The conditions appeared to cause structural changes that harmed memory and thinking.
High blood pressure and diabetes bring about brain changes that impair thinking and memory, research suggests.
Doctors examined brain scans and medical data from 22,000 volunteers enrolled in the UK Biobank project and found significant structural changes in the grey and white matter among those with diabetes and high blood pressure.
The same individuals tended to fare worse on cognitive tests that measured their thinking speed and short-term memory, raising the possibility that the medical conditions were driving mental decline.
“Remarkably, the findings show that it is possible to detect the negative effect of cardiovascular risk factors, such as raised blood pressure and diabetes, on cognitive function and brain structure in otherwise healthy people,” said Masud Husain, a professor of neurology and cognitive neuroscience at the Nuffield Department of Clinical Neurosciences at Oxford University.
“The major implication is that these risk factors don’t just have an influence on what happens later in life – the risk of developing dementia – they also have an impact on the brain and current levels of cognitive function in mid-life,” he added.
The study found that for people on treatment, systolic blood pressure above 140mm, measured when the heart is contracting, was associated with lower cognitive performance. “For blood pressure, every millimetre of pressure in your arteries counts, even in people who aren’t on any treatment. The higher the pressure, the worse it is,” Husain said.
Writing in the journal Nature Communications, the researchers describe how the link was strongest in people aged 44 to 69 years, but had less of an impact in the over-70s. The effects on cognitive performance are small, with mental processing slowing down by fractions of a second, but given that it takes only a millisecond for information to cross a synapse in the brain, even small declines can affect cognitive function.
he volunteers’ short-term memory was tested with an online pair-matching game, while their mental processing speed was recorded by measuring reaction times. Both were performed on the same day as the brain scans.
Previous studies have shown that high blood pressure and diabetes in mid-life can raise the risk of dementia later on, but the latest findings suggest the conditions can affect the brain before more severe cognitive decline develops.
In the UK, one in 10 people over 40 live with type 2 diabetes, while one in four have high blood pressure, a condition described as a “silent killer” because it increases the risk of heart attack and stroke but rarely causes symptoms beforehand.
Husain believes the findings could have important implications for public health. Doctors do not often treat mildly raised blood pressure, but the research suggests this might be a missed opportunity.
“We can detect that even small increases in blood pressure have an impact on the brain right now. It is not surprising that if this is allowed to continue untreated for decades, it might have a cumulative impact on brain structure and function, eventually making it vulnerable to dementia,” he said.