Aerobic Exercise Improves Cognitive Functioning of Older Men and Women
DURHAM, N.C. - The team of Duke University Medical Center
researchers who demonstrated in late 1999 that aerobic exercise
is just as effective as medication in treating major depression
in the middle-aged and elderly has now reported that the same
exercise program also appears to improve the cognitive
abilities of these patients.
The researchers found significant improvements in the higher
mental processes of memory and the so-called executive
functions, which include planning, organization and the ability
to mentally juggle different intellectual tasks at the same
time. These improvements were above and beyond what would be
expected after the depression had lifted, the researchers
"What we found so fascinating was that exercise had its
beneficial effect in specific areas of cognitive function that
are rooted in the frontal and pre-frontal regions of the
brain," said James Blumenthal, Duke psychologist and study
principal investigator. Other cognitive functions that were
measured by the team
-- attention, concentration and psychomotor skills
-- did not appear to be affected by the exercise program.
Interestingly, the researchers noted, different regions of the
brain are responsible for these abilities.
The results of the Duke study, funded by a grant from the
National Institute of Mental Health (NIMH), were published in
the January issue of the Journal of Aging and Physical
"The implications are that exercise might be able to offset
some of the mental declines that we often associate with the
aging process," Blumenthal said. "Further studies are warranted
not only to clarify specific mental processes that are improved
by exercise, but to better understand the underlying mechanisms
of these improvements."
While it is unclear why exercise would improve mental
functioning of these patients, Blumenthal believes that it
could be influenced by the improved flow of oxygen-rich blood
to specific regions of the brain.
"We know that in general, exercise improves the heart's
ability to pump blood more effectively, as well as increases
the blood's oxygen-carrying capacity," Blumenthal said. "It is
thought that one of the reasons why the elderly - especially
those with coronary artery disease or hypertension - tend to
suffer some degree of cognitive decline is in part due to a
reduction in blood flow to the brain.
"So it may be that just as exercise improves muscle tone and
function, it may have similar effects on the brain," he
In the original exercise and depression study, dubbed SMILE
(Standard Medical Intervention and Long-term Exercise), the
researchers followed 156 patients between the ages of 50 and 77
who had been diagnosed with major depressive disorder (MDD).
They were randomly assigned to one of three groups: exercise,
medication, or a combination of medication and exercise.
The exercise group spent 30 minutes either riding a
stationary bicycle or walking or jogging three times a week.
The anti-depressant used by the medication group was sertraline
(trade name Zoloft), which is a member of a class of commonly
used anti-depressants known as selective serotonin reuptake
To the surprise of the researchers, after 16 weeks, all
three groups showed statistically significant and identical
improvement in standard measurements of depression, implying
that exercise was just as effective as medication in treating
Not only did study participants take a standard battery of
tests for depression, they took a series of standardized tests
aimed at measuring the cognitive abilities of four separate
domains: memory, executive functioning, attention/concentration
and psychomotor speed. These tests were taken before enrolling
in the trial and four months later.
After comparing the test results from the 42 members of the
exercise group to the 42 members of the medication group, the
researchers found that exercise seemed to have a beneficial
effect on selective areas of cognitive functioning, and that
the level of depression also seemed to play a role.
"The participants with milder depression at the beginning of
the trial were more likely to show an improvement in the
executive functioning domain, while those with moderate to
severe depression showed less improvement," Blumenthal
To better understand this phenomenon, Blumenthal and his
colleagues are now enrolling participants in another
NIMH-funded study, called SMILE-II. Participants must be
clinically depressed, over the age of 50, and must be
physically able to exercise.
The research team included, from Duke, Parinda Khatri,
Michael Babyak, Steve Herman, Teri Baldewicz, David J. Madden,
Dr. Murali Doraiswamy, Dr. Robert Waugh, and Dr. Ranga
Krishnan. Edward Craighead, University of Colorado at Boulder,
was also a member of the team.