The use of lower blood pressure targets for people with hypertension

Background

We conducted this review to find and assess all trials designed to evaluate whether lower blood pressure targets are better than standard blood pressure targets for people with hypertension. 

The main objective in the treatment of hypertension is to prevent serious vascular complications. For the general population of people with hypertension, the standard treatment target has been to achieve a blood pressure of less than 140/90 mm Hg. Some clinical guidelines have recommended stricter control of blood pressure based on the assumption that achieving a lower blood pressure will produce a greater reduction in cardiovascular events.

Study Characteristics

The evidence is current to May 2019. We included 11 randomised controlled trials involving 38,688 adult participants with arterial hypertension, aged between 20 and 80 years of age, who received treatment aimed to lower blood pressure to a standard compared to a lower blood pressure target and followed for mean 3.7 years to detect differences in mortality and adverse events.

Key Results

The only significant benefits in the group assigned to 'lower' blood pressure targets was a small reduction in the incidence of heart attack and a small reduction in the incidence of congestive heart failure. However, the lower target group had an increase in the number of other serious adverse events. High-certainty evidence showed there was no difference in death from any cause or total serious adverse events with lower as compared to standard blood pressure targets. .

For the general population of persons with elevated blood pressure the small benefits of trying to achieve a lower blood pressure target rather than a standard target (≤ 140/90 mm Hg) do not outweigh the harms. Further research is needed to see if some groups of patients would benefit or be harmed by lower targets.

Authors' conclusions: 

For the general population of persons with elevated blood pressure, the benefits of trying to achieve a lower blood pressure target rather than a standard target (≤ 140/90 mm Hg) do not outweigh the harms associated with that intervention. Further research is needed to see if some groups of patients would benefit or be harmed by lower targets. The results of this review are primarily applicable to older people with moderate to high cardiovascular risk. They may not be applicable to other populations.

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Background: 

This is the first update of this review first published in 2009. When treating elevated blood pressure, doctors usually try to achieve a blood pressure target. That target is the blood pressure value below which the optimal clinical benefit is supposedly obtained. “The lower the better” approach that guided the treatment of elevated blood pressure for many years was challenged during the last decade due to lack of evidence from randomised trials supporting that strategy. For that reason, the standard blood pressure target in clinical practice during the last years has been less than 140/90 mm Hg for the general population of patients with elevated blood pressure. However, new trials published in recent years have reintroduced the idea of trying to achieve lower blood pressure targets. Therefore, it is important to know whether the benefits outweigh harms when attempting to achieve targets lower than the standard target.

Objectives: 

The primary objective was to determine if lower blood pressure targets (any target less than or equal to 135/85 mm Hg) are associated with reduction in mortality and morbidity as compared with standard blood pressure targets (less than or equal to 140/ 90 mm Hg) for the treatment of patients with chronic arterial hypertension.

The secondary objectives were: to determine if there is a change in mean achieved systolic blood pressure (SBP) and diastolic blood pressure (DBP associated with "lower targets" as compared with "standard targets" in patients with chronic arterial hypertension; and to determine if there is a change in withdrawals due to adverse events with "lower targets" as compared with "standard targets", in patients with elevated blood pressure.

Search strategy: 

The Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to May 2019: the Cochrane Hypertension Specialised Register, CENTRAL (2019, Issue 4), Ovid MEDLINE, Ovid Embase, the WHO International Clinical Trials Registry Platform, and ClinicalTrials.gov. We also contacted authors of relevant papers regarding further published and unpublished work. The searches had no language restrictions.

Selection criteria: 

Randomised controlled trials (RCTs) comparing patients allocated to lower or to standard blood pressure targets (see above).

Data collection and analysis: 

Two review authors (JAA, VL) independently assessed the included trials and extracted data. Primary outcomes were total mortality; total serious adverse events; myocardial infarction, stroke, congestive heart failure, end stage renal disease, and other serious adverse events. Secondary outcomes were achieved mean SBP and DBP, withdrawals due to adverse effects, and mean number of antihypertensive drugs used. We assessed the risk of bias of each trial using the Cochrane risk of bias tool and the certainty of the evidence using the GRADE approach. 

Main results: 

This update includes 11 RCTs involving 38,688 participants with a mean follow-up of 3.7 years. This represents 7 new RCTs compared with the original version.

At baseline the mean weighted age was 63.1 years and the mean weighted blood pressure was 155/91 mm Hg.

Lower targets do not reduce total mortality (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.86 to 1.05; 11 trials, 38,688 participants; high-certainty evidence) and do not reduce total serious adverse events (RR 1.04, 95% CI 0.99 to 1.08; 6 trials, 18,165 participants; moderate-certainty evidence). This means that the benefits of lower targets do not outweigh the harms as compared to standard blood pressure targets. Lower targets may reduce myocardial infarction (RR 0.84, 95% CI 0.73 to 0.96; 6 trials, 18,938 participants, absolute risk reduction (ARR) 0.4%, number needed to treat to benefit (NNTB) 250 over 3.7 years) and congestive heart failure (RR 0.75, 95% CI 0.60 to 0.92; 5 trials, 15,859 participants, ARR 0.6%, NNTB  167 over 3.7 years) (low-certainty for both outcomes). Reduction in myocardial infarction and congestive heart failure was not reflected in total serious adverse events. This may be due to an increase in other serious adverse events (RR 1.44, 95% CI 1.32 to 1.59; 6 trials. 18,938 participants, absolute risk increase (ARI) 3%,  number needed to treat to harm (NNTH) 33 over four years) (low-certainty evidence).

Participants assigned to a "lower” target received one additional antihypertensive medication and achieved a significantly lower mean SBP (122.8 mm Hg versus 135.0 mm Hg, and a lower mean DBP (82.0 mm Hg versus 85.2 mm Hg, than those assigned to "standard target".

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