Tromsø researchers have found the connection between atrial fibrillation and dementia

Atrial fibrillation, which can cause an irregular pulse, dizziness, difficulty breathing and anxiety, occurs in as many of 20 per cent of people in their 80s. The occurrence in people in their 50s is just one per cent.

It’s most common in people who exercise the least, and who are obese, or have high blood pressure, other types of heart disease or diabetes.

But oddly enough, it can also affect elite athletes. A year ago, the Norwegian Olympic biathlete Ole Einar Bjørndalen told NRK, the Norwegian Broadcasting Association, that he had had heart fibrillation for ten years. Marit Bjørgen, who is the most successful female cross-country skier in the world, has also had this problem.

A study done by researchers at UiT- the Arctic University of Norway has shown that moderate physical activity protects against atrial fibrillation. People who are couch potatoes have 20 per cent more atrial fibrillation than average. People who train the most have the highest risk of this type of heart arrhythmia.

What happens with the brain?

Maja-Lisa Løchen at UiT The Arctic University of Norway has long been interested in atrial fibrillation and what effect it might have on the brain. How are memory and concentration affected when the heart provides an irregular supply of blood to the brain?

And she and her colleagues have an excellent resource to find answers to exactly these questions. The Tromsø Study is one of Norway’s most comprehensive population studies and has been underway for the last 45 years.

As part of the study, researchers have created a register based on hospital journals that show occurrences of atrial fibrillation in Tromsø since 1986. They have tested cognitive function in study participants a number of times.

Løchen’s PhD candidate, Sweta Tiwari, has used these data to look at people who had atrial fibrillation but who hadn’t had a stroke. The average age of the group she studied was 65. She compared this group to people who did not have atrial fibrillation.

Her results were worrying for people who have atrial fibrillation, but a breakthrough for researchers. For the first time, they were able to show that there was a significant difference in changes in cognitive function between people who had atrial fibrillation and those who didn’t.

40 per cent poorer result

The researchers used three standard cognitive tests in the study. The first was a pure memory test, the second was a test of numbers and signs, and third was a tempo test, called the tapping test.

This last measured how many times a study participant could tap a letter on a keyboard during a specific period.

On the first two tests, the researchers saw no difference between those who had atrial fibrillation and those who did not.

But they saw a big difference in the tapping test. Individuals with atrial fibrillation had a 40 per cent greater decrease in cognitive function over seven years than those who did not have the heart arrhythmia.

The brain gets too little oxygen

Atrial fibrillation can be dangerous in several ways.

When the heart does not beat as regularly as it should, but fibrillates, the blood moves irregularly into the body. When blood accumulates, a blood clot may form inside the atrial chamber. The blood clot can loosen and pass through the main artery.

The worst thing that can happen is that the blood clot goes to the brain. Fifteen to 20 per cent of all strokes are due to atrial fibrillation.

Researchers explain the connection between fibrillation and dementia in two ways: There is an uneven oxygen supply to the brain during fibrillation. In addition, many small blood clots are released into the body that in turn can reach the brain.

“Simply put, the brain gets too little oxygen in patients with atrial fibrillation. Actually, this is very logical, but no one has yet managed to show this before us, says Løchen.

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Read the Norwegian version of this article at forskning.no