Specific regions of the brain that are damaged by high blood pressure and may contribute to the development of dementia have been identified by researchers for the first time.
High blood pressure is known to be involved in causing dementia and damage to brain function. The study, published in the European Heart Journal, details how this happens, providing a step forward in understanding the link between high blood pressure and dementia.
The study drew its conclusions after gathering information from a combination of magnetic resonance imaging (MRI) scans of brains, genetic analyses, and observational data from thousands of patients to look at the effect of high blood pressure on cognitive function. The researchers then checked their findings in a separate, large group of patients in Italy.
Lead researcher, Tomasz Guzik, professor of cardiovascular medicine at the University of Edinburgh and Jagiellonian University Medical College in Krakow Poland, said: "We have identified specific parts of the brain that are affected by increases in blood pressure, including areas called the putamen and specific white matter regions.
"We thought these areas might be where high blood pressure affects cognitive function, such as memory loss, thinking skills, and dementia. When we checked our findings by studying a group of patients in Italy who had high blood pressure, we found that the parts of the brain we had identified were indeed affected."
He hopes the findings could lead the way to the development of new ways to treat cognitive impairment in people with high blood pressure.
"Studying the genes and proteins in these brain structures could help us understand how high blood pressure affects the brain and causes cognitive problems. Moreover, by looking at these specific regions of the brain, we may be able to predict who will develop memory loss and dementia faster in the context of high blood pressure. This could help with precision medicine, so that we can target more intensive therapies to prevent the development of cognitive impairment in patients most at risk," added Prof Guzik.
Nine Areas of the Brain Affected
The international team of researchers was co-funded by the European Research Council, the British Heart Foundation, and the Italian Ministry of Health. They looked at brain MRI imaging data from over 30,000 people taking part in the UK Biobank study.
A technique called Mendelian randomisation was used, to see if high blood pressure was actually the cause of changes to specific parts of the brain rather than just being associated with these changes.
"Mendelian randomisation is a way of using genetic information to understand how one thing affects another," explained Prof Guzik. "In our study, if a gene that causes high blood pressure is also linked to certain brain structures and their function, then it suggests that high blood pressure might really be causing brain dysfunction at that location, leading to problems with memory, thinking, and dementia.
"The study identified changes to nine parts of the brain which were related to high blood pressure and worse cognitive function," he summarised.
The regions included the putamen, which is responsible for regulating movement and influencing various types of learning. Other areas affected were the anterior thalamic radiation, anterior corona radiata, and anterior limb of the internal capsule, which are regions of white matter that connect and enable signalling between different parts of the brain. The anterior thalamic radiation is involved in executive functions, such as the planning of simple and complex daily tasks, while the other two regions are involved in decision-making and the management of emotions.
The changes to these areas included decreases in brain volume and the amount of surface area on the brain cortex, changes to connections between different parts of the brain, and changes in measures of brain activity.
Hopes For New Treatment
Co-author of the study, Professor Joanna Wardlaw, head of neuroimaging sciences at the University of Edinburgh, said: "It has been known for a long time that high blood pressure is a risk factor for cognitive decline, but how high blood pressure damages the brain was not clear. This study shows that specific brain regions are at particularly high risk of blood pressure damage, which may help to identify people at risk of cognitive decline in the earliest stages, and potentially to target therapies more effectively in future. "
Professor James Leiper, associate medical director at the British Heart Foundation, which funded the research, told Medscape News UK: "By identifying specific areas of the brain which are damaged by high blood pressure, researchers have taken a significant step forward in our understanding of the concerning link between high blood pressure and cognitive decline.
"The nine brain areas identified can become nine new points of focus for further research on how high blood pressure causes damage.
"Cognitive decline can be very debilitating and scary for those patients suffering from it. By continuing to improve our understanding of the changes in these brain areas effect cognitive function, we could potentially find new ways of stopping many people with high blood pressure from having to experience it."
Possibility of Earlier Detection of Damage to the Brain
Dr Timothy Rittman, senior research fellow at Alzheimer's Research UK, said: "High blood pressure is very common and, if untreated, can increase the risk of certain forms of dementia in later life.
"This study starts to unravel the reasons why this is by using sophisticated statistical methods to draw a link between high blood pressure, problems with memory and thinking, and, for the first time, shrinkage in specific parts of the brain.
"It could lead to new ways to measure the damage that blood pressure has on the brain, which could have a very big impact in helping reduce dementia risk.
"That's because, if the early signs of damage to the brain could be spotted early, we can potentially slow this down with better blood pressure monitoring and treatment."
Limitations of the study include that participants from the UK Biobank are mainly White and middle-aged, so it might not be possible to extrapolate the findings to other groups.
This study was funded by the European Research Council, British Heart Foundation, and as part of the British Heart Foundation Centre for Research Excellence at the University of Edinburgh, and the Italian Ministry of Health.