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The decision to start blood pressure treatment should be based on people’s overall risk of cardiovascular disease (conditions affecting the heart or blood vessels, including heart attacks and strokes). Research based on 1 million people found that someone's overall cardiovascular risk indicated their need for blood pressure medicines more accurately than their blood pressure alone.

UK guidelines suggest that, in addition to someone's blood pressure, their overall risk should inform their decision to start drug treatment for high blood pressure. This means they need to discuss with their doctor their family history of cardiovascular disease, cholesterol (fatty substance in the blood), smoking status, and other factors, including blood pressure.

But in practice, decisions about starting on blood pressure lowering drugs are usually based on blood pressure readings. This research found that these cut-off limits made little difference to people’s chances of cardiovascular events (such as heart attack or stroke). Rising blood pressure levels only slightly increased the chances of an event among people with a similar overall risk. However, rising overall risk scores markedly increased events among people with similar blood pressure levels.

The researchers say that overall risk should play an important role in blood pressure management. This could mean that some people not currently prescribed blood pressure medicine might benefit from it. However, more research is needed into the benefits and harms of blood pressure medication in people with normal blood pressure readings.

In the meantime, doctors and people can look at their overall risk and take steps to lower that risk, through lowering cholesterol, weight or blood pressure, for example.

What’s the issue?

Cardiovascular disease accounts for 1 in 4 deaths in the UK each year. A person’s risk of heart disease or stroke depends their weight, cholesterol, smoking status, family history, and other factors. Blood pressure is just one factor.

UK guidelines now recommend that someone’s overall cardiovascular risk, combined with their blood pressure, should guide their treatment. However, in practice, blood pressure readings often drive treatment decisions. Medication is usually started when someone’s blood pressure is above a standard threshold (of 140/90 mm Hg). Lowering blood pressure is still seen as the key way to reduce cardiovascular risk.

Recent research has prompted a re-think about treatment thresholds. It showed that – regardless of someone’s initial blood pressure – their risk of cardiovascular disease goes down with a reduction in their blood pressure of 5mm Hg.

This new study aims to further inform treatment decisions. It compares the use of blood pressure cut-off levels, with overall cardiovascular risk.

What’s new?

Researchers used data on 1 million people, from English GP surgeries, hospitals and death records. People were aged 30 to 79; the average age at the start of the study was 52.

The team assessed each person’s overall risk of having a cardiovascular event (such as a heart attack or stroke). They used a well-known tool called QRISK2. It combines information on age, gender, ethnicity, cholesterol, weight, smoking status, family history of heart disease, and other medical conditions, as well as blood pressure.

Using QRISK2, the researchers classed people as having a low overall risk if their chance of having a cardiovascular event in the next 10 years was 10% or less. They had a high overall risk if that chance was 20% or higher.

Over the next 4 years, almost 52,000 people had a cardiovascular event. The researchers found that these events were more accurately predicted by overall cardiovascular risk, than by blood pressure. Among people with similar blood pressure levels, events increased markedly with rising overall risk score. However, among people with similar overall risk, events increased only slightly with rising blood pressure levels.

The study found, for example, that:

  • people with low overall risk were least likely to have a cardiovascular event, even if their blood pressure was at or above 160mm Hg (in this group, 10 people in every 1,000 had an event each year)
  • people with high overall risk were most likely to have a cardiovascular event, even if their blood pressure was below 140mmHg (in this group, 38 people in every 1,000 had an event each year).

The researchers looked at other conditions that are linked to high blood pressure. Vascular dementia, for example, may be caused by reduced blood flow to the brain. Kidney disease is more likely, and worse, in people with high blood pressure. The team found the same pattern: overall risk predicted these conditions better than blood pressure levels alone.

The results were not affected by sex, age, diabetes status, and whether people were prescribed drugs to lower blood pressure.

Why is this important?

The study confirms that someone’s overall risk of cardiovascular disease has more impact on their chances of having a cardiovascular event than their blood pressure alone. This suggests that overall risk should play an important role in blood pressure management.

