Frank Himmel, 81, works out for heart health in a cardiac rehabilitation program at Providence St. Vincent Medical Center. A new study shows that aerobic training also helps the brain's mental agility.
There is no proven way to prevent Alzheimer's disease, but a new Seattle-area study provides some of the strongest evidence yet that regular exercise can protect the brain -- and even improve cognitive performance -- in older adults showing signs of mental decline.
Researchers at the University of Washington School of Medicine and Veterans Affairs Puget Sound Health Care System tested the effects of aerobic training in a clinical trial with 33 women and men diagnosed with mild cognitive impairment, often a prelude to Alzheimer's disease.
Twenty-three of the volunteers, selected randomly, began an intense program of aerobic exercise, spending 45 to 60 minutes on a treadmill or stationary bike four days a week. The remaining 10, the study's control group, spent the same amount of time performing non-aerobic stretching and balance exercises. After six months, the aerobic exercisers showed significant gains in mental agility, while the non-aerobic group showed continuing decline in tests of thinking speed, fluency with words and ability to multi-task.
While it remains unknown whether fitness training can prevent Alzheimer's, many scientists firmly believe it is more likely to help than existing pharmaceuticals or supplements, which have failed to show preventive effects in clinical trials.
"We know some level of exercise is critical, we just don't know how much is needed," said Laura Baker, a research scientist at the Puget Sound VA, assistant professor at UW, and lead author of
published Monday in Archives of Neurology.
Previous studies have linked exercise and brain resilience, but much of the evidence has been circumstantial or based on animal rather than human experiments. The Seattle study, funded by the Alzheimer's Association and the Department of Veterans Affairs, is one of the first randomized clinical trials showing that exercise is a source of brain protection, said Dr. Jeffrey Kaye, director of the Layton Aging and Alzheimer's Disease Center at Oregon Health & Science University, who was not involved in the study.
"The bottom line is, movement and activity does really seem to be good for your brain," Kaye said. The challenge now, he said, "is to understand, at a scientific level, what elements of activity really do enhance brain function, and what level, what dose of activity is needed."
Kaye said he and other researchers, including Baker's group in Seattle, are planning a larger, longer clinical trial. By following volunteers for years instead of months, Kaye said it might be possible to learn whether exercise can prevent full-blown Alzheimer's disease. Researchers expect to apply for federal funding this year.
Scientists don't fully understand
, scrambles the ability to think and erodes personality. Nerve cells die and the brain shrivels as the disease advances. The damage seems to begin with the clustering of protein fragments, called amyloid plaques, among brain cells. Larger, tangled strands of another protein soon appear inside brain cells. Generally, the more plaques and tangles, the more severe the symptoms of dementia.
Because lifestyle factors seem to lower the risk, some researchers suspect that physical fitness, overall health and mental stimulation provide a buffer, or reserve, that allows the brain to withstand more damage and still function normally. Strong social connections also seem to help, perhaps by ameliorating stress.
It's clear that uncontrolled high blood pressure and diabetes contribute to the loss of brain cells. High blood pressure destroys small blood vessels that bring oxygen and nutrients to brain cells. Diabetes, in which the body loses control of energy metabolism, worsens blood pressure and artery damage.
Aerobic exercise probably protects the brain in several ways, Baker said. It builds heart and artery resilience, which boosts blood flow to the brain. Exercise keeps energy metabolism stable, preventing and even reversing diabetes. Exercise also relieves stress, preventing damaging chain-reactions unleashed by the build-up of stress hormones.
Dr. Michael Mega, a neurologist and neuroscientist with the Providence Brain Institute in Portland, said the Seattle study fits with the emerging view that heart health and brain health go hand in hand.
"All of the things that cause your heart to stop working well -- sedentary lifestyle, high cholesterol, diabetes, smoking -- are also the risk factors that come right underneath advanced age as factors increasing risk for Alzheimer's disease," Mega said.
Mega found one result jarring in the new study: exercise didn't improve performance on memory tests. In a previous study, a moderate exercise program -- brisk walking -- improved memory after one year in Dutch women and men with mild cognitive impairment. Kaye said memory gains may take longer than six months to emerge or require a different type or intensity of exercise than used in the Seattle study.
For reasons that remain unclear, aerobic training helped women's mental agility substantially more than it helped men's. "It might be that this was the perfect dose of exercise for women but not men," said Baker, the study author.
But people who aren't exercising regularly shouldn't wait for more scientific data to get going, Baker said. "Don't worry about the intensity. You can start by walking 20 minutes a day," she said.
"Just get moving. You don't need to join a gym or hire a personal trainer."
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