The findings expand upon results of a previous study released last month, which found that walking at least 6 miles per week helped to preserve brain size and prevent the onset of dementia in healthy adults.
"Physical activity boosts the brain's resistance to Alzheimer's," said lead study author Cyrus Raji, PhD, from the university's department of radiology. "People who walked more had a slower progression of Alzheimer's disease and mild cognitive impairment over five years, and, as a result, they had a better preservation of the hippocampus, the frontal lobes, and the temporal lobes."
Patients were recruited from the Cardiovascular Health Study - Cognition Study (CHS-CS), which began approximately 20 years ago to explore coronary heart disease and stroke in people ages 65 and older.
Physical activity
Raji and colleagues analyzed the relationship between physical activity and brain structure in 426 people, including 299 healthy adults (mean age, 78 years) and 127 cognitively impaired adults (mean age, 81 years). Among the 127 cognitively impaired adults, 83 people had mild cognitive impairment and 44 adults had Alzheimer's dementia.
"Mild cognitive impairment is believed to be a very early presentation of dementia with symptoms that are not as advanced as Alzheimer's," Raji said. "As many as 50% of the people who have mild cognitive impairment go on to develop Alzheimer's."
In addition to the MRI scans, patients were given the mini-mental state exam (MMSE) to track cognitive decline over five years. Physical activity levels were correlated with MRI and MMSE results. The analysis adjusted for age, gender, body fat composition, head size, education, and other factors.
Among those who began the study as normal and eventually developed Alzheimer's and mild cognitive impairment over 10 years, the people who walked 5 miles per week -- a little less than 1 mile per day -- had similar preservation of brain volume compared to people who remained healthy longer.
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Alzheimer's progression
"What excites me the most is that individuals who walked 5 miles per week and developed mild cognitive impairment and Alzheimer's disease did not lose as much brain tissue over time," Raji said. "So the people who walked more had a slower progression of Alzheimer's disease and mild cognitive impairment and, as a result, they had a better preservation of the hippocampus, the frontal lobes, and the temporal lobes."
Another significant finding came from the longitudinal MMSE test results. "In the people who developed Alzheimer's disease and walked 5 miles per week, their MMSE scores went down only one point over 10 years," Raji said. "With sedentary individuals who developed Alzheimer's, their scores went down five points over 10 years."
These findings persisted even after adjusting for factors such as age, gender, race, education, and stroke. The researchers directly attributed the improvement in memory loss to the preserved hippocampal volume from walking.
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Raji and his colleagues plan to continue their research of what factors contribute to Alzheimer's and mild cognitive impairment by looking at diet.
"A lot of research is being done to determine if fish oil, for example, can have a beneficial effect in preventing Alzheimer's disease or reducing the risk," he said. "There have been studies done in the past suggesting that fish oil, which helps make up the building blocks of cell membranes and helps with cholesterol metabolism, might have other beneficial effects on the brain as well."
By Wayne Forrest
image 1 :The images compare the beneficial effects of physical activity on the brains of 299 healthy aging individuals to the positive relationships between exercise and brain structure in 127 people with either mild cognitive impairment or Alzheimer's. In both normal aging and cognitive impairment, physical activity preserves volume in brain areas that are important for memory, learning, and attention. These structures include the prefrontal cortex and temporal cortex. The top row of images shows these relationships in a 3D rendering of the brain, while the bottom row shows the prefrontal cortex findings in side view cutaway images of the brain.
image 2 :Side-view cutaway images show the sparing of brain volume in 299 healthy aging people (left) and 127 individuals with cognitive impairment and Alzheimer's (right). In both groups, there is more frontal lobe volume with walking about 1 mile per day, which translates to a reduced risk for cognitive impairment in the healthy aging group and slower decline in the cognitively impaired group.
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