by Daniel Pendick
Do you get at least 30 minutes of moderate physical exercise
most days of the week? If you did, your brain would appreciate
it. Evidence is mounting that physical activity -- specifically
aerobic exercise -- improves memory and various other brain
functions and may lower the risk of dementia.
Most of the evidence comes from a mountain of studies on rats
and mice, but data collected on people is growing. It shows
convincingly that you can preserve your mental skills as you
age, regain some of the horsepower you’ve already lost,
and even help to stave off Alzheimer’s
disease and other forms of dementia.
“There’s quite a bit of evidence now suggesting
the beneficial effects of moderate intensity exercise on the
brain,” says Kirk Erickson, a neuroscientist at the
University of Pittsburgh. He is at the forefront of research
on exercise and the brain. “This includes maintaining
the structure of the brain and preventing deterioration, but
also improving the actual functioning of the brain as well.”
Even better, you don’t need to run a marathon. You simply
need to engage in some sort of aerobic exercise -- any rhythmic
activity that engages the large muscle groups of the body
-- long enough to raise your heart rate. Think a brisk 45-minute
walk, three or more times per week. Or enough laps in the
pool so that you can feel your pulse thumping. “You
don’t have to be a member of a gym,” Erickson
says. “Primarily we’re measuring people who just
And it’s not too late if you have spent much of your
later years in couch potatohood. Aerobic exercise, even if
started later in life, still improves brain function.
People who are more fit age better in terms of the brain’s
physical condition (structure) and how well it performs mental
tasks (function). And remarkably, it appears that some regions
of the brain important to thinking and memory are actually
larger in fit individuals.
This means people who have remained physically fit as adults
may start out with more “cognitive reserve” as
they enter the second half of life. Statistical studies suggest
these folks are less likely to develop dementia -– or
perhaps they will develop it at a later age than less-fit
Physical activity hits multiple risk factors for memory impairment.
It reduces stress and improves sleep, both of which affect
memory function. Exercise lowers the risk of stroke. And it
helps to control blood sugar, which at high levels can damage
the brain, according to some studies.
Neurobiological studies on rats and mice provide some clues
to the biological details. For example, exercise supports
the growth and survival of new brain cells in the hippocampus,
the pair of seahorse-shaped regions in the brain that play
a central role in memory. Exercise also releases brain chemicals
that may stimulate the growth of blood vessels.
The hippocampus link
In human research, the link between exercise, the hippocampus,
and memory is more recent.
Erickson led a team that has made the connection for the first
time in a study in the October 2009 issue of the journal Hippocampus.
The team performed magnetic
resonance (MR) imaging on about 160 people, aged 59 to
81. They were also assessed for aerobic fitness in a treadmill
test. And they were scored on a task called spatial memory,
or the ability to recall the position of dots flashed on a
The results: The fitter the volunteers were, the better they
performed on the spatial memory test. The MR scans also revealed
a link between hippocampal size and fitness. Statistical analysis
showed that fitness could account for 8 percent of the larger
volume in the right hippocampus and 12 percent in the left.
Statistics also delivered the capping finding of the study:
a “triple association” between aerobic fitness,
hippocampal volume, and spatial memory. That means we can
be more confident in the conclusion that exercise supports
memory by producing a healthy hippocampus.
“This link between exercising and better memory performance
is well known from animal studies,” Erickson says. “But
what are the brain regions involved? This study is really
the first time we’ve been able to put all this together.”
The fitness prescription
So exercise is good for the mind and memory. But Erickson
and other researchers in the field still have some important
gaps to fill. “What is not definitively known is how
much exercise is needed to see these effects," Erickson
says. "Are there any particular types of exercise that
Another important question is how exercise interacts with
other lifestyle factors that influence healthy aging: intellectual
activity, social interaction, and diet. The research can’t
tell us, for example, whether it’s better to go on a
solitary nature walk or join a water aerobics class. The aerobics
class would combine exercise and social interaction. Is there
Asking such questions presents a technical challenge because
it involves measuring the effect of changing two aspects of
a person’s lifestyle. That demands much larger studies
than it takes to measure the effect of exercise alone.
These studies must be done, Erickson says. “It’s
difficult to run just one of them,” he says. “But
people are realizing that these things aren’t independent
of each other. There can be some additional benefit of combining
Factoring in all the influences of lifestyle on cognitive
function might help explain why people age so differently.
“In next few years, we’re going to see more and
more studies trying to combine these factors,” Erickson
The era of larger and more definitive studies on exercise
and the brain is already underway. Erickson is a member of
a team led by psychologist Arthur F. Kramer at the University
of Illinois, Urbana-Champaign, that just completed the largest
study to date. About 150 older adults engaged in supervised
exercise three times per week for a year. Their brains were
scanned before, at 6 months, and after the study.
Erickson says the study is large enough to answer key questions.
“We’ll hopefully get some answers regarding whether
or not starting to exercise when you’re 70 years old
can actually reverse some of the deterioration and cognitive
issues that have arisen.”
If the results are clear and positive enough, they might just
get more people onto the walking path or into the pool. The
prescription for healthy brain aging? Take two laps around
the park and repeat in the morning.
“Aerobic fitness is associated with hippocampal volume
in elderly humans,” by Kirk I. Erickson (Hippocampus,
October 2009, Vol. 19, no. 10, pp. 1030-1039). Abstract
available via PubMed.
“Be smart, exercise your heart: exercise effects on
brain and cognition,” by Charles H. Hillman and others.
(Nature Reviews Neuroscience, 2008, Vol. 9, pp. 58-65.) Abstract
available via PubMed.
“Exercise effects on cognitive and neural plasticity
in older adults,” by Kirk Erickson & Arthur F Kramer
(British Journal of Sports Medicine, published online October
16, 2008.) Abstract
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