Early on, heart disease can lead directly to brain dysfunction that can lead to dementia and triple the amount of an Alzheimer’s protein in the brain, scientists say.
The new study, published in eLife, has found that heart disease causes a breakdown in a key brain function that links brain activity and blood flow, meaning the brain gets less blood for the same amount of activity.
This occurs in patients with heart disease before the accumulation of fat in the blood vessels of the brain (atherosclerosis) and is a prelude to dementia. Until now, it has been unclear how some forms of vascular dementia can appear years before atherosclerosis develops in the brain.
The researchers also discovered that the combination of heart disease and a genetic predisposition to Alzheimer’s disease tripled the amount of beta-amyloid, a protein that builds and triggers Alzheimer’s, and increases levels of an inflammatory gene (IL1) in the brain.
dr Osman Shabir, lead author of the study from the University of Sheffield’s Neuroscience and Healthy Lifespan Institutes, said: “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.” The new findings are key to our understanding of the links between heart disease and dementia.
“We have discovered that midlife heart disease leads to the breakdown of neurovascular coupling, an important mechanism in our brain that controls the amount of blood supplied to our neurons. This breakdown means the brain isn’t getting enough oxygen when it needs it and not in time, which can lead to dementia.”
The team has since won a three-year grant from the British Heart Foundation to study the use of an arthritis drug that targets IL1 to see if it could reverse or reduce brain dysfunction caused by heart disease.
The team also found that brain injuries can also worsen the regulation of cerebral blood flow, supporting observations that patients’ symptoms often worsen after injuries or falls.