Bradley Hatfield has found that even for people who haven't been exercising, it might not be too late.
"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," he said.
"Therefore, we are using neuro-imaging 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," he added.
Hatfield also said that the research has found that exercise has a protective effect on brain.
"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 neuro-degeneration in the memory-related regions of the brain," he said.
"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.
"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.
" 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," he added.