Left Image: Normal Brain Right Image: Atrophied Brain
"Those with the lowest cardiac index and the middle group both had smaller brain volumes than those with the highest cardiac index. (Cardiac Index is the measurement of blood flow from the heart, based on one's body size.)
Our results definitely suggest that cardiac health is related to brain health.
These participants are not sick people. A very small number have heart disease.
The observation that nearly a third of the entire sample has a low cardiac index and the lower cardiac index is related to smaller brain volume is concerning and requires further study.
The structural (brain) changes may be early evidence that something is wrong. There are several theories for why reduced cardiac index might affect brain health. For instance, a lower volume of blood pumping from the heart might reduce blood flow to the brain, providing less oxygen and fewer nutrients needed for brain cells.
It is too early to dole out health advice based on this one finding, but it does suggest that heart and brain health go hand in hand."
Dr. Angela L. Jefferson, lead investigator, Boston University, "Cardiac Index is Associated with Brain Aging. The Framingham Heart Study", published online August 2, 2010, Circulation.
This just-published article in Circulation certainly got my attention. Who wants brain shrinkage a.k.a. brain atrophy? Not if there is something you can do to prevent it.
Bottom line here: Those study participants whose hearts pumped less blood, had brains that appeared older than the brains of those whose hearts pumped more blood--to the tune of two years worth of brain aging.
The biggest surprise to the researchers was that of this group of 1504 mostly healthy middle-aged volunteers--all offspring of the original Framingham Study volunteers--not only did the folks with lowest cardiac index show significant brain volume shrinkage, but so did the folks with a cardiac index in the middle range! Only those with the highest cardiac index showed significant retention of their brain volume.
"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 the very healthiest cardiac index." Dr. Angela Jefferson
The researcher's other big surprise was the high number of "normal healthy" adults who had a cardiac index below normal. Around 30% of these seemingly healthy middle-aged adults had a low cardiac index.
"In light of the current observation that cardiac index is associated with cross-sectional markers of accelerated brain aging, such a high proportion of cardiac index values below clinical criteria warrants further investigation." (excerpted from the article)
It's important to remember that these were pretty healthy participants. The study excluded anyone who had a previous history of stroke, TIAs, dementia, or significant cardiovascular disease. Only 7% of the group had any heart disease at all, 10% were smokers, 9% had diabetes, and 28% had high blood pressure. And all these risk factors were controlled & adjusted for when the results were compiled.
The researchers also tested the cognitive function of the participants with 5 different neuropsychological tests.
The good news (sort of), was that the folks with the smallest brain volumes didn't yet show any obvious cognitive deficits. But, one function, how quickly one can process information, had a positive correlation to brain volume. Less brain shrinkage equaled faster processing speed. And who doesn't have a little slow processing speed as they get older?
The bad news: The researchers question exactly how precise these standard neuropsychological tests are when it comes to picking up subtle early cognitive deficits. Were the tests powerful enough to pick up underlying deficits?
The jury's still out about the future brain function of those who exhibited decreased brain volume.
The Cardiac Output-Brain Shrinkage Connection
"We observed (that the) cardiac index is related to structural changes in the brain, but not cognitive changes. The structural changes may be early evidence that something is wrong." Dr. Angela Jefferson
Here's what the authors think might be going on: "The mechanism accounting for associations between cardiac index and markers of brain aging is unknown; however, reduced systemic blood flow may contribute to subclinical brain injury because of its impact on cerebral blood flow hemostasis.
When my mom was in her late seventies she had a CAT scan (not an MRI as in the Framingham Study) of her brain to see if there might be a reason for her strange constellation of symptoms: unexplained dizziness, some unsteadiness, a few minor falls & the occasional odd experience of her body tipping to one side while she sat on the couch.
The results: The doctor said the CAT scan didn't show a thing. She was just fine. Just normal brain shrinkage from aging--everyone has that, he told us. No one connected any dots back then that perhaps her "normal brain shrinkage" might have had something to do with her heart disease, her earlier severe blockage of the left main coronary artery, for which she had an angioplasty, or her hypertension.
Within a few years of that CAT scan her memory slowly declined, tiny subtle strokes accumulated, and the results were the usual story of a slow downward health spiral--without hope of turning it around. This new Framingham Study is one more bit of evidence that demonstrates just how interconnected brain health is to heart health. It's all in the plumbing! Consider yourself warned.What Can We Do With This Information?
Dr. Ralph Sacco, the president of the American Heart Association, and the co-author of the Circulation editorial that accompanies the Framingham article, says:
"It will take years to know the fate of all 1504 Framingham participants.
Whether lower cardiac index leads to reduced brain volumes and accelerates neurodegeneration on an eventual path to dementia is not yet clear.
What is known is that various vascular risk factors, including declines in cardiac function, are determinants of dementia--both Alzheimer's disease and variants of vascular cognitive disorders.
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.
The key message for the public is the connection between heart vascular issues and brain vascular issues.
The things that affect the heart can affect brain health.
Exercising regularly, eating right, maintaining a healthy weight, not smoking, and managing high blood pressure, cholesterol, and diabetes--will all lead to better heart, blood vessel, and brain health.
Know that these things are important, not just for the heart but also for the brain."
I got into this whole exercise-healthy-diet-gig for stroke prevention and cognitive retention. Needless to say, I'm feeling even better about staying the course. Brain shrinkage--who needs it?
Can't help wondering how the MRIs of cardiac output & brain volume would look in long-time exercisers, and for those with pristine heart health.
Skip the ice cream, cheesecake, and cheeseburger this weekend. Go out and exercise. If not for your heart, then for your brain.
To read more about the heart-brain health connection read: Concerned About Brain Health, Alzheimer's or Dementia? Some Q & A with Dr. Randolph Schiffer of the Cleveland Clinic Lou Ruvo Center for Brain Health