Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Study Suggests Link Between Brain's Blood Supply and Memory

Dear Doctor: I've read that memory is linked to the heart's ability to pump blood, with a reduced ability leading to poorer memory. Is there anything I can do to keep the blood flowing to my brain?

Dear Reader: Our brains, like the rest of our bodies, rely on optimal blood flow for optimal functioning. But in the case of the brain, that means a larger volume than you would expect. While the brain accounts for just 2 percent of a person's total weight, a series of specialized anatomical processes ensure that it gets a whopping 12 percent of the blood that flows through the body. And according to the results of an intriguing study published last fall, there appears to be a link between the brain's blood supply and cognitive function.

The study, published online in the journal Neurology, looked at a group of individuals with an average age of 73 who are taking part in the Memory and Aging Project at Vanderbilt University Medical Center in Nashville. This is an ongoing study that tracks the health and cognitive abilities of the participants and analyzes the resulting data. In this particular study, researchers selected 314 men and women, 39 percent of them diagnosed with mild cognitive impairment. That means these study subjects had exhibited a decline in memory, language, thinking or judgment that was slight but measurable. The other study participants had normal cognitive function. None had heart problems or disorders, and none had dementia.

Using imaging techniques, researchers calculated how much blood each person's heart pumped in relation to his or her body size, a value known as "cardiac index." They also measured the resulting volume of blood flow in the brain. They found that a lower cardiac index correlated to reduced blood flow to the left and right temporal lobes, the memory-processing areas of the brain. The lead author of the study characterized the resulting reduction in blood flow as comparable to what you would expect to see in individuals who were 15 to 20 years older.

All of which brings us to the heart. Reaction to the study is that the findings bolster what previous research has long suggested -- there is a strong connection between the health of the heart and the health of the brain.

But the solution may not be as simple as joining a gym or heading out for a brisk walk. That's because of those physiological mechanisms we mentioned earlier in the column, the ones that dole out a proportionally greater blood flow to the brain than to other parts of the body. Whether these mechanisms are directly affected by the health of the heart, or whether their decline is related to advancing age or the onset of cognitive decline is not yet known. The researchers themselves state that their findings reveal a link between cardiac index and blood flow to the brain, but do not suggest it is the cause.

Still, we think it wise to safeguard the health of your heart. Don't smoke, and if you do smoke, please quit. Eat well. Exercise daily. And see your family physician for an annual checkup so if a problem crops up, it can be caught early.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)