How Exercise May Slow Alzheimer's and Dementia
Laura D. Baker, PhD
Neuropsychologist, University of Washington School of Medicine
Memory and Aging
|ADA Research Funding
Henry Becton Innovation Grant
Everyone knows exercise can keep your body healthy. But can it help your brain, too?
Laura Baker thinks the answer is yes. The University of Washington School of Medicine neuropsychologist is particularly interested in exercise's ability to help people with prediabetes and diabetes slow or halt the progression of Alzheimer's and dementia.
The link between dementia and diabetes is particularly important. In a 2004 study of nearly 1,000 older Americans, participants with type 2 diabetes were 65 percent more likely to develop Alzheimer's disease than those without. In fact, "type 2 diabetes is the second most potent risk factor for dementia, other than age," Baker says.
Scientists think type 2 diabetes may create conditions that make the brain more vulnerable. Researchers don't yet understand the details, but they suspect that diabetes damages tiny blood vessels in the brain in much the same way it does in other parts of the body, reducing blood flow and making it easier for Alzheimer's to gain a foothold.
There's also evidence that insulin levels—out of whack in people with prediabetes and diabetes—may play a role. "Insulin has many functions, and one of them is supporting thinking and memory," Baker says. "People with prediabetes and [type 2] diabetes have more insulin in their blood system, but less insulin in their brain."
But Baker thinks that people with prediabetes may be able to halt or even reverse the damage by working out. With the help of a grant from the American Diabetes Association, she has set up an experiment to test the effects of exercise among people with "mild cognitive impairment"—the gray zone between normal brain function and dementia.
The people taking part in Baker's study are between 55 and 85 years old. Before the study begins, participants are given a two-hour set of tests designed to measure their cognition, including exercises to test memory and language skills and the ability to manipulate objects. The scores are compared to tests given all across the nation to see how participants stack up with the population at large. Everyone in the study has some cognitive impairment but has not been diagnosed with dementia, Baker says.
In addition, the participants have prediabetes, a set of conditions including insulin resistance that often lead to type 2 diabetes. Baker seeks out people for whom exercise will make a difference. "Everybody in the study's a couch potato," she says. "They're afraid to exercise and leery about doing something like this."
Baker randomly assigns study participants into one of two groups. Both groups get free gym memberships and meet individually with a trainer four days a week for six months. Half of them are in the "control" group—they do gentle stretching exercises but nothing more. Members of the second group work to get their heart rates up, walking on treadmills or riding stationary bicycles.
At the end of the six months, participants take the same battery of brain tests to see if the exercise had an impact. In two previous studies, Baker has looked at people with prediabetes and mild cognitive impairment, respectively, giving them the same exercise regimen. In both studies, the aerobic-exercise group did markedly better than the group asked just to stretch. "We don't see any benefits in the control group," Baker says. "They're happy and active, but it's not enough."
This latest study might help authoritatively link exercise to better brain function in people with prediabetes. "This might help us look at exercise as if it's a drug," says Baker.
That, in turn, might lead to other changes. If exercise is shown to be as effective as a pill for brain health, for example, maybe insurance plans would start covering gym memberships.
Even more important might be understanding just how closely the body and mind are connected. "We all know we should exercise—we're told to exercise constantly by physicians and the media," Baker points out. "But what's not being said is you need to exercise for your brain. For people who are at risk, hard-core scientific evidence may be what they need to start."
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