Older women with mild cognitive impairment may benefit significantly from regular aerobic exercise, new findings show. Mild cognitive impairment (MCI) is an established risk factor for dementia and “represents a vital opportunity for intervening,” say Dr. Teresa Liu-Ambrose of the University of British Columbia, Canada, and colleagues in the British Journal of Sports Medicine.
Currently, 35.6 million people worldwide have dementia and this number is expected to increase to 115.4 million by the year 2050.
“Exercise is a promising strategy for combating cognitive decline by improving brain structure and function,” they write. Aerobic training in particular may benefit otherwise healthy community-dwelling older people.
They recruited 86 women aged 70 to 80 years with probable MCI. The women undertook either aerobic training (brisk walking), resistance training (lunges, squats, and weights), or balance and tone training twice a week, for six months. The balance and tone training was not strenuous exercise, and was considered the “control” group.
At the start and the end, the women were given MRI scans of their hippocampal volume. The hippocampus plays important roles in short-term and long-term memory, and spatial navigation, and appears to be very sensitive to the effects of aging and neurological damage. Tests were also given to measure verbal memory and learning.
Compared with the balance and tone “control” group, aerobic training significantly improved left, right, and total hippocampal volumes, the team reports. “We observed a 5.6 percent increase in the left hippocampus, a 2.5 percent increase in the right hippocampus, and a four percent increase in the total hippocampus,” they write.
But they add that there was “some evidence” that increased left hippocampal volume was linked with poorer verbal memory. However, in earlier studies, increased left hippocampal volume has been linked to better performance on verbal memory tests.
“The relationship between brain volume and cognitive performance is complex, and requires further research,” say the authors.
“We might have assumed a one percent gain in hippocampal volume should improve verbal learning memory by one percent, but our results suggest that it may not be that simple,” said Dr. Liu-Ambrose. “There may be other factors we are not considering.”
Limitations of this study include the lack of male participants and those aged below 70 and over 80. But the authors do recommend regular aerobic exercise to help prevent mild cognitive decline, in addition to its many other heath benefits.
They conclude, “Aerobic training significantly increased hippocampal volume in older women with probable MCI. More research is needed to ascertain the relevance of exercise-induced changes in hippocampal volume on memory performance in older adults with MCI.”
“The degree of benefit in terms of brain structure might actually be greater in people with early functional complaints than in healthy older people,” the team adds. “Understanding the effect of exercise on the hippocampus will increase our appreciation of the role exercise may play in dementia prevention,” they conclude.
Our understanding of the impact of exercise on MCI would now benefit from studies with more participants, as well as a focus on the different MCI subtypes (single-domain versus multidomain MCI).
The intensity of aerobic exercise performed may not be crucial, according to a 2012 study. Dr. Slivia Varela of the University of Vigo, Spain, and colleages looked at the effects of aerobic exercise at two different intensities on 48 elderly people with MCI living in care homes.
Aerobic exercise at 40 percent of resting heart rate has similar effects after three months to aerobic exercise at 60 percent of resting heart rate. Both led to “marginal improvements” on cognitive level as measured by the Mini Mental State Examination, and functional ability, measured by the Timed Up and Go test.
“No statistically significant differences were found at any time during the evaluation regarding cognitive level and functional autonomy,” write the researchers in the journal Clinical Rehabilitation. “Intensity does not seem to be a determining factor when aerobic exercise is performed by people with MCI.”
Potential mechanisms behind the cognition-enhancing effects of aerobic exercise have been investigated in animal research. They include beneficial effects on neuron function, neuron inflammation, hormonal responses to stress, and the amount of amyloid in the brain. Amyloid deposits raise the risk of Alzheimer’s disease as well as brain hemorrhages.
Of course exercise also has positive effects on physiological processes such as cardiovascular health and glucose regulation that, when compromised, increase the risk of developing cognitive impairment and dementia.
Ten Brinke, L. F. et al. Aerobic exercise increases hippocampal volume in older women with probable mid cognitive impairment: a six month randomised controlled trial. British Journal of Sports Medicine, 9 April 2014, doi 10.1136/bjsports-2013-093184
Varela, S. et al. Effects of two different intensities of aerobic exercise on elderly people with mild cognitive impairment: a randomized pilot study. Clinical Rehabilitation, May 2012 doi: 10.1177/0269215511425835