Reduced Heart Function Can Lead to Brain Atrophy, Dementia
People with hearts that pumped blood inefficiently throughout the body were found to be a greater risk for loss of brain volume and possible eventual dementia, according to a new study conducted at the Boston University School of Medicine.
Good for the Heart, Good for the Brain
Angela L. Jefferson PhD and colleagues examined brain and heart MRI data on 1504 patients between the ages of 34 and 84 (average 61) without a history of neurologic disease enrolled in the Framingham Offspring Cohort study. Fifty-four percent were women. About 7% of the volunteers had known heart disease, but anyone with significant cardiovascular problems were excluded from the study. The participants were divided into three groups based on their cardiac index, or the pumping ability of the heart.
Cardiac index is a calculation that takes into account body surface area, stroke volume (the volume of blood pumped from one heart ventricle with each beat), heart rate and cardiac output (the volume of blood pumped by a ventricle in one minute). Reduced cardiac output can be influenced by heart disease, hypertension, and infection.
Participants whose hearts pumped the least amount of blood showed almost two years more brain aging than those with hearts that pumped more. Even those on the low end of normal had lower brain volumes than those in the upper third. Jefferson theorizes that the lower volume of pumping blood may reduce blood flow to the brain, providing less oxygen and nutrients.
A decrease in brain volume, called atrophy, is considered a sign of brain aging. More severe brain atrophy occurs in people with dementia, such as Alzheimer’s Disease.
The impact on the brain was stronger for study participants under the age of 60. The authors suggest that one reason for this finding may be that as people get older, they have more competing brain health factors.
Heart disease did not account for the all of the people with low cardiac index. As mentioned, 7% of the participants had heart disease, but Jefferson and colleagues found low heart pumping function in 30% of the volunteers.
“These participants are not sick people,” said Dr. Jefferson. “A very small number have heart disease. The observation that nearly a third of the entire sample has low cardiac index and that lower cardiac index is related to smaller brain volume is concerning and requires further study.”
"This is an interesting, strong association. Just as we measure someone's weight, blood pressure and cholesterol to assess their heart disease risk, we now have numbers for cardiac index and brain volume. But, we're still at the association stage, and can't tell if one factor is caused by the other," said Dr. Ralph Sacco, president of the American Heart Association and co-author of an accompanying editorial.
"Our results definitely suggest that cardiac health is related to brain health," Jefferson noted. Controlling heart disease risk factors by exercising regularly, eating right, maintaining a healthy weight, not smoking, and managing conditions such as high blood pressure and diabetes will lead to better cardiovascular and brain health.
Jefferson AL, et al "Cardiac index is associated with brain aging: The Framingham Heart Study" Circulation 2010; DOI:10.1161/CIRCULATIONAHA.109.905091.
Wright CB, Sacco RL "Cardiac index as a correlate of brain volume: Separating the wheat of normal aging from the chaff of vascular cognitive disorders" Circulation 2010; DOI:10.1161/CIRCULATIONAHA.110.970301.