Benefits of exercise on the aging brain

Oct 15 2007

Bradley Hatfield, professor in the University of Maryland, College Park, School of Public Health, uses high tech brain imaging to study the benefits of exercise on the aging brain.

In this Q&A, Hatfield describes his early results, which show that moderate physical activity may help maintain memory function longer, maybe even for years, in people with genetic predisposition to Alzheimer's Disease. More good news for boomers – even for people who haven't been exercising, it might not be too late. Media may use all or parts of this interview, with attribution to Professor Hatfield.

What are you trying to learn with your research on exercise and the aging brain?
HATFIELD: We are trying to determine if physical activity slows or delays age-related change in the brain, particularly in those who are genetically susceptible to Alzheimer's Disease. Memory-related structures are among the brain regions that are affected in the earliest stages of Alzheimer's Disease and, importantly, physical activity results in the release of neurotrophins (factors that promote growth and repair of neural tissue), particularly in these regions. This has been clearly shown in animal studies. These neurotrophins would counteract the ravages of the disease. Therefore, we are using neuroimaging to determine if these brain regions are positively affected by exercise in human subjects. Support for this prediction would imply that physical activity would be of great importance to maintain memory and cognitive function in men and women who are at genetic risk for Alzheimer's Disease. That is, it could prevent appearance of symptoms for some time - perhaps even years.

What are your methods?
HATFIELD: We use neuroimaging tools such as EEG (electroencephalography), MEG (magnetoencephalography) and magnetic resonance imaging (MRI) to take pictures of the brain both at rest and at work. We're also doing cognitive testing. We then compare the "pictures" from different groups to determine differences as related to physical activity levels and genetic factors.

How is your research different from other studies?
HATFIELD: I think the main difference is that we are using neuroimaging to assess brain activity in middle-aged men and women who are cognitively intact but differ in their genetic risk for Alzheimer's Disease. That is, we can detect differences in brain processes as related to a sedentary lifestyle even though the cognitive performance appears normal. This is because the brain can compensate for decline, and it appears to function the same as in those who are physically active, but neuroimaging can reveal if it is working harder to overcome any deficits. This kind of inefficiency would not be discernible through cognitive or behavioral testing.

What have you found?
HATFIELD: We have found that physically active individuals, who carry the gene that makes them more susceptible to Alzheimer's (APOE e4), show brain activation profiles during memory challenge that are similar to non-carriers who are at lower genetic risk of Alzheimer's. In essence, this implies a protective effect of exercise on the brain. On the other hand, carriers of the gene who are sedentary show reduced brain activation that implies some degree of neurodegeneration in the memory-related regions of the brain.

What level of exercise seems to make the difference?
HATFIELD: It's not well established at this time, but it seems that a moderate degree of physical activity, such as brisk walking three or more times per week, for 20 minutes or more per session, is sufficient from what we know generally about physical activity and health. Much more work remains to be done.

Were there any surprises in your study?
HATFIELD: We were surprised that our study hypotheses were supported by the neuroimaging data. The human brain is a very complex structure, so it is not uncommon for study results to fail to support predictions. We still need to conduct an exercise intervention study whereas at this time we have simply compared

If I'm over 50, and I don't exercise, is it too late?
HATFIELD: We don't have definitive evidence, but the preliminary results that we do have would suggest that it is not too late. In fact, we believe that middle age may provide a "window of opportunity" during which one could capitalize on the beneficial effects of exercise on the brain and delay decline - thus maintaining a higher quality of mental life.

What studies do you have planned for the future?
HATFIELD: We plan to image the subcortical memory-related regions of the brain. At present, we have primarily examined the cerebral cortex or the covering of the cerebral hemispheres using EEG and MEG. We have just begun to examine the hippocampus, which is the gateway to long-term memory, using MRI, as it is housed deep within the forebrain and cannot be seen by EEG and MEG. No studies to date have imaged this critically important structure during memory challenge as it relates to differences in physical activity level in men and women.

We are also planning to conduct an exercise intervention or training study, in which people will be randomly assigned to exercise or control conditions in order to determine the causal or cause-effect connection between exercise and the brain. Also, in the future, we would like to assess the impact of exercise on the brain in those who are suffering from cognitive impairment- not just those who are at risk of dementia, but who are actually impaired. Perhaps exercise can substantially slow further decline and delay more serious ailment.