People who have high blood pressure may be twice as likely to die from COVID-19 than those without the medical condition, according to research. Scientists have said the risk is even greater among patients who are not taking medication to control hypertension.

The risk of death among those with high blood pressure was found to vary depending on the antihypertensive treatment the patients were receiving. However, the researchers said this result “should be interpreted cautiously”, adding that “patients should not discontinue or change their normal, antihypertensive treatment” unless advised by their doctor.

The findings, reported in the European Heart Journal, are based on data from nearly 3,000 hospital patients in Wuhan, China.

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Professor Fei Li, from Xijing Hospital in China and one of the study authors, said: “It is important that patients with high blood pressure realise that they are at increased risk of dying from COVID-19.

“They should take good care of themselves during this pandemic and they need more attention if they are infected with the coronavirus.”

A team of scientists, which also included researchers from the National University of Ireland Galway, looked at data from 2,866 patients admitted to hospital with COVID-19 between 5 and 15 February. Of these patients, 850 (29.5 per cent) had a medical history of hypertension.

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The team found 34 out of 850 patients (4 per cent) with hypertension died after becoming infected with coronavirus, compared with 22 out of 2,027 patients without the condition (1.1 per cent).

We suggest that patients should not discontinue or change their usual antihypertensive treatment unless instructed by a physician
Professor Fei Li

After adjustment for factors such as age, sex and other medical conditions, the researchers said those with high blood pressure had more than a two-fold increased risk of dying from COVID-19.

Among the patients who were not taking medication for hypertension, 11 out 140 (7.9 per cent) died from coronavirus, compared with 23 out of 710 (3.2 per cent) of those consuming the medicines.

The researchers then pooled data from three other studies involving nearly 2,300 patients to investigate the role played by RAAS inhibitors, a class of drugs commonly used to treat blood pressure, such as ACE inhibitors and ARBs, in COVID-19 death risk.

They found the risk of death to be lower among the patients who took RAAS inhibitors compared with those treated with other drugs such as beta blockers, calcium channel blockers (CCBs) or diuretics.

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Prof Li said: “In contrast to our initial hypothesis, we found that RAAS inhibitors, such as ACE inhibitors or angiotensin receptor blockers, were not linked to an increased risk of dying from COVID-19 and, in fact, may be protective.

“Therefore, we suggest that patients should not discontinue or change their usual antihypertensive treatment unless instructed by a physician.”

A randomised clinical trial testing the effects of blood pressure medication on COVID-19 patients is set to run at the National University of Ireland Galway as part of the next steps in the research.

What is the R number, and why is it relevant to coronavirus?

The reproduction number – often called the R value or R number – is a measure of a disease’s ability to spread. It tells us how many people a single infected person will pass on the disease to.

The R number for COVID-19 that’s being quoted in the media and government briefings is what’s known as the ‘effective’ reproduction number. This value can go up and down.

We can reduce R by making it harder for the disease to spread, by implementing measures such as social distancing, closing restaurants and non-essential shops, and encouraging people to stay at home.

Every disease also has what’s called a ‘basic’ reproduction number, R0, which is the fixed value of R if no measures are put in place. For example, measles is highly contagious, with a R0 as high as 18, while COVID-19 has a R0 of around three.

So if COVID-19 was allowed to spread through the population, an infected person would, on average, give the disease to three other people.

But if all these people are practising physical distancing, then the virus can’t spread so easily and the effective R value goes down.

The crucial thing is to keep R below 1. If we can do this, then the number of new cases dwindles and the outbreak will eventually come to a halt.

Conversely, if R rises above 1, then we run the risk of rapidly escalating case numbers that would require stronger measures to keep the virus under control.

Because of this, R is used by governments to assess how we are doing in our efforts to stop the spread of COVID-19, and to adjust our actions, if needed.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.