Fran Lowry

February 3, 2011 — Aerobic exercise training that gets sedentary older adults up and walking for 40 minutes 3 times a week has been shown to increase the size of the hippocampus and improve memory after 1 year.

The findings appear in the January 31 issue of the Proceedings of the National Academy of Sciences of the United States of America.

“There are 2 very important messages to take home from this study,” leadinvestigator Kirk Erickson, PhD, professor of psychology at the University ofPittsburgh in Pennsylvania, told Medscape Medical News. “The first is that the brain remains modifiable until late adulthood, and this gives us a lot of promise for interventions and treatments that could prevent or delay or even reverse atrophy of the brain. The second major message is that it’s never too late to start exercising.”

Dr. Erickson and his colleagues recruited 60 adults aged 60 to 80 years who got 30 minutes or less of physical activity per week to embark on a course of aerobictraining that involved a program of brisk walking. A similar number of sedentary adults who served as controls were randomized to stretching and toning exercises.

“They were fairly inactive individuals, which is unfortunately very common in society, but nonetheless, we brought them in and started them walking. We first started them walking 10 to 15 minutes at a time because they were not used to exercise, and eventually we progressed them to about 40 minutes a day for 3 days a week and that lasted for a year,” he explained.

The participants were supervised, accompanied by trained personnel who monitored their heart rate and level of exertion. All had experienced some degree of brain atrophy although this had not yet progressed to a diagnosis of dementia, and were otherwise healthy, albeit with the usual complement of aches and pains typical for a population of this age, Dr. Erickson said.

In addition, all had to get approval from their personal physicians to participate in the study.

Magnetic resonance images (MRIs) were collected before the intervention, after 6 months, and again after the completion of the program.

“MRI allowed us to get very high-resolution, detailed images of their brain, and then we were able to use some algorithms to segment out certain brain regions and calculate the size of the hippocampus,” Dr. Erickson said.

In addition, participants were given a memory test that measured their spatial memory at the same 3 time points in the study.

Both groups were similar with regard to their hippocampal volume and memory at baseline.

At the end of 1 year, participants in the aerobic exercise training group increased the volume of the left hippocampus by 2.12% and the right hippocampus by 1.97%, whereas the control group actually displayed a 1.40% and 1.43% decline in the left and right hippocampus, respectively.

The study also found that those in the aerobic exercise group showed improved memory function compared with their performance at the start of the study. This improvement was associated with the increased size of the hippocampus. Increased hippocampal volume was also associated with greater levels of brain-derived neurotrophic factor, a small molecule involved in learning and memory.

“Up to now, we have never demonstrated that if we take people who are previously sedentary and give them exercise that we can actually increase the size of this region of the brain,” said Dr. Erickson.

“Clinicians should really try to get their older patients moving. It’s easy for us to think that exercise only exerts its effects on our bodies from the neck down, but clearly that’s not the case. Our brains are parts of our bodies, and we see the same types of benefits on our brains as we do our bodies. I think that is easily overlooked and something we don’t often think about.”

Cyrus Raji, MD, PhD, a researcher at the University of Pittsburgh who has conducted research on the benefits of exercise for Alzheimer’s disease, commented that the study is important because it shows in a very concrete way how beneficial exercise can be for seniors.

“This is a randomized clinical trial, which is the highest form of clinical investigation you can have. What was most exciting to me about the study is that they showed that the specific part of the hippocampus, the anterior part of the hippocampus, benefits the most from exercise training,” Dr. Raji, who was not part of the current study, told Medscape Medical News.

“This is important because Alzheimer’s disease is known to start in and target that part of the hippocampus. The finding helps explain how exercise can reduce the risk for Alzheimer’s disease and is another reason why everybody of all age groups, but especially the elderly, should, based on this study, engage in regular forms of physical activity.”

Proc Natl Acad Sci U S A. Published online January 31, 2011.