Walking on a treadmill for 30 minutes a day 4 days a week over a 12-week period improved memory scores and neural efficiency in older people with mild cognitive impairment (MCI), according to new research.
The finding suggests that exercise may protect against or delay conversion to Alzheimer's disease in at-risk individuals.
"We found that after just 12 weeks of being on a moderate exercise program, participants improved their neural efficiency; they were using fewer neural resources to perform the same memory task," J. Carson Smith, PhD, from the University of Maryland in College Park, told Medscape Medical News.
The study is published in the August issue of the Journal of Alzheimer's Disease.
Gradual Increase in Intensity
Dr. Smith, a kinesiologist, said he has long been interested in finding out whether exercise could be useful in helping people who already are experiencing memory problems that go beyond the usual lapses of memory associated with normal aging.
"We often recommend physical exercise for people diagnosed with MCI because it has been reported to produce cognitive benefits in healthy older adults. We wanted to see if it really could have a beneficial effect on brain function in MCI," he said.
Seventeen participants had MCI, and 18 were normal age-matched control particpants.In the study, Dr. Smith and his colleagues recruited community-dwelling older adults aged 60 to 88 years who reported that they engaged in fewer than 3 days of moderate-intensity physical activity per week.
All of the study participants underwent a comprehensive neuropsycholgical test battery before and after the exercise intervention. Among the tests were the Mini–Mental State Exam, the Rey Auditory Verbal Learning Test (AVLT), and the Mattis Dementia Rating Scale–2 (DRS).
In addition, alternate forms of the AVLT and the DRS were used at the pre- and postintervention test sessions.
The exercise component of the study consisted of 44 sessions of treadmill walking that were supervised by a qualified personal fitness trainer during a period of 12 weeks.
The exercise intensity, session duration, and weekly frequency were gradually increased during the first 4 weeks until the participants were walking 30 minutes per session 4 times a week at an intensity of approximately 50% to 60% of heart rate reserve during weeks 5 to 12.
Both MCI and control participants significantly increased their cardiorespiratory fitness, as shown by improvement in peak aerobic capacity (VO2peak), by approximately 10% (P = .004) from baseline.
The researchers also found that memory scores on the AVLT test, which required that participants repeat a list of 15 words that was read to them, significantly improved among the MCI participants (P = .006) from baseline.
"The MCI group improved with the exercise. Before the intervention, they could remember 4 words, and after, this went up to 5 words, which was a significant improvement for them," Dr. Smith said.
"They are not losing memory like they were before. It is quite remarkable, in fact, because these people are expected to continue to lose memory function, and we showed that we could reverse that."
Slow Progression to Alzheimer's?
Exercise could benefit cognitive function a number of ways, Dr. Smith said.
"It's difficult to know for sure, and exercise affects every system in the body almost simultaneously, so to try to isolate what exactly is going on is difficult."
Studies in animals suggest that neurogenic and neurotrophic factors increase brain tissue growth. These growth factors can cause new synapses to form in the brain.
"This has been particularly shown to happen in the hippocampus, the part of the brain that is affected in Alzheimer's disease. Exercise has been shown to increase the size of the hippocampus, so that may be part of the reason for the improvement in memory," Dr. Smith said.
The improvement may also be due to increased blood flow and blood volume in the brain, which would boost the health of the neurons and bring them more nutrients.
The increased blood flow may also help to counteract the buildup of amyloid plaque that occurs in Alzheimer's disease, he said.
Encouraged by these results, Dr. Smith said he and his team plan to do this study in a larger group of people and to follow them for a longer period.
"Our hope is to see whether or not the exercise can actually slow down their progression to Alzheimer's disease and perhaps even prevent them from being diagnosed with Alzheimer's disease," he said.
Healthy Lifestyle Message
Commenting on this study for Medscape Medical News, Karen Miller, PhD, from the University of California, Los Angeles (UCLA) Longevity Center, said the study "is a worthwhile publication, as it extends our scientific knowledge on how lifestyle changes, including exercise, can promote brain fitness even among those with mild memory problems who are often at the greatest risk for developing dementia."
Dr. Miller added that the take-home message from this study is that individuals need to look at all aspects of their life "to promote better cognition and memory, including reducing vascular risk factors by controlling high blood pressure, increasing exercise, eating brain-healthy foods such as foods containing antioxidants, and participating in cognitively stimulating activities, such as taking a class, doing computerized brain fitness programs, and learning a foreign language."
Dr. Smith reports no relevant financial relationships. Dr. Miller reports that she is a consultant to Dakim, Inc., a producer of brain fitness computer programs.
J Alzheimers Dis. In press, 2013. Abstract
