Does moderate exercise delay memory decline in people at risk for Alzheimer's disease ... or anyone else?
Evidence from animal and human studies shows that exercise promotes healthy brain structures and functions, and preserves cognitive performance in older adults.
Although some clinical trials find that exercise exerts positive effects on cognitive (thinking and memory) performance, other trials show minimal to no effect.
The evidence suggests the best results flow from exercise that's structured, individualized, multi-faceted (aerobic and resistance), and of substantial intensity, duration and frequency.
Last year, a clinical trial showed that exercise improved cognitive functions in people at higher risk for Alzheimer's, by improving the efficiency of brain activity associated with memory (Smith JC et al. 2013).
Now, another study from the same research team suggests that exercise may delay shrinkage of the brain's memory center, which occurs at early stages of Alzheimer's disease.
The brain's memory center: An early victim of Alzheimer's
The hippocampus is a small, seahorse-shaped part of the brain, and plays a key role in memory and spatial orientation.
Shrinkage of the hippocampus is a sign that Alzheimer's disease is progressing … and to a lesser extent, shrinkage also occurs as part of normal aging.
To date, there are no treatments shown to preserve the hippocampus in people at high risk for Alzheimer's disease.
Risk for Alzheimer's is closely tied to the presence of a genetic variation called ApoE4, which also raises the risk for cardiovascular disease.
So news that exercise helps people at high risk for Alzheimer's disease is pretty big news … and it may apply to everyone, since we're at risk of hippocampus shrinkage as we age.
Exercise guarded the hippocampus in people at risk for Alzheimer's
The new study was led by Dr. J. Carson Smith from the University of Maryland School of Public Health, and included scientists from Marquette University, Wayne State University, and the Cleveland Clinic.
Dr. Smith and his colleagues tracked four groups of healthy older adults aged 65-89 with normal cognitive abilities.
They measured the volume of the volunteers' hippocampus using magnetic resonance imaging (MRI) scans at the beginning and end of an 18-month period.
The participants were classified as being at high risk for Alzheimer's if a DNA test identified the presence of a genetic marker – called the APOE-e4 allele – which increases the risk of developing the disease.
Although the majority of people who carry the APOE4 allele show substantial cognitive decline with age and may develop Alzheimer's disease, many do not.
So there's reason to believe that there are other genetic and lifestyle factors at work, including diet, stress, and exercise (Woodard JL et al. 2012).
In addition, the subjects' physical activity levels were measured using a standardized survey.
The participants were then organized into one of four groups:
- Low Alzheimer's risk (those without the ApoE4 gene variation)
- High Alzheimer's risk (those how had the ApoE4 gene variation)
- Low physical activity level - two or fewer days of low intensity activity per week
- High physical activity level - three or more days of moderate to vigorous activity per week
After 18 months, only those at high genetic risk for Alzheimer's who did not exercise showed a drop in the size of their hippocampus (three percent).
All of the other groups – including those at high risk for Alzheimer's who reported high physical activity levels – maintained the volume of their hippocampus.
According to Dr. Kirk Erickson from the University of Pittsburgh, “This is the first study to look at how physical activity may impact the loss of hippocampal volume in people at genetic risk for Alzheimer's disease.”
Importantly, as Dr. Erickson said, “This study has tremendous implications for how we may intervene, prior to the development of any dementia symptoms, in older adults who are at increased genetic risk for Alzheimer's disease.”
Study leader J. Carson Smith summed up his team's findings: “Our study provides additional evidence that exercise plays a protective role against cognitive decline and suggests the need for future research to investigate how physical activity may interact with genetics and decrease Alzheimer's risk.”
“The good news is that being physically active may offer protection from the neuro (brain) degeneration associated with genetic risk for Alzheimer's disease,” Dr. Smith suggested. “Physical activity interventions may be especially potent and important for this group.”
He plans to test the effects of a defined exercise program in healthy older adults with genetic and other risk factors for Alzheimer's disease, to measure their impact on hippocampus volume and brain function.
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