Factors that influence the health of our blood vessels, such as smoking, high blood and pulse pressures, obesity, and diabetes, are linked to less healthy brains, according to research from the U.K.
The study examined the associations between seven vascular risk factors and differences in the structures of parts of the brain. The strongest links were with areas of the brain known to be responsible for our more complex thinking skills, and which deteriorate during the development of Alzheimer’s disease and dementia.
How was the Study Conducted?
The researchers, led by Dr. Simon Cox, a senior research associate at the Center for Cognitive Aging and Cognitive Epidemiology at the University of Edinburgh (UK), examined MRI scans of the brains of 9,772 people, aged between 44 and 79, who were enrolled in the UK Biobank study – one of the largest groups of people from the general population to have data available on brain imaging as well as general health and medical information.
All had been scanned by a single scanner in Cheadle, Manchester, and most of the participants were from the north-west of England. This is the world’s largest single-scanner study of multiple vascular risk factors and structural brain imaging.
The researchers looked for associations between brain structure and one or more vascular risk factors, which included smoking, high blood pressure, high pulse pressure, diabetes, high cholesterol levels, and obesity as measured by body mass index (BMI) and waist-hip ratio.
These have all been linked to complications with the blood supply to the brain, potentially leading to reduced blood flow and the abnormal changes seen in Alzheimer’s disease.
What were the findings?
They found that, with the exception of high cholesterol levels, all of the other vascular risk factors were linked to greater brain shrinkage, less grey matter (tissue found mainly on the surface of the brain) and less healthy white matter (tissue in deeper parts of the brain). The more vascular risk factors a person had, the poorer was their brain health.
“The large UK Biobank sample allowed us to take a comprehensive look at how each factor was related to many aspects of brain structure,” Cox said. “We found that higher vascular risk is linked to worse brain structure, even in adults who were otherwise healthy.”
Cox said these links were just as strong for people in middle-age as they were for those in later life, and the addition of each risk factor increased the size of the association with worse brain health.
“Importantly, the associations between risk factors and brain health and structure were not evenly spread across the whole brain,” Cox explains, “Rather, the areas affected were mainly those known to be linked to our more complex thinking skills and to those areas that show changes in dementia and ‘typical’ Alzheimer’s disease.”
He says although the differences in brain structure were generally quite small, these are only a few possible factors of a potentially huge number of things that might affect brain aging.”
Smoking, high blood pressure, and diabetes were the three vascular risk factors that showed the most consistent associations across all types of brain tissue types measured. High cholesterol levels were not associated with any differences in the MRI scans.
To quantify the size of the differences they observed, Cox explained the researchers compared people with the most vascular risk factors with those who had none, matching them for head size, age, and sex.
“We found that, on average, those with the highest vascular risk had around 18 ml, or nearly 3%, less volume of grey matter, and one-and-a-half times the damage to their white matter – the brain’s connective tissue – compared to people who had the lowest risk; 18 ml is slightly more than a large tablespoon-full, or a bit less than a small, travel-sized toothpaste tube,” Cox explains.
He said that the findings showed the potential of making lifestyle changes to improve brain and cognitive aging.
“Lifestyle factors are much easier to change than things like your genetic code – both of which seem to affect susceptibility to worsening brain and cognitive aging.
Because we found the associations were just as strong in mid-life as they were in later life, it suggests that addressing these factors early might mitigate future negative effects.
These findings, the researchers believe might provide additional motivation to improve vascular health beyond respiratory and cardiovascular benefits.
What were the study limitations?
Limitations of the study include the fact that it does not include people over the age of 79 and that U.K. Biobank participants tend to live in less deprived areas, which may restrict how the findings can be generalized to other populations.
As the researchers were measuring brain structures only and were not carrying out functional brain imaging or tests of thinking skills, they cannot show in this study how the changes in brain structure might impact cognitive function, but other studies have shown the relationship between increased numbers of vascular risk factors and worse or declining thinking skills, and dementia.
What Steps Are Ahead?
Now the researchers plan to measure the links between vascular risk factors and thinking skills in the U.K. Biobank participants and in other groups too.
In addition, they are following older people and carrying out multiple scans and tests of thinking skills. They hope this will tell them more about the role that vascular risk factors play in the decline of different types of thinking skills and which areas of the brain are implicated.
They also hope that the findings will motivate future work to understand the biological mechanisms through which different sources of vascular risk might be related to different brain areas and tissues.
The research has been published in the European Heart Journal.
European Society of Cardiology.
Smoking, high blood pressure, diabetes, and obesity each linked to unhealthy brains. (2019, March 10). Retrieved: https://www.eurekalert.org/pub_releases/2019-03/esoc-shb030719.php