Cardiac index - the measure of how well the heart is pumping blood to the brain and the rest of the body - may be a future indicator of a person's risk for developing dementia.
A study in this week's Circulation suggests cardiac index is linked to brain size, even in people without heart disease, a known risk factor for dementia.
"The primary factor is that cardiac index is associated with brain volume. Participants with low cardiac index and low normal values had smaller brains, equivalent to about two years of brain aging compared to those with high cardiac index," says study author Angela Jefferson, associate professor of neurology at the Alzheimer's Disease Center at Boston University School of Medicine.
The study evaluated data from 1,504 participants in the Framingham Offspring Cohort, an arm of the larger Framingham Heart Study. Information was collected from neuropsychological tests, brain and cardiac MRI and lab reports.
Doctors have long known the heart and brain are intertwined, and that heart disease is a risk factor for dementia and Alzheimer's, says Richard Lipton, an attending neurologist at Montefiore Medical Center and professor of neurology at the Einstein College of Medicine in New York. But he says these results take into account non-heart patients, too.
"These are not people with heart disease, so that's what makes it interesting," says Lipton.