The Dietary Approaches to Stop Hypertension (DASH) diet is recognized as an effective dietary intervention to reduce blood pressure (BP). However, among randomized controlled trials (RCTs) investigating the DASH diet-mediated BP reduction, there are significant methodological and clinical differences. The purpose of this study was to comprehensively assess the DASH diet effect on BP in adults with and without hypertension, accounting for underlying methodological and clinical confounders. We systematically searched Medline and the Cochrane Collaboration Library databases and identified 30 RCTs (n = 5545 participants) that investigated the BP effects of the DASH diet compared with a control diet in hypertensive and nonhypertensive adults. Both random-effects and fixed-effect models were used to calculate the mean attained systolic BP (SBP) and diastolic BP (DBP) differences during follow-up. Subgroup and meta-regression analyses were also conducted. Compared with a control diet, the DASH diet reduced both SBP and DBP (difference in means: -3.2 mm Hg; 95% CI: -4.2, -2.3 mm Hg; P < 0.001, and -2.5 mm Hg; 95% CI: -3.5, -1.5 mm Hg; P < 0.001, respectively). Hypertension status did not modify the effect on BP reduction. The DASH diet compared with a control diet reduced SBP levels to a higher extent in trials with sodium intake >2400 mg/d than in trials with sodium intake ≤2400 mg/d, whereas both SBP and DBP were reduced more in trials with mean age <50 y than in trials of older participants. The quality of evidence was rated as moderate for both outcomes according to the Grading of Recommendations, Assessment, Development, and Evaluation approach. The adoption of the DASH diet was accompanied by significant BP reduction in adults with and without hypertension, although higher daily sodium intake and younger age enhanced the BP-lowering effect of the intervention. This meta-analysis was registered at www.crd.york.ac.uk/prospero as CRD42019128120.

Antihypertensive treatment is based on randomized controlled trials (RCTs) started since 1966. Meta-analyses comprehensive of all RCTs but limited to RCTs investigating blood pressure (BP) lowering in hypertensive patients are lacking. Two clinical questions were investigated: the extent of different outcome reductions by BP lowering in hypertensive patients, and the proportionality of outcome reductions to SBP, DBP, and pulse pressure (PP) reductions. PubMed between 1966 and December 2013 (any language), Cochrane Collaboration Library and previous overviews were used as data sources for identifying and selecting all RCTs comparing the antihypertensive drugs with placebo or less intense BP lowering (intentional BP-lowering RCTs); comparing BP-lowering drugs with placebo without BP-lowering intention, but with BP difference (nonintentional BP-lowering RCTs); and enrolling at least 40% hypertensive patients. RCTs on acute myocardial infarction, heart failure, acute stroke, and dialysis were excluded. RCT quality was assessed by scoring. Risk ratios and 95% confidence interval (CI), standardized to 10/5 mmHg SBP/DBP reduction, of seven fatal and nonfatal outcomes were calculated (random-effects model). The relationships of different outcome reductions to SBP, DBP, and PP reductions were investigated by meta-regressions. A total of 68 RCTs (245,885 individuals) were eligible, of which 47 (153,825 individuals) were 'intentional' RCTs. All outcomes were reduced (P < 0.001) by BP lowering, stroke [-36% (-29, -42)], and heart failure [-43% (-28, -54)] to a greater extent, with smaller reductions for coronary events [coronary heart disease (CHD): -16% (-10, -21)], cardiovascular [-18% (-11, -24)], and all-cause mortality [-11% (-5, -16)]. Absolute risk reductions were 17 (14, 20) strokes, 28 (19, 35) cardiovascular events, and 8 (4, 12) deaths prevented every 1000 patients treated for 5 years. Logarithmic risk ratios were related to SBP, DBP, and PP reductions (P = 0.001-0.003) for stroke and composite cardiovascular events, but not for CHD. Meta-analyses of all BP-lowering RCTs involving hypertensive patients provide precise estimates of benefits (larger for stroke and heart failure, but also significant for CHD and mortality). Absolute risk reductions are substantial. Relationships of logarithmic risk ratios with BP reductions imply risk reduction increases progressively to a smaller extent the larger the BP reduction.

Previous meta-analyses of our group have investigated the cardiovascular effects of more vs. less intense blood pressure (BP) treatment and the BP levels to be achieved by treatment. A few additional trials have been completed recently, particularly the large SPRINT study. Updating of the previous meta-analyses has been done with the objective of further clarifying the practical question of BP targets of antihypertensive treatment. Among randomized-controlled trials (RCTs) of BP lowering treatment between 1966 and 2015, 16 (52 235 patients) compared more vs. less intense treatment and fulfilled other preset criteria, and in 34 (138 127 patients) SBP in the active (vs. placebo) or the more (vs. less) intense treatment was below (vs., respectively, above) three predetermined cutoffs. For their meta-analyses risk ratios (RR) and 95% confidence intervals, standardized to -10/-5 mmHg SBP/DBP reduction, and absolute risk reductions of seven fatal and nonfatal outcomes were calculated. More intense BP lowering significantly reduced risk of stroke [RR 0.71 (0.60-0.84)], coronary events [0.80 (0.68-0.95)], major cardiovascular events [0.75 (0.68-0.85)] and cardiovascular mortality [0.79 (0.63-0.97)], but not heart failure and all-cause death. When the 16 RCTs were stratified according to cardiovascular death risk, relative risk reduction did not differ between strata, but absolute risk reduction increased with cardiovascular risk, though the residual risk also increased. Stratification of the 34 RCTs according to the three different SBP cutoffs (150, 140 and 130 mmHg) showed that a SBP/DBP difference of -10/-5 mmHg across each cutoff significantly reduced risk of all outcomes to the same proportion (relative risk reduction), but absolute risk reduction of most outcomes had a significant trend to decrease at lower cutoffs. Updating of previous meta-analyses indicates that more vs. less intense BP lowering can reduce not only stroke and coronary events, but also cardiovascular mortality. Including data from recent RCTs also shows that all major outcomes can be reduced by lowering SBP a few mmHg below vs. above 130 mmHg, but absolute risk reduction becomes smaller, suggesting patients at lower initial SBP were at a lower level of cardiovascular risk.