Lifestyle choices, diseases, linked to unhealthy brain

Lifestyle factors and diseases that influence the health of blood vessels, such as smoking, high blood pressure, obesity, and diabetes, may be linked to less healthy brains, according to new research published earlier today in the European Heart Journal.

The study, led by researchers at the Centre for Cognitive Ageing and Cognitive Epidemiology at the University of Edinburgh in Scotland, United Kingdom, 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 more complex thinking skills, and which deteriorate during the development of Alzheimer's disease and dementia.

The researchers, led by Simon Cox, MA, MSc, PhD, a senior research associate at the University of Edinburgh, examined MRI scans of the brains of 9,772 people, aged between 44 and 79, who were enrolled in the U.K. 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.

The team 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.

The study 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 or tissue found mainly on the surface of the brain, and less healthy white matter or tissue in deeper parts of the brain. The more vascular risk factors a person had, the poorer was their brain health, according to the study, which was announced formally by the university this morning.

Further, the team compared people with the most vascular risk factors with those who had none, matching them for head size, age, and sex. They found that, on average, those with the highest vascular risk had nearly 3 percent 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.

The associations between risk factors and brain health and structure were not evenly spread across the whole brain, said Cox. The areas affected were mainly those known to be linked to more complex thinking skills and to those areas that show changes in dementia and 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 aging, he said.

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, Cox said. The findings showed the potential of making lifestyle changes to improve brain and cognitive aging, he said.

"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 aging,” said Cox. “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."

The results are limited, researchers say, because it does not include people over the age of 79, and U.K. Biobank participants tend to live in less deprived areas. Further, the study measured brain structures only, and did not include functional brain imaging or tests of thinking skills.

Researchers say they plan to measure the links between vascular risk factors and thinking skills in the study participants, as well as a broader group. 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.