Human brain isolated on dark background. 3D render

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 published in the European Heart
Journal today (11 March).

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.

The researchers, led by Dr Simon Cox, a senior research
associate at the Centre for Cognitive Ageing and Cognitive Epidemiology at the
University of Edinburgh (UK), examined MRI scans of the brains of 9772 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

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.

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 and less healthy white matter. The more vascular
risk factors a person had, the poorer was their brain health.

Dr Cox said: “The large UK Biobank sample allowed us to take
a comprehensive look at how each factor was related to many aspects of brain
structure. We found that higher vascular risk is linked to worse brain
structure, even in adults who were otherwise healthy. 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;
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. 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 ageing.”

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, Dr
Cox explained: “We 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 18ml, or nearly 3%,
less volume of grey matter, and one-and-a-half times the damage to their white
matter compared to people who had the lowest risk; 18ml is slightly more than a
large tablespoon-full, or a bit less than a small, travel-sized toothpaste

He said that the findings showed the potential of making
lifestyle changes to improve brain and cognitive ageing.

“Lifestyle factors are much easier to change than things
like your genetic code – both of which seem to affect susceptibility to worse
brain and cognitive ageing. 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
might provide an additional motivation to improve vascular health beyond
respiratory and cardiovascular benefits.”


Reference: Cox
SR, et al. Associations between vascular risk factors and brain MRI indices in
UK Biobank. European Heart Journal.
Published 11 March 2019.