Stroke is the fourth biggest killer in the UK. High blood pressure (BP) is one of the key modifiable risk factors for stroke (it’s a risk factor that can be changed). High BP is thought to contribute to around half of strokes in England, Wales and Northern Ireland.
BP is usually measured on the upper arm using an inflatable cuff. However, sometimes this isn’t possible – this could be due to arm problems caused by stroke or missing limbs. If BP can’t be measured in the arm then it can be measured in the leg instead.
However, BP readings taken in the leg are higher than those taken in the arms, and we currently don’t know how leg and arm readings are related. This is a problem because current clinical guidelines for treating high BP are based on readings taken in the arm. This means that people who can’t have their BP taken in their arm are at risk of not being properly diagnosed with, and treated for, high BP, which could mean they are at increased risk of having a stroke.
This research project will investigate the relationship between BP in the arm and leg, and the link to stroke. The researchers will create a model that can be used to predict arm BP readings based on leg BP and patient characteristics, such as age, medical history and body mass index.
This study will use data from ‘The Inter-arm blood pressure difference individual patient data collaborations’ (INTERPRESS-IPD) dataset. This contains information collected from a number of individual research studies that have been brought together to form one large set of data. In total the INTERPRESS-IPD dataset contains information from 34,000 people from around the world.
The research team will analyse the data in the INTERPRESS-IPD dataset to answer the following questions:
1. What is the relationship between arm and leg BP?
2. Can a person’s leg BP and other characteristics (such as age) predict their arm BP?
3. How do leg BP readings (compared with arm BP) predict strokes and death?
4. Can someone’s leg BP, and the relationship between their arm and leg BP, predict their risk of stroke?
Using data that has been collected in previous studies means that the research team will be able to answer these questions much more quickly, and for a lot less money, than if they had to collect the data of another 34,000 people.
Current clinical guidelines that outline what is considered to be high BP (i.e. when treatment to lower BP should be started) are based on readings taken in the arm. Knowing more about how BP readings in the leg relate to those in the arm will allow doctors to confidently diagnose patients who have high BP and would benefit from treatment, according to guidelines. Ultimately, this would hopefully reduce the risk of stroke in people who can’t have their BP taken in their arm.