NEW YORK (Reuters Health) - Men with atrial fibrillation score significantly lower on cognitive performance tests than their peers without this dangerous heart arrhythmia, according to an analysis of data for men enrolled in the Framingham Offspring Study.

Atrial fibrillation is a condition in which the heart's upper chambers quiver instead of beating regularly. This arrhythmia increases the risk of stroke, heart failure, cognitive impairment and death.

"A variety of factors linking atrial fibrillation to decreased cognitive performance have been suggested, including undiagnosed stroke, lesions on the brain, and reduced cardiac output," lead author Dr. Merrill F. Elias, from Boston University, said in a statement.

"What we need now are additional studies that will hopefully lead to a better understanding of the underlying mechanisms that cause men with atrial fibrillation to have poorer cognition."

Elias and colleagues used standard tests to compare cognitive function in 59 men with atrial fibrillation and 952 with normal heart rhythm. All of the subjects were stroke-free and dementia-free.

After adjusting for age, education, stroke risk factors, and cardiovascular disease, men with atrial fibrillation had significantly lower performance on global cognitive ability than control subjects.

The authors also found that atrial fibrillation patients scored lower a number of specific cognitive tasks, including abstract reasoning, visual memory, visual organization, verbal memory, scanning and tracking, and executive functioning.

"Our community-based study highlights the importance of the association between atrial fibrillation and multiple cognitive abilities in the absence of stroke and dementia," the authors state. "The risk of performance in the lower quartile of global ability was raised fourfold by the presence of atrial fibrillation."