Blood pressure measurements should be taken from BOTH arms because a big variation between the two readings is linked to a greater risk of heart attack, scientists claim
- Greater difference in blood pressure between arms linked to larger health risk
- Bilateral blood pressure guidelines on what constitutes a risk should be lowered
- Hypertension (high blood pressure) is a key risk factor of cardiovascular disease
Taking blood pressure measurements from both arms could help save lives, researchers have said.
UK experts found ‘robust evidence’ that a difference in blood pressure between both arms is linked to a greater risk of heart attack, stroke and death.
Their findings are based on data gathered from 24 global studies of nearly 54,000 people, spanning Europe, the US, Africa and Asia.
International blood pressure guidelines advise health professionals to measure blood pressure in both arms when assessing cardiovascular risk, but this is ‘widely ignored’, the experts claim.
Current UK and European guidelines on what constitutes a risk in terms of blood pressure differences between the arms – known as bilateral blood pressure – should be lowered from 15 to 10 millimetres of mercury (mmHg), they say.
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Robust evidence from a large international study confirms that a difference in blood pressure readings between arms is linked to greater risk of heart attack, stroke and death
The new study provides a new upper limit of ‘normal’ for an inter-arm difference in blood pressure, which is significantly lower than the current guidance.
This could alter international hypertension guidelines, meaning more at-risk patients could be identified and receive potentially life-saving treatment.
‘Checking one arm then the other with a routinely used blood pressure monitor is cheap and can be carried out in any healthcare setting, without the need for additional or expensive equipment,’ said lead study author Dr Chris Clark at the University of Exeter Medical School.
‘Whilst international guidelines currently recommend that this is done, it only happens around half of the time at best, usually due to time constraints.
‘Our research shows that the little extra time it takes to measure both arms could ultimately save lives.’
The team did not set out to establish causality – whether high bilateral blood pressure causes health problems blood.
‘We are not saying that an inter-arm difference causes strokes or heart attacks,’ Dr Clark told MailOnline.
‘Our belief is that a difference between blood pressure between arms represents underlying differences in the health of the arteries (the brachial arteries) that we are using to measure the arm blood pressure.’
High blood pressure – also known as hypertension – is one of the main risk factors of cardiovascular diseases, such as coronary artery disease and heart attacks.
Around a third of adults in the UK have high blood pressure, although many will not realise it, according to the NHS.
The British Heart Foundation put this estimate at just over a quarter – around 14.4 million UK adults.
HOW IS BLOOD PRESSURE MEASURED?
A millimetre of mercury is a unit used to measure blood pressure and other pressures.
Millimetre of mercury, or mmHg, is a unit of pressure equal to the pressure exerted by a column of mercury 1 millimetre high at 0°C and under the acceleration of gravity.
A healthy diastolic blood pressure in children is around 50-80 mmHg.
While health experts have long known that a difference in blood pressure between the two arms is linked to poorer health outcomes, their study helps to understand this association in greater detail.
‘It tells us that the higher the difference in blood pressure between arms, the greater the cardiovascular risk, so it really is critical to measure both arms to establish which patients may be at significantly increased risk,’ Dr Clark said.
‘Patients who require a blood pressure check should now expect that it’s checked in both arms, at least once.’
Blood pressure is a measure of the force that the heart uses to pump blood around the body, and it rises and falls in a cycle with each pulse.
It is measured in units of millimetres of mercury (mmHg), and the reading is always given as two numbers – systolic pressure (the pressure when the heart pushes blood out) and diastolic pressure (the pressure when the heart rests between beats).
The systolic reading represents the maximum blood pressure and the diastolic reading is the minimum blood pressure.
A high systolic blood pressure in one arm alone indicates hypertension.
Pictured, the different categories of blood pressure, as detailed by the American Heart Association
Meanwhile, a significant difference between the systolic blood pressure measurements in the two arms could also be indicative of a narrowing, or a stiffening, of the arteries, which can affect blood flow.
These arterial changes are recognised as a further risk marker for subsequent heart attack, stroke or early death, and should be investigated for treatment, according to the team.
‘Evidence from previous studies by our group and others suggests that stiffening of the arteries may be the underlying process here,’ Dr Clark told MailOnline.
‘Stiffening occurs early in the course of arterial disease and may not be symmetrical in the earliest stages.
‘The measured systolic blood pressure in the arm will be affected (augmented) if the artery is becoming stiff, due to changes in the speed of pulse waves along the artery, increasing with stiffening.’
Arterial changes tend to occur at multiple sites, so it’s possible that the differences in the health of the brachial arteries is ‘a clue’ to the state of other arteries, such as cerebral or coronary, Dr Clark said.
Both UK and European guidelines recognise a systolic difference of 15 mmHg or more between the two arms as the threshold to be associated with additional cardiovascular risk.
Led by the University of Exeter, the scientists searched for studies recording bilateral blood pressure and outcomes and created a single international dataset, called INTERPRESS-IPD Collaboration.
Data was merged from 24 studies, with a total 53,827 people looked at
The data spanned adults from Europe, the US, Africa and Asia for whom blood pressure readings for both arms were available.
The team analysed data on inter-arm blood pressure difference, and tracked the number of deaths, heart attacks and strokes that occurred in the cohort over 10 years.
The researchers found that a lower threshold of 10 mmHg was clearly indicative of additional risk, which ‘would mean that far more people should be considered for treatment if such a difference between arms is present’.
Blood pressure is a measure of the force that the heart uses to pump blood around the body, and it rises and falls in a cycle with each pulse
‘We believe that a 10 mmHg difference can now reasonably be regarded as an upper limit of normal for systolic inter-arm blood pressure, when both arms are measured in sequence during routine clinical appointments,’ said study co-author Professor Victor Aboyans at the Dupuytren University Hospital in Limoges, France.
‘This information should be incorporated into future guidelines and clinical practice in assessing cardiovascular risk.
‘It would mean many more people were considered for treatment that could reduce their risk of heart attack, stroke and death.’
An inter-arm difference of greater than 10 mmHg occurs in 11 per cent of people with high blood pressure (hypertension) – itself a known health risk – and in four per cent of the general population.
The study has been published in Hypertension.
Children exposed to high air pollution levels in the womb and early life ‘more likely to suffer from high blood pressure’
Babies exposed to air pollution when they’re still in the womb may end up with higher blood pressure as a child, a 2020 study suggests.
Researchers studied effects of exposure to environmental factors such as pollution, noise and a densely-built environment on babies both before and after birth.
The experts, from the Barcelona Institute for Global Health, looked at mothers and babies based in six European cities, including Bradford in the UK.
They found a link between high blood pressure as a child and exposure to high levels of air pollution, as well as building density, noise, low proximity to green spaces and low socio-economic status.
Hypertension – high blood pressure – is one of the main risk factors of cardiovascular diseases, such as coronary artery disease and heart attacks.
The experts say urban planners need to take into account the effects of such factors to save children from cardiovascular diseases by the time they reach adulthood.
‘Our results show that, from conception onwards, the urban environment can affect blood pressure in preschool children,’ said study author Charline Warembourg at Barcelona Institute for Global Health.
‘This means that a commitment to urban design and transport planning designed to reduce damaging environmental exposures has the potential to reduce the risk of cardiovascular disease in adulthood.’
Read more: Early exposure to air pollution linked with higher blood pressure
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