Early brain dysfunction is caused by heart disease, which can increase the amount of a critical Alzheimer's protein.

According to scientists, heart problems can trigger early brain malfunction that can lead to dementia and treble the quantity of an Alzheimer's protein in the brain.

Heart disease causes a failure of a fundamental brain function that links brain activity and blood flow, meaning the brain receives less blood for the same level of activity, according to new research published in eLife.

This occurs in heart disease patients prior to the accumulation of fat in the brain's blood arteries (atherosclerosis), and it is a precursor to dementia. It was previously unknown how some forms of vascular dementia can develop years before atherosclerosis develops in the brain.

The researchers also observed that combining heart problems with a genetic susceptibility to Alzheimer's disease triples the quantity of beta-amyloid, a protein that builds up and promotes Alzheimer's, and raises the levels of an inflammatory gene (IL1) in the brain.

"Alzheimer's Disease is the most common form of dementia worldwide, and heart disease is a major risk factor for both Alzheimer's and dementia," said Dr Osman Shabir, main author of the study from the University of Sheffield's Neuroscience and Healthy Lifespan Institutes. The new findings will help us learn more about the links between heart disease and dementia.

"We've discovered that heart illness in middle age triggers the breakdown of neurovascular coupling, a critical brain function that regulates the amount of blood delivered to our neurons. This breakdown means the brain isn't getting enough oxygen when it's needed, which can lead to dementia over time."

The British Heart Foundation has recently offered the team a three-year funding to investigate the use of an arthritis treatment that targets IL1 to determine if it might correct or minimise the brain dysfunction caused by heart disease.

The researchers also discovered that brain traumas can exacerbate brain blood flow regulation, corroborating previous findings that patients' symptoms often deteriorate after injuries or falls.

Reference:

Osman Shabir, Ben Pendry, Llywelyn Lee, Beth Eyre, Paul S Sharp, Monica A Rebollar, David Drew, Clare Howarth, Paul R Heath, Stephen B Wharton, Sheila E Francis, Jason Berwick. Assessment of neurovascular coupling and cortical spreading depression in mixed mouse models of atherosclerosis and Alzheimer’s disease. eLife, 2022; 11 DOI: 10.7554/eLife.68242