For some time, scientists have known that high blood pressure is somehow involved in cognitive decline leading to dementia. Backing the evidence are several studies that saw blood pressure and related diabetes medicines help slow the loss of brain function.
But for the first time, scientists have been able to identify nine specific areas of the brain where damage from high blood pressure (HBP) may contribute to cognitive decline, opening the door to treatment before the onset of neurodegeneration.
"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,” said co-author of the study Joanna Wardlaw, head of neuroimaging sciences at the University of Edinburgh. “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."
The discovery came about only after an international team of researchers looked at the MRI images of more than 30,000 participants in the UK Biobank study, as well as genetic analyses from several genome-wide association studies, and observational studies of patients and Mendelian randomization was applied to see if HBP caused changes to these specific brain regions rather than just sharing the geography.
“[Mendelian randomization] works by using a person's genetic information to see if there is a relationship between genes predisposing to higher blood pressure and outcomes,” said research lead Tomasz Guzik, professor of cardiovascular medicine at the University of Edinburgh and Jagiellonian University Medical College, Krakow. "If there is a relationship, then it is more likely that the high blood pressure is causing the outcome. This is because genes are randomly passed down from parents, so they are not influenced by other factors that could confuse the results.”
The regions of the brain the team identified include the putamen, which is involved in regulating movement and helping with learning, the anterior thalamic radiation, which deals with executive functions like planning daily tasks, plus the anterior corona radiata and the anterior limb of the internal capsule, which concern decision making and emotional management.
In these areas, the scientists found decreased brain volume and surface area on the brain cortex, changes to connections between regions and altered brain activity measurements.
"By using this combination of imaging, genetic and observational approaches, 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,” Guzik said. “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.”
Some 116 million adults in the US – nearly half the adult population, have HBP, or hypertension, but only about a quarter have the condition under control. Its impacts on stroke, heart disease and heart failure are well known, but until now the links with brain decline haven’t been as clear.
"We hope that our findings may help us to develop new ways to treat cognitive impairment in people with high blood pressure,” said Guzik. “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."
The study was published in the European Heart Journal.
Source: European Society of Cardiology