People with atrial fibrillation tend to have faster cognitive decline, even among those who have not experienced a stroke, researchers from the University of Alabama at Birmingham reported in the June 5th issue of Neurology.

Atrial fibrillation is an irregular heart rhythm caused by chaotic electrical signals, which are generated in the atria (chambers) of the heart. Atrial fibrillation raises the risk of stroke, heart failure, blood clots and other cardiovascular complications. Approximately 2.7 million people in the USA today live with atrial fibrillation.

Lead author, Evan Thacker, Ph.D., and team set out to determine whether atrial fibrillation patients with no history of stroke had more rapid cognitive decline after diagnosis. Cognitive decline refers to problems with memory or thinking.

Researchers already knew that dementia risk is much higher in people with stroke and atrial fibrillation, but few had set out to determine whether atrial fibrillation patients who had not experienced a stroke might suffer from faster cognitive impairment.

In November 2012, researchers from Texas Cardiac Arrhythmia Institute, St. David’s Medical Center in Austin, Texas, uncovered an independent association between atrial fibrillation and dementia in older adult population. They reported the findings of their study, which involved over 77,000 patients, in the medical journal HeartRhythm.

Thacker said:

“We found that age-related declines in average cognitive test scores did occur faster after diagnosis of atrial fibrillation, even after accounting for other factors that can hasten cognitive decline.

This means that people with atrial fibrillation may, on average, reach a state of significant cognitive impairment or dementia at earlier ages than people without atrial fibrillation.”

Thacker and colleagues gathered and examined data on about 5,000 seniors registered in the Cardiovascular Health Study. They were given a 100-point thinking and memory test annually for seven years (average). During that period 11% of them developed atrial fibrillation.

The researchers found that:

  • Patients whose atrial fibrillation was diagnosed when they were 80 had a 10-point drop in their cognitive scores during the following five years
  • Patients of the same age without atrial fibrillation had a 6-point decline in their cognitive scores
  • Rates of decline in test scored differed according to people’s age
  • In a different brain function test (top score of 90) patients diagnosed with atrial fibrillation at 80 had average declines of 7 points over the following five years, compared to 5 points among those of the same age without irregular heart rhythm

Thacker said “We believe there are at least two possible explanations for our findings. The first is that small blood clots form in the heart and then lodge in the brain, not causing any immediate symptoms, but leading to damage over time. The other is that low output of blood to the brain from the irregular heartbeat may lead to small brain damage that builds up over time.”

The researchers said they aim to find out why atrial fibrillation patients experience faster cognitive decline by using brain imaging technology to physically see what is going on inside patients’ brains. Thacker said “If we could discover the reason, then we might be able to conceive ways to prevent or reduce cognitive decline in people with atrial fibrillation.”

Atrial fibrillation prevalence is expected to increase globally as the world population ages. According to some studies, over the next three to four decades the number of people diagnosed with the disease in the USA is expected to more than double. The prevalence of dementia worldwide is also expected to increase significantly.

Written by Christian Nordqvist