What makes one person's mind remain sharp as a tack despite the passing years...while another person's memories and mental powers grow dull...and still another develops full-blown dementia? In many cases, the answer is a mystery. But now we have a new clue that could help protect brainpower. Researchers recently discovered that a common problem with the electrical system that controls heart rhythm may account for cognitive decline in a sizable portion of people. That's right—the way your heart beats could be severely harming your brain. And the insidious thing is, because this electrical heart glitch can be very subtle (often causing no symptoms, in fact), many people don't realize that they have the problem...while others have no idea that they're at risk of developing it. The heart rhythm problem is called atrial fibrillation, and it's very common. Here's what you should know about how your heart could be slowly, silently harming your brain. LOOKING FOR A LINK Researchers used data collected during the Cardiovascular Health Study that began in 1989 and enrolled 5,150 adults ages 65 and older. At the time the study began, none of the participants had ever been diagnosed with atrial fibrillation. More on Atrial Fibrillation Atrial Fibrillation: A Hidden But Deadly Heart Problem Too Many Drinks Linked with Atrial Fibrillation New and Serious Risk for Arthritis Sufferers: Atrial Fibrillation Blood Thinners for Atrial Fibrillation Patients? A New Tool Shows Who Benefits...and Who Doesn’t Heart-Rhythm Problem? These Supplements Can Help Yoga Helps Atrial Fibrillation At the beginning of the study and again each year for the next nine years, participants had electrocardiograms (ECG) to look for any problems with heart rhythm. They also had annual cognition tests that evaluated memory, verbal fluency, calculation skills and more. Possible scores ranged from zero (the worst) to 100 (the best). By looking at the ECGs or hospital records, the researchers determined that 11% of the participants developed atrial fibrillation during the follow-up period. After adjusting for risk factors such as other health problems, age and lifestyle, the researchers used the cognitive test scores to compare the mental function of people who developed atrial fibrillation with people who did not have atrial fibrillation. They found obvious differences in the rates of mental decline.