Some people not currently prescribed blood pressure medicine might benefit from it. NICE guidelines state that high blood pressure is a reading of 140/90 mmHg or higher. The study suggests that some people with blood pressure lower than this threshold could benefit from treatment if their overall risk is high. The next step is to understand whether the benefits of treating this group of people outweigh any harms.

At a population level, increased focus on overall risk could help prevent more cardiovascular disease, saving money for the NHS.

This research underlines the importance of non-drug approaches to preventing cardiovascular disease. People may wish to consider the other factors that contribute to the risk score. This could include lowering cholesterol or weight, or stopping smoking.

What’s next?

Further research is needed in some groups of people. For example, the study excluded people who already had cardiovascular disease. There was also less data on people younger than 60, and in people with extremely high or low blood pressure. The data implied that people with very high blood pressure (systolic blood pressure more than 180mmHg) had more cardiovascular events, regardless of overall risk.

Most of the people in this study were White. Future research needs to investigate whether the results hold for people of different ethnicities, who may be more likely to have cardiovascular disease.

You may be interested to read

This Alert is based on: Herrett E, Strongman H, Gadd S, and others. The importance of blood pressure thresholds versus predicted cardiovascular risk on subsequent rates of cardiovascular disease: a cohort study in English primary care. Lancet Healthy Longevity 2022;3:1

You can check your own overall cardiovascular score using an online version of QRISK, the tool used in this study

NICE Guideline [NG136] 2019: Hypertension in adults: diagnosis and management.

Funding: This research was supported by NIHR post-doctoral fellowship grants.

Conflicts of Interest: The study authors declare no conflicts of interest.

Disclaimer: NIHR Alerts are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that views expressed in NIHR Alerts are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.


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Comments

Study author

I was surprised about how striking the differences in rates of disease were between categories of predicted overall risk, and how little difference increasing blood pressure made. It made me feel that I would rather keep my predicted risk as low as possible than keep my blood pressure as low as possible – though ideally it would be wise to do both!

Patients should be aware of their overall cardiovascular disease risk, instead of focusing only on their blood pressure levels.  They will benefit from reducing their overall cardiovascular risk, by addressing any one of the risk factors: blood pressure, cholesterol, weight, and so on.

Policymakers should be aware of the potential impact of treating patients with high predicted risk and ‘normal’ blood pressure.

Emily Herrett, Assistant Professor, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine

Stroke Association

“We’ve known for a while that high blood pressure is the biggest risk factor for stroke. This new research says that the combined force of this and other risk factors such as age, ethnicity and alcohol intake might be a better predictor of stroke than blood pressure alone.

Following lots of people over time is a good way to do this sort of study, but it isn’t perfect. This study only followed people for an average of four years, so we don’t know whether the conclusions will be useful in the longer term. Also, stroke can happen at any age and is more common in black and South Asian people. The study didn’t follow anyone under 30 or many people of colour, so clinicians need more information about these groups to give the best possible advice to all their patients.

If the recommendations from this research are taken up, we might start to see more people with high blood pressure but few other risk factors being advised by health professionals to make lifestyle changes before trying medication. However, the advice we would give to people hasn’t changed. To reduce your risk of stroke, it’s important to get your blood pressure checked and managed appropriately if necessary – this might be through lifestyle changes like taking more exercise, or through medication to reduce blood pressure.”

Clare Jonas, Research Communications and Engagement Lead, the Stroke Association

Lived Experience

“I have been taking blood pressure medication and statins for many years and I found this article both reassuring and concerning. I was placed on these medications because my risk scores were high. I am diligent at taking my medication and my blood pressure is well-controlled. This has given me a level of reassurance that may not be wholly justified. I am happy to continue with my medication, but it is a wake-up call for me to see the effect of other factors in the predicted risk score, which I have become a little complacent about.”

Peter Green, Public Contributor, Sunderland 

 

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