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SUNDAY, July 15 (HealthDay News) — Evidence is mounting that
exercise provides some protection from memory loss and Alzheimer’s
disease, with three new studies showing that a variety of physical
activities are associated with healthier brains in older adults.

One study found that normally sedentary older adults who walked at a
moderate pace three times a week for a year boosted the size of the brain
region involved with memory.

A second study found that twice-weekly resistance (weight) training
helped women with mild signs of mental decline improve their scores on
thinking and memory tests. And the third showed that exercise done for
strength and balance also improved memory.

None of the findings offer a clear-cut prescription for thwarting
mental declines and Alzheimer’s, but taken together, the growing body of
research strongly suggests that physical activity is essential for healthy
brain aging, and may help prevent Alzheimer’s, said Heather Snyder, senior
associate director of medical and scientific relations for the
Alzheimer’s Association.

“These studies really start to strengthen the literature about the
impact that physical activity may have to reduce the risk of Alzheimer’s
disease,” Snyder said.

The studies were to be presented Sunday at the Alzheimer’s Association
annual meeting in Vancouver.

In one study, U.S. researchers at three universities divided 120 older,
sedentary adults without dementia into two groups. One group did aerobic
exercise by walking on a track at a moderate pace for 30 to 45 minutes
three times a week; the other group did stretching and toning
exercises.

A year later, MRI brain scans showed that the size of the hippocampus,
a region of the brain involved with memory, increased by 2 percent in the
walking group. In the stretch-toning group, hippocampal brain volume
declined by 1.5 percent.

After age 50 or 55, adults lose about 1 percent of brain volume per
year, said lead study author Kirk Erickson, an assistant professor of
psychology at the University of Pittsburgh. Marked shrinkage of the
hippocampus can be a sign of Alzheimer’s disease.

The new findings show that “the hippocampus remains very plastic
throughout life, even in late life,” Erickson said. “We can not only stop
it from shrinking, but we can increase the size of the brain in a
relatively short amount of time, just one year of getting people more
active.”

Erickson and his colleagues also measured concentrations in the blood
of brain-derived neurotrophic factor (BDNF), which is important in
learning, memory and other brain functions, Erickson said.

They found that people who had greater increases in the size of their
hippocampus also had a greater boost in BDNF, which suggests a healthier
brain, he said.

Yet, how brain volume or BDNF levels relate to memory or thinking
ability remains murky. The fact that both groups — those who did aerobic
exercise and the stretch-tone group — performed better on thinking and
memory tests after a year says that various types of exercise may act on
different regions of the brain or different brain networks, Erickson said.
Rather than saying one type of exercise is more important than another,
the answer is likely more complex, with various types of physical activity
affecting different aspects of brain health, Erickson said.

To test just that kind of theory, researchers from the University of
British Columbia and the University of Illinois, Urbana, divided 86 women
aged 70 to 80 who already showed signs of mild mental decline into three
groups. One did twice-weekly resistance (weight) training, another did
twice-weekly aerobic training (walking) and the third did twice-weekly
balance and tone exercises.

After six months, the resistance training group showed significantly
improved performance on tests of attention and memory compared to the
other two groups, the researchers found. Resistance training also led to
functional changes in three brain regions involved in memory. The aerobic
training group showed improvement in balance, mobility and cardiovascular
capacity.

The third study, by researchers at the National Center for Geriatrics
and Gerontology in Japan, focused on 47 older adults with the mild memory
impairment who were divided into two groups. One did 90 minutes of
supervised exercise twice a week, while the other, the control group, sat
through a few sessions of health education.

The exercise group did strength training, aerobics and
exercises to improve balance, for one year.

Those in the exercise group showed improvement on a memory task and
tests gauging their ability to use language compared to those in the
education group, although both groups showed memory improvements, the
researchers said.

“There is a lot of evidence out there suggesting that exercises can be
beneficial for you in a whole variety of ways, whether it’s reducing risk
of obesity and weight gain or reducing inflammation,” Erickson said.
“Exercise is associated with an increased lifespan, and repeatedly has
been shown to be associated with reducing risk of dementia. There looks
like there is a very direct link between physical activity and the
integrity of the brain.”

Because this research is being presented at a medical meeting, the data
and conclusions should be viewed as preliminary until published in a
peer-reviewed journal.

In addition, experts noted that while these studies found an
association between exercise and healthier brain aging, the researchers
didn’t prove a cause-and-effect relationship.

More information

The U.S.
National Institute on Aging has more on Alzheimer’s.