow-up (after trial end) was 12.7 years.The risk ratios (RR) for all-cause mortality in normotensives were imprecise and showed no evidence of reduction (end of trial RR 0.67, 95% confidence interval (CI) 0.40 to 1.12, 60 deaths; longest follow-up RR 0.90, 95% CI 0.58 to 1.40, 79 deaths n=3518) or in hypertensives (end of trial RR 1.00, 95% CI 0.86 to 1.15, 565 deaths; longest follow-up RR 0.99, 95% CI 0.87 to 1.14, 674 deaths n=3085). There was weak evidence of benefit for cardiovascular mortality (hypertensives: end of trial RR 0.67, 95% CI 0.45 to 1.01, 106 events n=2656) and for cardiovascular events (hypertensives: end of trial RR 0.76, 95% CI 0.57 to 1.01, 194 events, four studies, n = 3397; normotensives: at longest follow-up RR 0.71, 95% CI 0.42 to 1.20, 200 events; hypertensives: RR 0.77, 95% CI 0.57 to 1.02, 192 events; pooled analysis of six trials RR 0.77, 95% CI 0.63 to 0.95, n = 5912). These findings were driven by one trial among retirement home residents that reduced salt intake in the kitchens of the homes, thereby not requiring individual behaviour change.Advice to reduce salt showed small reductions in systolic blood pressure (mean difference (MD) -1.15 mmHg, 95% CI -2.32 to 0.02 n=2079) and diastolic blood pressure (MD -0.80 mmHg, 95% CI -1.37 to -0.23 n=2079) in normotensives and greater reductions in systolic blood pressure in hypertensives (MD -4.14 mmHg, 95% CI -5.84 to -2.43 n=675), but no difference in diastolic blood pressure (MD -3.74 mmHg, 95% CI -8.41 to 0.93 n=675).Overall many of the trials failed to report sufficient detail to assess their potential risk of bias. Health-related quality of life was assessed in one trial in normotensives, which reported significant improvements in well-being but no data were presented.
AUTHORS' CONCLUSIONS: Despite collating more event data than previous systematic reviews of randomised controlled trials, there is insufficient power to confirm clinically important effects of dietary advice and salt substitution on cardiovascular mortality in normotensive or hypertensive populations. Our estimates of the clinical benefits from advice to reduce dietary salt are imprecise, but are larger than would be predicted from the small blood pressure reductions achieved. Further well-powered studies would be needed to obtain more precise estimates. Our findings do not support individual dietary advice as a means of restricting salt intake. It is possible that alternative strategies that do not require individual behaviour change may be effective and merit further trials.
这是Cochrane系统评价的更新版，该评价首次发表于2011年，内容是关于通过减少盐摄入建议或低钠盐替代来降低饮食中盐摄入量对死亡率和心血管事件的影响。
我们更新了对Cochrane系统评价数据库（CENTRAL，2013年第4期）、医学期刊数据库（MEDLINE，OVID平台，1946年至2013年4月第3周）、荷兰医学文摘数据库（EMBASE，OVID平台，1947年至2013年4月30日）和护理学与健康领域数据库（CINAHL，EBSCO平台，建库至2013年4月1日）的检索，最后一次检索时间为2013年5月1日。我们还检查了纳入研究和综述的参考文献。我们未设语言限制。
试验需满足以下标准：（1）随机分组且随访至少6个月；（2）干预措施为减少饮食中的盐摄入量（通过减少盐摄入建议或低钠盐替代）；（3）参与者为成年人；（4）有死亡率或心血管疾病发病率数据。两位综述作者独立评估研究是否符合这些标准。
由一位作者提取数据并评估研究的有效性，另一位作者进行核对。我们尽可能与试验作者联系以获取缺失信息。我们提取事件并计算风险比（RR）和95%置信区间（CI）。
八项研究符合纳入标准：三项针对血压正常者（n = 3518），五项针对高血压患者或血压正常与高血压混合人群（n = 3766）。试验随访期从6个月至36个月不等，最长的观察性随访（试验结束后）为12.7年。血压正常者全因死亡率的风险比（RR）不精确，未显示出降低的证据（试验结束时RR为0.67，95%置信区间（CI）为0.40至1.12，60例死亡；最长随访期RR为0.90，95%CI为0.58至1.40，79例死亡，n = 3518），高血压患者中也未显示出降低的证据（试验结束时RR为1.00，95%CI为0.86至1.15，565例死亡；最长随访期RR为0.99，95%CI为0.87至1.14，674例死亡，n = 3085）。有微弱证据表明对心血管死亡率有益（高血压患者：试验结束时RR为0.67，95%CI为0.45至1.01，106例事件，n = 2656）以及对心血管事件有益（高血压患者：试验结束时RR为0.76，95%CI为0.57至1.01，194例事件，四项研究，n = 3397；血压正常者：最长随访期RR为0.71，95%CI为0.42至1.20，200例事件；高血压患者：RR为0.77，95%CI为0.57至1.02，192例事件；六项试验的汇总分析RR为0.77，95%CI为0.63至0.95，n = 5912）。这些结果是由一项针对养老院居民的试验推动的，该试验减少了养老院厨房中的盐摄入量，因此无需个人行为改变。减少盐摄入的建议使血压正常者的收缩压有小幅降低（平均差（MD）为 -1.15 mmHg，95%CI为 -2.32至0.02，n = 2079），舒张压也有小幅降低（MD为 -0.80 mmHg，95%CI为 -1.37至 -0.23，n = 2079），高血压患者的收缩压降低幅度更大（MD为 -4.14 mmHg，95%CI为 -5.84至 -2.43，n = 675），但舒张压无差异（MD为 -3.74 mmHg，95%CI为 -8.41至0.93，n = 675）。总体而言，许多试验未能报告足够详细的信息来评估其潜在的偏倚风险。在一项针对血压正常者的试验中评估了与健康相关的生活质量，该试验报告幸福感有显著改善，但未提供数据。
尽管与之前对随机对照试验的系统评价相比，我们整理了更多的事件数据，但仍没有足够的证据来证实饮食建议和盐替代对血压正常或高血压人群心血管死亡率的临床重要影响。我们对减少饮食中盐摄入建议的临床益处的估计并不精确，但比通过小幅降低血压所预测的要大。需要进一步开展有足够效力的研究以获得更精确的估计。我们的研究结果不支持将个人饮食建议作为限制盐摄入的一种手段。可能不需要个人行为改变的替代策略可能有效，值得进一步试验。
