Irregular Heartbeat May Speed Memory Loss in Seniors
Study found that people with atrial fibrillation showed mental declines at earlier age than those without heart condition
Wednesday, June 5, 2013
"Problems with memory and thinking are common for people as they get older," said lead researcher Evan Thacker, a statistician in the department of epidemiology at the University of Alabama at Birmingham. "Our study shows that, on average, these problems may start earlier or get worse more quickly in people who have atrial fibrillation. This means that heart health is an important factor related to brain health."
As with other such studies, this one established only an association between atrial fibrillation and mental decline, not a direct cause-and-effect relationship.
That's why the next step is to find out why people with atrial fibrillation start to struggle with memory and thinking sooner, Thacker said.
There are at least two possibilities, he said. First, people with atrial fibrillation may have small blood clots form in the heart that then become lodged in the brain.
"These may be too small to cause noticeable strokes, but may over time cause small damage to the brain that would eventually lead to mental decline," Thacker said.
Second, people with atrial fibrillation may simply have less blood flowing to the brain, he said.
"This could result in the brain not getting as much oxygen and nourishment as it needs, which could lead to damage over time that would result in mental problems," Thacker said.
"Currently, we do not know whether either of these two possibilities actually occurs," he said. "We would like to study it using brain imaging technology to learn more about what is happening in the brains of people with atrial fibrillation."
Eventually, if doctors and researchers can discover why people with atrial fibrillation show accelerated mental decline, they might be able to learn how to prevent the problem, Thacker said.
The report was published online June 5 in the journal Neurology.
Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, said, "Atrial fibrillation is present in close to 3 million men and women in the United States and increases the risk of stroke fivefold compared to the general population."
In addition to the marked increase in the risk of stroke, more recent research suggests that atrial fibrillation is associated with an increased risk of mental decline and dementia, he said.
"Repetitive, small subclinical strokes in patients with atrial fibrillation may account for these findings," Fonarow said.
He said giving blood thinners to patients with atrial fibrillation is standard care to prevent clots in the heart from migrating to the brain.
Putting these patients on anticoagulants, such as warfarin or one of the newer therapies, will "likely be effective in not only reducing the risk of stroke, but also reducing the significant risk of mental decline and dementia," he said.
To see the effect atrial fibrillation had on memory and thinking, Thacker's team collected data on more than 5,000 people aged 65 and older who took part in the Cardiovascular Health Study.
At the start of the study, none of the participants had atrial fibrillation. Over an average of seven years of follow-up, more than 550 people developed the condition, the researchers noted.
Each year during the study, all the participants were given a 100-point memory and thinking test.
The researchers found that people with atrial fibrillation were more likely to have lower scores on the test at an earlier age, compared with those who didn't develop atrial fibrillation.
For example, the average score on the test decreased by about six points for people without atrial fibrillation between ages 80 and 85, compared to about 10 points for those with atrial fibrillation.
For those aged 75 and older with atrial fibrillation, the average decline was about three to four points faster every five years, compared to people without atrial fibrillation.
Scores below 78 points are associated with dementia, Thacker said.
The researchers predicted that on average, those without atrial fibrillation would score below 78 when they were 87, while people with atrial fibrillation would score below 78 when they were 85.