People in the middle of the heart assessment group, who had low but still normal cardiac index levels, also showed lower brain volumes than people with the healthiest hearts.

The participants, all between 34 and 84 years of age, half of whom were women, were divided into three groups based on the pumping ability (“cardiac index”) of their hearts. Participants whose hearts pumped the least amount of blood showed almost two years more brain aging than those with the healthiest hearts, researchers say.

Aug. 2, 2010 -- People whose hearts pump blood inefficiently may lose brain volume faster, putting them at risk for dementia , a new study indicates.

Blood Flow and the Brain

As the brain ages, it starts to shrink or “atrophy,” and the decrease in volume is considered a sign of brain aging, the researchers say in a news release. More severe brain atrophy occurs in people with dementia, such as Alzheimer’s disease.

“These results are interesting in that they suggest cardiac index and brain health are related,” Angela L. Jefferson, PhD, study author and associate professor of neurology at Boston University School of Medicine, says in the news release.

“The association cannot be attributed to cardiovascular disease because the relationship also was seen when we removed those participants with known cardiovascular disease from our analyses.”

“We expected an association between the lowest levels of cardiac index and smaller brain volumes, but we were surprised to find people on the lower end of normal cardiac index also have smaller brain volumes when compared to people with very healthy cardiac index,” Jefferson says.

Because only 7% of patients had heart disease, Jefferson and colleagues say they did not expect that 30% of people in the study would have relatively low heart pumping function.“These participants are not sick people,” she says. “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.”

Patients with smaller brain volumes did not show obvious signs of diminished brain function, the researchers say. “We observed cardiac index is related to structural changes in the brain but not cognitive changes,” Jefferson says. “The structural changes may be early evidence that something is wrong.” Those people will continue to be studied to see how structural brain changes affect memory and cognitive abilities in the future.