Based on a review of studies on exercise and
its effect on brain functioning in human and animal
populations, researchers find that physical exercise
may slow aging's effects and help people maintain
cognitive abilities well into older age.
Animals seem to benefit from exercise too and
perform spatial tasks better when they are active.
Furthermore, fitness training – an increased level
of exercise – may improve some mental processes
even more than moderate activity, say the authors
of the review.
Findings from the review will be presented at
the 114th Annual Convention of the American Psychological
Association (APA).
Varying opinions still exist on the benefits
of exercise and activity, said authors Arthur
F. Kramer, PhD, Kirk I. Erickson, PhD and Stanley
J. Colcombe of the University of Illinois at Urbana
– Champaign, "but our review of the last 40 years
of research does offer evidence that physical
exercise can have
a positive influence on cognitive and brain functions
in older animal and human subjects." Different
methodologies were examined to comprehensively
study what effects exercise can have.
The researchers first examined the epidemiological
literature of diseases to determine whether exercise
and physical activity can at certain points in
a person's lifetime improve cognitive ability
and decrease the likelihood of age-related neurological
diseases, like Alzheimer's. The authors then reviewed
longitudinal randomized trial studies to see if
specific fitness training had an affect on cognition
and brain function in older adults. Finally, animal
studies were examined to understand the molecular
and cellular mechanisms responsible for exercise
effects on the brain as well as on learning and
memory.
Based on a review of the epidemiological literature,
the authors found a significant relationship between
physical activity and later cognitive function
and decreased occurrence of dementia. And the
benefits may last several decades. In a few of
the studies that examined men and women over 65
years old, the findings showed that those who
exercised for at least 15-30 minutes at a time
three times a week were less likely to develop
Alzheimer's Disease, even if they were genetically
predisposed to the disease.
By examining the human intervention studies,
a relationship was also found between fitness
training and improved cognition, more efficient
brain function and retained brain volume in older
people, said Kramer. He cautions that different
fitness training regimens and aspects of mental
functions need further study to solidify a causal
relationship. But, he added, there are some preliminary
positive findings. In a four year study looking
at the relationship between physical activity
on cognition and brain function in 62-70 year
olds, "those who continued to work and retirees
who exercised showed sustained levels of cerebral
blood flow and superior performance on general
measures of cognition as compared to the group
of inactive retirees," said Kramer.
Other studies confirmed the evidence that fitness
does have positive effects on brain function in
older adults. A study of older adults who were
randomly assigned to either a walking group or
a stretching and toning control group for six
months found that those in the walking group were
better able to ignore distracting information
in a distractibility task than those in the control
group. "Aerobically trained older adults showed
increased neural activities in certain parts of
the brain that involved attention and reduced
activity in other parts of the brain that are
sensitive to behavioral conflict," said Kramer.
Animal studies also provide support for the aging
benefits of physical activity. Analyzing the effects
of exercise in animal populations provides a unique
window into learning about exercise-induced neurological
and cognitive plasticity – the ability of parts
of the brain to function in place of other parts
of the brain, said Dr. Kramer. Some of the animal
studies reviewed used voluntary-wheel running
experiments to show the existence of performance
benefits of wheel running on hippocampus-related
spatial learning tasks. Moreover, a few studies
found that aged rodents that exercised in a water
maze learned and retained information about a
hidden platform better than age-matched controls.
Exercise also protected both young and aged animals
from developing some age-related diseases as indicated
by increases in certain neurochemical levels that
can offset or prevent certain pathological diseases.
"From this review we have found that physical
and aerobic exercise training can lower the risk
for developing some undesirable age-related changes
in cognitive and brain functions," said Dr. Kramer,
"and also help the brain maintain its plasticity
- ability to cover one function if another starts
failing later in life."
More research is needed to know exactly how much
and what types of exercise produce the most rapid
and significant effects on thinking and the brain;
how long exercise effects last following the end
of training; or how much exercise is needed to
get continued benefits, said Kramer.
