VANCOUVER, B.C. – Physical activity improves not only the heart and lungs, but the brain as well, providing a triad of benefits: improved cognition, better physiologic functioning, and increased brain volume and hints of revved-up neuronal growth.
Studies presented July 15 at the Alzheimer’s Association International Conference 2012 agreed: Getting active is essential for preserving cognitive health.
Exactly how exercise boosts brain function is still a matter of debate, Teresa Liu-Ambrose, Ph.D., said in an interview.
"In addition to getting the physical benefits of exercise, people are also getting social interaction and mental stimulation," said Dr. Liu-Ambrose, director of the Aging, Mobility, and Cognitive Neuroscience Lab at the University of British Columbia, Vancouver. Group activities, like exercise, can also help unwind the tangle of diminished executive function and social isolation, a damaging pair.
"When executive function begins to deteriorate, people know that they are losing some of their ability to interact, and so they withdraw and become isolated," she said. The lack of social interaction contributes to the downward slide of cognition.
Dr. Liu-Ambrose was the primary investigator of a randomized controlled trial that examined the benefits of three different exercise regimens, each conducted twice a week for 6 months: resistance training; aerobic training; and balance and tone training, which served as the comparator group.
The subjects were 86 women aged 70-80 years. They all still lived at home, but had probable mild cognitive impairment. The group is an important one because the natural history of Alzheimer’s disease suggests that about half of those who develop mild cognitive impairment will go on to develop Alzheimer’s dementia.
All of the programs were progressive, she said. Those in the weight program started with the largest weights they could handle with good form, which were increased as soon as the women exceeded the required number of repetitions. The aerobic group increased their walking speed based on heart rate and perceived exertion. The control group loaded their exercises as well, increasing repetitions and stretching as the trial progressed.
After 6 months, the strength training group had improved by 17% over baseline on measures of executive function, which was significantly better than either of the other groups. These women also experienced significant gains in associative memory.
Dr. Liu-Ambrose also saw physiologic correlates to the cognitive findings. Functional MRI showed improved blood flow in three brain regions involved with encoding and memorization of nonverbal associations: the right lingual gyrus, the occipital fusiform gyrus, and the right frontal pole.
The aerobic training group improved in balance, mobility, and cardiovascular capacity, but did not have the same kind of cognitive or brain physiologic gains, she added. The balance and tone group maintained their cognitive ability without any additional decline, but didn’t experience any additional benefit either.
"I want to stress that we were seeing a real improvement with resistance training – not just maintenance like we did in the control group. We’re talking about women who already have some level of cognitive impairment. The most positive way of looking at this is that exercise could be a magic bullet. There is evidence now that exercise may not only be preventive – but a potential treatment."
In a separate study, Kirk Erickson, Ph.D., presented evidence of the molecular underpinning of exercise-induced brain volume changes: Physical activity, he said, stimulates the release of molecules that promote neuronal growth.
Dr. Erickson, a cognitive neuroscience researcher at the University of Pittsburgh, described the results of a walking program that involved 120 cognitively healthy, elderly adults.
The participants had been sedentary for at least the previous 6 months. They were randomized either to a 1-year program of moderately intense walking or to a 1-year stretching and toning group. At baseline and at 1 year, Dr. Erickson and his colleagues measured brain volume and levels of brain-derived neurotrophic factor (BDNF).
BDNF is a protein that affects neurons in several ways: It supports healthy neuronal function, encourages stem cells to differentiate into neurons, and stimulates dendritic expansion. BDNF is particularly active in regions associated with memory and executive functioning.
At the study’s end, Dr. Erickson and his associates found that those in the walking program had about a 2% increase in the size of the anterior hippocampus, compared with the stretching and toning group. Increases in BDNF positively correlated with the volume change. He also saw increases in the volume of the prefrontal cortex, which correlated with increased cardiorespiratory fitness.
Just how to translate these controlled experimental situations into effective, real-life practice isn’t completely clear, Dr. Liu-Ambrose said, especially when patients already have difficulty with planning and prioritization.