As we age our carotid artery which leads from the brain to the heart gradually becomes blocked with fatty deposits of plaques in a process known as atherosclerosis.
The narrowing and hardening of the artery restricting the blood flow and oxygen supply to the brain and increasing the risk of blood clots that could potentially block the flow of blood to the heart or brain.
The new study found the effects of having atrial fibrillation and carotid artery disease combines and the resulting restriction on blood flow to the brain increases dementia risk.
Clinical Researcher Dr Victoria Jacobs at the Intermountain Medical Centre Heart Institute in Salt Lake City said: “Our team of researchers has been studying links between atrial fibrillation and dementia.
“This new data stresses the continued need for physicians to monitor and screen patients for both carotid artery disease and atrial fibrillation, especially patients who have risk factors of either disease.”
Carotid artery disease is a major cause of stroke, accounting for about a fifth of all cases in the UK.
Atrial fibrillation is the most common heart rhythm disturbance, affecting around one million Britons.
Generally it affects the over 65s and is more common in patients with high blood pressure or atherosclerosis or a heart valve problem.
The abnormal heart rhythm causes blood to pool and clot in the heart and when those blood clots break free, they can cause a stroke.
Previous research had found the abnormal heart rhythms of atrial fibrillation produce inconsistent blood flow to the brain, which contributes to the onset of dementia or a decrease in cognitive function.
Risk factors are similar for atrial fibrillation and carotid artery disease and include age, weight, hypertension, high cholesterol, and diabetes. Smoking can also increase risk.
Yet those with carotid artery disease generally does not show any symptoms until a stroke hits.
The study examined 6,786 patients with carotid artery disease with no history of dementia and compared those in the group diagnosed with atrial fibrillation to those with no diagnosis of atrial fibrillation.
The average age of the patients was 71.6 years old and 55.6 per cent of them were male. Twenty one per cent had atrial fibrillation.
Dr Jacobs concluded: “Atrial fibrillation and carotid artery disease are treatable, and addressing those diseases early on can help reduce the risk of developing dementia.
“Physicians should be discussing the treatment options with patients who are at risk to help educate them about what they can do to live the healthiest life possible.
“Patients should be engaged in their own healthcare, knowledgeable about their risks, and active in maintaining healthy lifestyles.
“Neither disease should be accepted passively, because both are treatable, and treatment is especially important given the benefit of helping to prevent or postpone dementia.”
Further research will analyse the data to compare it among different groups to see what patterns may exist in identifying a patient’s risk of developing dementia.
The findings were presented at the Heart Rhythm Society’s 39th annual Scientific Sessions in Boston.