Atrial Fibrillation (AF) May Speed Onset of Cognitive Decline According to New Analysis from the Cardiovascular Health Study
By Peggy Noonan
August 21, 2013
- Summary: New research shows people with atrial fibrillation (AF) may develop cognitive decline at a younger age than those without afib and this finding may lead to new approaches for treating afib
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People with atrial fibrillation may develop age-related cognitive decline at a younger age than those without afib, a new study says.
We already knew that cognitive decline, or thinking and memory problems, are more common as people get older. We knew that afib also is more common with age. And we knew that stroke, which is also linked to afib, is a known contributor to cognitive decline. But the research that pointed to these associations was not set up in a way that would reveal whether afib was coincidental or actually played a part in speeding up age-related cognitive decline.
Sharper focus finds clues
To find out, researchers designed a new study. The goal was to find out whether afib affects the speed at which people develop cognitive decline, explains lead author Evan L. Thacker, PhD, Assistant Professor in the Department of Health Science at Brigham Young University in Provo, Utah. When the study was published, Thacker was a statistician in the University of Alabama at Birmingham (UAB) Department of Epidemiology. Prior to that, his research was conducted in the Department of Epidemiology at the University of Washington.
His team conducted a longitudinal analysis of data collected on men and women age 65 and older who participated in the seven-year Cardiovascular Health Study. Participants’ cognitive abilities were tested annually up to 9 times using the 100-point Modified Mini-Mental State (3MS) examination and the 90-question Digit Symbol Substitution Test.
Next, they winnowed out participants who had been diagnosed with afib and related conditions such as heart disease, hypertension, diabetes, and stroke. The goal was to see whether afib itself affected cognitive decline. After exclusions, the study looked at a total of 5,150 participants. Of that number, 552 (10.7 percent) developed afib after the study began.
Results may help find treatment
“Based on prior studies that had been done on this topic, we expected to see faster cognitive decline in people with afib, on average, compared with people the same age without afib,” Thacker says. “And that is exactly what we saw.” The study produced no surprises, but it did what they hoped it would, he adds. “We were able to see this relationship of afib with faster cognitive decline more clearly and convincingly than had ever been shown in previous studies.”
One of the findings was that over a five year period between ages 80 and 85, cognitive test scores declined by 10.3 points in those who developed afib, but declined only 6.4 points in people in the same age group who did not develop afib.
What could account for this apparent afib link?
The researchers think two explanations may be possible. One is that people with afib may develop small blood clots that form in the heart and then lodge in the brain, but that are small enough to not cause any immediate symptoms, though their presence leads to damage over time. The other possibility is that low blood output to the brain caused by afib’s characteristic irregular heartbeat may lead to “small brain damage that builds up over time,” Thacker says.
If we can find the reason, it might be possible to find ways to prevent, or at least reduce, cognitive decline in people with afib, Thacker says.
One size does not fit all
But there’s one very important point that Thacker wants to be sure people understand. “Our research was based on what happens on average in large groups of people,” he says. That was the only way to see this average decline with afib. But, he says emphatically, this study’s findings do “not mean that any individual with afib will develop cognitive decline, or [will] have cognitive decline faster than people without afib.” As he points out, “many participants remained cognitively healthy throughout the study, whether they had afib or not.” And some had both afib and cognitive decline while others had cognitive decline without afib.
In other words, this research should not be taken as a one-size-fits-all finding.
Thacker has several ideas for new research projects that might help us learn more about the afib-cognitive decline connection. “One idea is to use brain imaging such as MRI in afib patients to learn more about changes in the brain, over time, that may be due to afib.” Another is to see whether anticoagulant medicines used to treat afib, such as warfarin (Coumadin), dabigatran (Pradaxa), rivaroxaban (Xarelto), or apixaban (Eliquis) would reduce cognitive decline in people with afib.
These promising avenues of research may lead to better approaches to treating atrial fibrillation.
One of the questions I frequently have when research shows cognitive decline and dementia in those with afib is whether the side effects from certain medications, such as brain fog from beta blockers, could be mimicking permanent cognitive decline. This is something Dr. Thacker and I have been discussing for a while, but researching this is a lot more challenging than you might think. Stopping these medications might reverse this effect, but could also be highly detrimental to those with afib in whom beta blockers protect the heart, keeping the fast heartbeat from being transmitted to the ventricles and thus causing serious issues such as ventricular fibrillation and/or sudden cardiac death. Much research is needed to give us definitive answers about the connection between afib and cognitive decline.
To learn more, see:
- Atrial Fibrillation and Cognitive Decline A longitudinal cohort study, Neurology, 2013;81:1-7
- Abnormal heartbeat condition linked to cognitive decline, University of Alabama, news release, June 5, 2013
- Rapid, Irregular Heartbeat May Be Linked to Problems with Memory and Thinking, American Academy of Neurology, news release, June 6, 2013