In 1999, Arthur Kramer, then at the University of Illinois, reported that healthy sedentary people aged 60 to 75 did better on tests requiring executive function if they were assigned to six months of daily walking than if they were assigned to six months of stretching. (Executive function is the ability to plan or make decisions, correct errors, or react to new situations.)
“That was a historic moment because he showed that a behavioral intervention could actually change cognition for an aging individual,” says Laura Baker, associate professor of internal medicine-geriatrics at the Wake Forest University School of Medicine in North Carolina.
“That catapulted many other trials, and it got people to ask whether exercise might be beneficial not only for body function but also for brain health.”
And it led researchers to question whether exercise could help people who were just starting to suffer memory loss.
“I thought, ‘Well, if this is working for healthy older adults, can aerobic exercise have cognitive benefits for someone with a mild cognitive impairment?’” recalls Baker.
In a 2010 study, she assigned 33 people aged 55 to 85 who had mild cognitive impairment to either high-intensity aerobic exercise or stretching. After six months, the women assigned to exercise did better on multiple tests of executive function, while the men improved on only one.
And in a trial of 28 men and women with prediabetes—which is a risk factor for cognitive decline and dementia—aerobic exercise improved executive function, though not memory tests.
“Now we’re doing a study on people with mild cognitive impairment and prediabetes, so these people have a double hit risk for dementia,” notes Baker. “And, so far, we’re seeing the same benefit.”
Her results fit with those from similar studies and with other evidence.
“Most studies find a lower risk of dementia over time for people who exercise or are lifelong exercisers versus those who don’t,” says Baker. “Collectively, this work has set the stage for a new trial that will start in July.”
The study will test 300 sedentary older people with MCI. “It will be a 12-month supervised high-intensity aerobic exercise intervention at ten different sites, and an extra six months where people continue to exercise unsupervised,” explains Baker.
“That’s because we’re trying to see if we can translate the program for community consumption at agencies like the YMCA.”
How might exercise protect the brain?
One target is microscopic blood vessels. “If you’re sedentary, blood doesn’t get to the far reaches of those small vessels,” says Baker. “These are the areas that support the kind of executive function that’s vulnerable to aging. In animals, exercise causes these small vessels to grow and expand their reach.”
Two, exercise may also expand brain volume and, three, protect the endothelial cells that line blood vessels. But why stop there?
“What’s so beautiful about exercise is that it affects insulin (that’s four), blood flow, mood, physiologic stress (that’s five), and more,” says Baker. “Here we have this intervention that affects many different systems that all work together to support brain health.”
Sources: Nature 400: 418, 1999; Arch. Neurol. 67: 71, 2010; J. Alzheimers Dis. 22: 569, 2010; JAMA 300: 1027, 2008; JAMA 292: 1454, 2004.
Other relevant links:
• A recent study shows the importance of physical activity as we age. See: Exercise for Health: Staying Active Can Preserve Mobility in Older Adults
• Strength Training and Memory Loss. See: Exercise for Health: Can Strength Training Boost Your Memory?
• Why sitting is so bad for you. See: Exercise for Health: Sitting May be Worse for You than You Think