Blood pressure targets – how low can you get?

In this blog for people with cardiovascular disease taking treatmentSomething done with the aim of improving health or relieving suffering. For example, medicines, surgery, psychological and physical therapies, diet and exercise changes. for high blood pressure, Robert Walton, a Cochrane UK Senior Fellow in General Practice, looks at the latest Cochrane evidenceCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. on what blood pressure targets to aim for, balancing the benefits of treatment against riskA way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of side effects.

Editor’s note December 2022: The evidence and guidelines have now been updated and this blog will soon be revised to reflect these changes.

So you want to stay healthy and live to a ripe old age? But the doctor says your blood pressure is too high and you have started taking medication to bring it down. What should your blood pressure be and when do you stop trying to make it lower?

These are really important questions but until recently there was very little evidence on which to base your decision. Now there is an updated Cochrane Review that could help you to decide what your blood pressure target should be (Saiz et al. 2020), so you know what goal you need to achieve to reduce the chances of problems in the future.

First let’s have a look at existing recommendations for blood pressure targets and then see where the new review takes us.

A US perspective on blood pressure

An influential report recently by the American College of Cardiology and American Heart AssociationA relationship between two characteristics, such that as one changes, the other changes in a predictable way. For example, statistics demonstrate that there is an association between smoking and lung cancer. In a positive association, one quantity increases as the other one increases (as with smoking and lung cancer). In a negative association, an increase in one quantity corresponds to a decrease in the other. Association does not necessarily mean that one thing causes the other. reflects the views of some doctors both in the US and in Europe that blood pressure targets are currently set too high (Whelton et al, 2017). Thus experts think that many people would benefit from lower blood pressures than they are currently achieving.

Aiming for lower blood pressure seems to make sense because we know from large studies in different populations that the risk of heart disease and stroke rises steadily as blood pressure increases and, although there has been some debate on the subject, people with the lowest blood pressures generally are at lowest risk (Rapsomaniki et al, 2014).

So does all that apply to people who have already had problems with cardiovascular disease who are taking blood pressure treatment?  Well the new US guidelines presume that it does and suggest that blood pressure should be kept below 130/80.  The publication of this guideline caused a stir since doctors and patients alike begin to wonder how the targets can be achieved.

Many people already take two or more drugs to control their blood pressure and would need higher doses or extra medication to move their blood pressure below the new target. With the increased medication load comes increased risk of side effects and people may want to balance the benefits in reduction of cardiovascular disease against the unwanted effects of drugs.

Are the new guidelines taken up in Europe?

To quote that famous, and oft repeated utterance by General De Gaulle when Britain was trying to join the Common Market “Non!”.  European guidelines on preventing cardiovascular disease, published in 2016, give a general target of 140/90 for blood pressure (Piepoli et al, 2016), which is substantially higher and completely out of step the US recommendations.

What about the guidance in the UK?

De Gaulle was certain that Britain did not belong in Europe and subsequent events may have proved him right.  Whilst he could reasonably say ‘I told you so’, he might be surprised that Brexit Britain is completely in harmony with its European neighbours at least in the matter of blood pressure targets.  The National Institute for Health and Care Excellence (NICE) visited the subject in 2016 and gave a general target for people taking blood pressure lowering medication of 140/90 (NICE 2016).

So where does that leave us?

This Cochrane ReviewCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research., updated in September 2020, looks specifically at whether risk of death is lower in people with cardiovascular disease who achieve lower blood pressure targets. In this review the target blood pressure was 135/85 or less.  The review went on to assess the risk of unwanted effects from blood pressure treatment by looking at the number of people who dropped out of trialsClinical trials are research studies involving people who use healthcare services. They often compare a new or different treatment with the best treatment currently available. This is to test whether the new or different treatment is safe, effective and any better than what is currently used. No matter how promising a new treatment may appear during tests in a laboratory, it must go through clinical trials before its benefits and risks can really be known. because of drug side effects.

Interestingly there was probably little or no difference in risk of death in people in the lower blood pressure target group compared to those in the standard target group. We can’t be certain about the risks of unwanted effects as the evidence was limited.

Several trials are in progress that will give us more information on this important issue:

• European Society of Hypertension-Chinese Hypertension League Stroke in Hypertension Optimal Treatment (ESH-CHL-SHOT);
• INtensive versus standard ambulatory blood pressure lowering to prevent functional DeclINe in the ElderlY (INFINITY);
• Recurrent stroke prevention clinical outcome study (RESPECTS, NCT01198496);
• Strategy of blood pressure intervention in the elderly hypertensive patients (STEP, NCT03015311).

However, based on the best evidence to date, the choice of blood pressure targets seems straightforward – perhaps we are best advised to stay closely aligned with our European neighbours!

Now let me move on to the subject of the next referendum…

Join in the conversation on Twitter with @CochraneUK or leave a comment on the blog.

References (pdf)

Robert Walton has nothing to disclose.

Editor’s note: blog updated September 2020 as the review ‘Blood pressure targets for the treatment of people with hypertension and cardiovascular disease’ was updated, with conclusions unchanged.