Effects of blood pressure lowering on outcome incidence in hypertension: 2. Effects at different baseline and achieved blood pressure levels--overview and meta-analyses of randomized trials.J Hypertens 2014; 32(12):2296-304JH
Relevant clinical questions not approached by randomized controlled trials (RCTs) of blood pressure (BP)-lowering treatment can be explored by meta-analyses stratified by clinical criteria.
Investigating whether all grades of hypertension benefit from BP-lowering treatment and which are the target BP levels to maximize outcome reduction.
Of the 68 RCTs of intentional and nonintentional BP-lowering, those without baseline antihypertensive drugs were stratified by the average baseline SBP and DBP (hypertension grades 1, 2, and 3). RCTs with or without baseline treatment were considered for investigating the effects of mean achieved SBP/DBP across three SBP cutoffs and two DBP cutoffs. Risk ratios (RR) and 95% confidence interval (CI) (random-effects model), standardized to 10/5 mmHg SBP/DBP reduction, and absolute risk reductions of seven fatal and nonfatal outcomes were calculated. Differences between relative and absolute risk reductions in the different strata of baseline or achieved SBP/DBP were evaluated by trend or heterogeneity analyses.
In 32 RCTs (104,359 individuals), significant outcome reductions were found independently of the hypertension grade, with no trend toward risk ratio changes with increasing baseline BP. A secondary analysis limited to RCTs on grade 1 hypertension at low-to-moderate risk showed significant outcome reductions [risk ratio: stroke 0.33 (0.11-0.98), coronary events 0.68 (0.48-0.95), and death 0.53 (0.35-0.80)]. In 32 RCTs (128,232 individuals), relative and absolute outcome reductions were significant for the SBP differences across 150 and 140 mmHg cutoffs. Below 130 mmHg, only stroke and all-cause death were significantly reduced. Absolute outcome reduction showed a significant trend to decrease, the lower the SBP cutoff considered. In 29 RCTs (107,665 individuals), outcomes were significantly reduced across DBP cutoffs of 90 and 80 mmHg. After excluding RCTs with baseline DBP less than 90 mmHg, only stroke reduction was significant at achieved DBP less than 80 mmHg.
Meta-analyses favor BP-lowering treatment even in grade 1 hypertension at low-to-moderate risk, and lowering SBP/DBP to less than 140/90 mmHg. Achieving less than 130/80 mmHg appears safe, but only adds further reduction in stroke.