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Walking Correlates With Brain Volume, Cognitive Ability - published pdf attached
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"DISCUSSION - Brain tissue deteriorates in late adult- hood, but greater amounts of PA have been hypoth- esized to spare brain tissue.2,3,19 In support of this hypothesis, we report that walking greater distances was associated with greater GM volume 9 years later. This effect was significant even after controlling for measures of WM lesions and MRI infarcts at baseline as well as several factors related to general health and disease such as subclinical vascular disease, ventricu- lar grade, and hypertension. The effect was predomi- nant in prefrontal and temporal brain regions including the hippocampus and entorhinal cortex, regions susceptible to age-related deterioration.1 The results of this study establish 3 critical findings. First, greater amounts of PA are predic- tive of greater GM volume 9 years later. Second, walking relatively long distances (72 blocks or roughly 6-9 miles per week depending on the city) was necessary to detect differences in GM 9 years after the baseline evaluation of PA. Third, greater GM in the inferior frontal gyrus, the hippocampus, and the supplementary motor area was associated with a reduced risk of developing cognitive impairment (MCI or dementia)."
MedPage Today
Published: October 14, 2010
Seniors committed to walking had larger gray-matter volume and less cognitive impairment years later than those with more sedentary habits, researchers said.
Among 299 cognitively normal participants in the large Cardiovascular Health Study, those in the top quartile of distance walked each week at baseline had markedly higher gray-matter volumes when measured by MRI nine years later compared with participants in the lower three quartiles, according to Kirk Erickson, PhD, of the University of Pittsburgh, and colleagues.
Action Points
* Note that a large amount of physical activity was necessary to detect a difference in brain structure over a nine-year follow-up period.
* Point out that as an observational study, causality cannot be determined and there remains the possiblity of confounding factors.
Direct correlations between weekly walking distance and the likelihood of later diagnosis with mild cognitive impairment or dementia fell just short of statistical significance (P=0.07), they reported online in the Oct. 19 issue of Neurology.
But they did find significant associations between reduced risk of cognitive impairment and increased volume of three gray-matter regions -- the inferior frontal gyrus (OR 1.99, P<0.01), the hippocampal formation (OR 2.01, P<0.009), and the supplementary motor area (OR 2.24, P<0.01).
"Greater walking distances are associated with greater GM volume in a time period of life in which cortical deterioration and risk for dementia is greatest," the researchers concluded.
The study involved patients in the Pittsburgh component of the multistate Cardiovascular Health Study, a very large longitudinal study designed primarily to examine risk factors for coronary heart disease and stroke.
Out of 1,479 Pittsburgh participants, the current study looked at 299 who were cognitively normal at baseline and had MRI scans after nine years and were assessed clinically for mild cognitive impairment or dementia after 13 years. Mean age at enrollment was 73.
At this final follow-up, 183 still had normal cognition whereas 116 were judged to have some degree of impairment.
Participants were divided into quartiles on the basis of the number of blocks they reported walking each week at baseline. Means for the four quartiles were eight, 21, 45, and 156 blocks, respectively.
Volume of four gray-matter areas was measured in the MRI scans, including the left precentral gyrus, the hippocampus, the precuneus, and the supplementary motor area.
Little difference was seen in volumes of these regions among the three lower quartiles of walking distance, although slight, nonsignificant trends toward greater volume with greater walking distance were apparent.
But the fourth quartile showed clear, significantly greater (P<0.05) volumes in all three areas relative to the other quartiles -- in each case, more than 10% greater.
The effect remained significant after adjusting for age, gender, 15-foot walking speed, body mass index, race, education, skull volume, white matter grade, ventricular grade, and infarcts visible on MRI.
"Because the upper quartile was the only group that demonstrated greater gray matter volume than the other groups, we can assert that a large amount of physical activity is necessary to detect a difference in brain structure over a nine-year follow-up period," Erickson and colleagues wrote.
Limitations to the study included the reliance on self-reports of walking distance, the single measurement of brain volume, lack of full data on comorbidities potentially associated with walking distance, and the exclusion of participants who died during follow-up.
Erickson and colleagues also noted that the study's observational design precluded any conclusions about causality.
The study was funded primarily by the National Institute on Aging, with additional support to individual authors from other NIH institutes and the American Heart Association.
Erickson and most other authors declared they had no financial conflicts of interest. One co-author reported relationships with Pfizer, Eisai, Bristol-Myers Squibb.
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