A study of older adults at increased risk
for Alzheimer's disease shows that moderate physical activity may protect brain
health and stave off shrinkage of the hippocampus – the brain region
responsible for memory and spatial orientation that is attacked first in
Alzheimer's disease. Dr. J. Carson Smith, a kinesiology researcher
in the University of Maryland School of
Public Health who conducted the study, says that while all of us
will lose some brain volume as we age, those with an increased genetic risk for
Alzheimer's disease typically show greater hippocampal atrophy over time. The
findings are published in the open-access journal Frontiers in
Aging Neuroscience.
"The good news is that being
physically active may offer protection from the neurodegeneration associated
with genetic risk for Alzheimer's disease," Dr. Smith suggests. "We
found that physical activity has the potential to preserve the volume of the
hippocampus in those with increased risk for Alzheimer's disease, which means
we can possibly delay cognitive decline and the onset of dementia symptoms in these
individuals. Physical activity interventions may be especially potent and
important for this group."
Dr. Smith and colleagues, including Dr.
Stephen Rao from the Cleveland Clinic, tracked four groups of healthy older
adults ages 65-89, who had normal cognitive abilities, over an 18-month period
and measured the volume of their hippocampus (using structural magnetic
resonance imaging, or MRI) at the beginning and end of that time period. The
groups were classified both for low or high Alzheimer's risk (based on the
absence or presence of the apolipoprotein E epsilon 4 allele) and for low or
high physical activity levels.
Of all four groups studied, only those at
high genetic risk for Alzheimer's who did not exercise experienced a decrease
in hippocampal volume (3 percent) over the 18-month period. All other groups,
including those at high risk for Alzheimer's but who were physically active,
maintained the volume of their hippocampus.
"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," says Dr. Kirk Erickson, an
associate professor of psychology at the University of Pittsburgh. "There
are no other treatments shown to preserve hippocampal volume in those that may
develop Alzheimer's disease. 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."
Individuals were classified as high risk
for Alzheimer's if a DNA test identified the presence of a genetic marker –
having one or both of the apolipoprotein E-epsilon 4 allele (APOE-e4 allele) on
chromosome 19 – which increases the risk of developing the disease. Physical
activity levels were measured using a standardized survey, with low activity
being two or fewer days/week of low intensity activity, and high activity being
three or more days/week of moderate to vigorous activity.
"We know that the majority of people
who carry the E4 allele will show substantial cognitive decline with age and
may develop Alzheimer's disease, but many will not. So, there is reason to
believe that there are other genetic and lifestyle factors at work," Dr.
Smith says. "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."
Dr.
Smith has
previously shown that a walking exercise intervention for patients
with mild cognitive decline improved cognitive function by improving the
efficiency of brain activity associated with memory. He is planning to conduct
a prescribed exercise intervention in a population of healthy older adults with
genetic and other risk factors for Alzheimer's disease and to measure the
impact on hippocampal volume and brain function.
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