Exercise Improves Old Brains

Dan Peterson

Date: 05 January 2009 Time: 05:52 AM ET

The moment of truth has arrived, again. The holidays have passed, the leftovers are dwindling and you have renewed your annual New Year's resolution to get back into shape... for real. Don't worry, you are not alone. According to the Centers for Disease Control (CDC), 63 percent of Americans have a Body Mass Index (BMI) in excess of 25 (defined as overweight), while a quarter are greater than 30 (obese).

As we get older, those extra pounds start to affect other areas of our health, contributing to the onset of diabetes, hypertension, high cholesterol and even sexual function.

Several new studies in the last month have now built stronger links between our levels of physical activity and the health of our most important body part, the brain. Conditions such as dementia, Parkinson's, Alzheimer's and even mild age-related memory loss can be delayed by regular physical activity.

Shrinking brain

According to John Ratey, clinical associate professor of psychiatry at Harvard Medical School and author of "Spark: the revolutionary new science of exercise and the brain" (2008, Little, Brown), "Age happens. Getting older is unavoidable, but falling apart is not."

Starting at age 40, we lose about 5 percent of our brain volume per decade, but then at age 70 other conditions may start to accelerate the deterioration. As we age, our cells are less able to cope with stress from waste products such as free radicals.

In the brain, as this stress claims more neuron cells, the web of interconnections between neurons weakens. As we each have more than one hundred billion neurons with each having oodles of connections to other neurons, this gradual net loss is not as dramatic, at first. However, as we age, if this neurodegenerative process accelerates, then our general focus and memory loss as well as more serious conditions like Alzheimer's may appear.

What the aging brain needs is a pumped-up blood flow. Exercise-induced neurotrophins such as brain-derived neurotropic factor (BDNF), vascular endothelial growth factor (VEGF), as well as the neurotransmitter dopamine are needed to grow and fertilize new and existing neurons and their synapse connections. Ratay calls BDNF "Miracle-Gro for the brain."

Make new brain cells

Researchers at the National Cheng Kung University Medical College in Taiwan recently tested the effects of BDNF in the brains of mice of different ages. Half were trained to run a maze for 1 hour a day for exercise, while the control group did not exercise.

As expected, the researchers first found that neurogenesis, the creation of new neuron cells in the brain, dropped of dramatically in the middle-aged mice compared with younger mice. They also were able to conclude that exercise significantly slows down the loss of new nerve cells in the middle-aged mice.

Production of neural stem cells improved by approximately 200 percent compared to the middle-aged mice that did not exercise.

Increase blood flow

Mice are thought to be a good analog for humans. But of course they are not human.

However, University of North Carolina brain researchers recently found that older adult humans who regularly exercised had increased blood flow in their brains. They compared long-time exercisers with sedentary adults using 3D MRI brain-scanning techniques.

"The active adults had more small blood vessels and improved cerebral blood flow," said the study's senior author, J. Keith Smith, associate professor of radiology at UNC School of Medicine. "These findings further point out the importance of regular exercise to healthy aging."

The research builds on a host of other studies, summarized in an August review, that show a balanced diet and regular exercise can protect the brain and ward off mental disorders.

Helps manage glucose

Finally, in a report released last week, Scott A. Small, associate professor of neurology at Columbia University Medical Center, found that levels of blood sugar (glucose) have a direct effect on blood flow in the brain.

By testing 240 elderly volunteers, and using functional magnetic resonance imaging (fMRI), Small and his colleagues found a correlation between elevated blood glucose levels and decreased cerebral blood flow, in the dentate gyrus, an area in the brain's hippocampus that has a direct effect on our memories. This corresponds with Smith's findings by showing that exercise may help manage glucose levels, which will improve blood flow to the brain.

Small's previous imaging studies have shown that physical exercise causes an improvement in dentate gyrus function.

"By improving glucose metabolism, physical exercise also reduces blood glucose" Small said. "We have a behavioral recommendation — physical exercise."

Dan Peterson blogs about sports science at his site Sports Are 80 Percent Mental and at Scientific Blogging.