Every Beat Counts

What’s bad for your heart may also be bad for your brain, according to a recent BU study that found a close link between recurrent irregular heartbeat and lower mental performance in men.

“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,” says Merrill Elias (SPH’96), a College of Arts Sciences research professor of epidemiology in the statistics and consulting unit and leader of the research team.

Atrial fibrillation, a condition in which the heart’s upper chambers beat irregularly and often too rapidly, “has serious consequences,” says Elias, “especially if not controlled, for blood flow to the brain, because it results in clotting of the blood as it exits the heart.”

The researchers hypothesize that the link between atrial fibrillation and lower cognitive performance may be because of structural and functional changes in the brain that are not easily detected. Atrial fibrillation can be treated with drugs, surgery, and pacemakers, however, and interventions early in the process of cognitive decline are most likely to be successful.

The researchers scrutinized a subset of the 5,124 participants in the Framingham Offspring Study, which is part of the Framingham Heart Study, a National Heart, Lung, and Blood Institute (NHLBI) initiative that has tracked the health of families in Framingham, Mass., since 1948. BU has run the Framingham Heart Study with the NHLBI since 1971. 

Using tests that measure verbal, logical, and mathematical reasoning, the researchers compared cognitive function in 59 men with atrial fibrillation to that of 952 men with healthy hearts, and found that those with atrial fibrillation performed worse in abstract reasoning, visual memory, visual organization, verbal memory, scanning and tracking, and executive functioning. The study results appeared in the September-October issue of the Journal of Stroke and Cerebrovascular Disease.

Although the subjects had no history of stroke or dementia, the tests’ results showed patterns of cognitive deficits similar to — but not as severe as — those of patients with clinical dementia. Reduced cognitive function related to a cardiovascular risk factor “could be interpreted as a potential intermediate stage” of dementia, according to Rhoda Au (SMG’95), an associate professor of neurology at the BU School of Medicine.

“There is a general belief in the research community that cardiovascular risk factors play a role in increased risk for dementia,” Au says, “particularly vascular dementia, and possibly Alzheimer’s disease.”

Indeed, because past research suggests a link between atrial fibrillation and dementia, “it’s useful to examine the relation of precursors to reduced cognitive function prior to the development of overt dementia,” says Emelia Benjamin, a MED professor of clinical cardiology.

The subjects of the Framingham Offspring Study are “ideal for this research,” says Au, because these children of the original cohort have had health exams every four years, beginning in 1976, and the researchers have recently been studying incident cases of dementia in the group. “The extensive database we have to draw on is unprecedented,” she says.  Only men were included in the study because women are less likely to be affected by atrial fibrillation.

The other researchers involved in the study are Lisa Sullivan, chair and associate professor of the School of Public Health department of biostatistics, Ramachandran Vasan, a MED professor of medicine, Philip Wolf, a MED professor of neurology, Sudha Seshadri, a MED assistant professor of neurology, Ralph D’Agostino, a CAS professor of mathematics and statistics, and Penelope Elias, a psychology professor at the University of Maine.

Brian Fitzgerald can be reached at bfitzger@bu.edu.