Dr. Erickson admitted he was quite astonished at their findings. "Other studies have previously shown that exercise is related to brain function," he said, "but the fact that we found that walking as little as 1 mile a day is related to brain volume 9 years later, and dementia 13 years later, is truly novel and really quite impressive," he said.
Age-Related Loss of Brain Volume
According to the researchers, the volume of gray matter shrinks in late adulthood and often precedes cognitive impairment. Participation in physical activity and exercise has been "hypothesized to protect against the deterioration of brain tissue, but this hypothesis has not been tested in longitudinal studies," Dr. Erickson and colleagues write.THE STUDY
In this study, 299 dementia-free people (mean age, 78 years) from the Cardiovascular Health Cognition Study were assessed for physical activity, as measured by the number of blocks they walked in 1 week. Nine years after the physical activity assessment, magnetic resonance imaging (MRI) scans were used to measure brain size. Four years later, the participants were tested for cognitive impairment and dementia.
Participants were classified into 4 quartiles based on the number of blocks walked, and MRI measurement 9 years later ascertained that gray matter volume in the highest quartile differed from the other 3 quartiles (all P < .05).
RESULTS
Participants who walked at least 72 blocks — approximately 6 to 9 miles — per week had more gray matter than people who walked less; however, walking more than 72 blocks did not appear to increase gray matter volume any further.
Areas of the brain with an increase in volume associated with a reduced risk of developing cognitive impairment were the inferior frontal gyrus, hippocampal formation, and supplementary motor area.
FOUR YEAR FOLLOW-UP
In the 4-year follow-up, 116 of the participants, or 40%, had developed cognitive impairment or dementia. Greater gray matter volume with physical activity was associated with a 2-fold reduced risk for cognitive impairment. "Based on our results, we can conclude that there is a relation between the amount of walking earlier in life and brain volume in later adulthood and that greater volume of tissue related to walking is associated with a reduced risk of cognitive impairment," the study authors suggest.
THE FUTURE
Dr. Erickson added that much more work is needed from randomized trials that assign people to an exercise treatment for long periods. "Only under these conditions will we be able to determine the extent to which exercise augments brain function in late life," he said.
LESSONS FOR US ALL
The new research study concludes one thing: walking at least 6 miles per week appears to maintain brain volume and preserve memory in old age.
In regard to these results, the findings are exciting because they suggest an association between physical activity in the form of walking, with brain structure, and dementia across the period of a decade.
Such results provide yet another reason for the medical community to prescribe physical activity as means to reduce the probability of age-associated neurodegenerative disease.
Related: What is Dementia?
Reference:
1). K.I. Erickson, PhD,* C.A. Raji, PhD,* O.L. Lopez, MD et al. Physical activity predicts gray matter volume in late adulthood: The Cardiovascular Health Study. Neurology. 2010;75:1415-1422. [PMC free article]
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