Tuesday, October 23, 2012

Getting Physical Ups


Getting Physical Ups Seniors' Brain Volume

By Nancy Walsh, Staff Writer, MedPage Today
Published: October 22, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco
Older individuals who engage in regular physical activity are less likely to experience loss of brain volume and other changes in brain structure, Scottish researchers found.
After adjustment for variables such as age, sex, health, and intelligence, physical activity was significantly associated with less brain atrophy using both computed (standardized β = −0.09, P=0.017) and visually rated (β = −0.08, P=0.044) measures of brain atrophy, according to Alan J. Gow, PhD, of the University of Edinburgh, and colleagues.
In addition, physical activity also was associated with increased gray matter volume (β = 0.09, P=0.038) and a decrease in the computed volume of white matter lesions (β = −0.09, P=0.038), the researchers reported in the Oct. 23 issue of Neurology.
In contrast, they found "no support for a beneficial effect of more intellectually challenging or socially oriented activities, at least in terms of the structural MRI parameters and the time frame considered here," they observed.
It is well recognized that brain structure and function decline with increasing age, and cognitive protective roles have been postulated for physical, mental, and social activities.
However, detailed MRI studies evaluating brain integrity in large populations have been lacking, so Gow and colleagues looked at associations between leisure activities and various MRI findings in the longitudinal Lothian Birth Cohort, which included 700 individuals born in 1936.
At age 70, participants self-reported on their regular activities, and 3 years later they underwent MRI to assess neural tracts, white matter lesions, and atrophy.
Scans included high-resolution T1-weighted sequences, diffusion imaging, and fluid-attenuated inversion recovery-weighted scans.
Mean white matter lesion volume was 7.7 mL, which represented 0.53% of total intracranial volume, the researchers found.
Mean gray matter volume was 34.5% of intracranial volume, while normal-appearing white matter volume was 34.1%.
Mean atrophy in the cohort was 22.4%.
On the Fazekas scale for measuring white matter lesions, including deep and periventricular lesions, the mean score was 2.4.
The researchers performed a series of regression analyses with various covariates, and found that in a model that included age and sex, physical activity was associated with white matter lesions, atrophy, normal-appearing white matter volume, and fractional anisotropy, with higher levels of activity being associated with less atrophy and a smaller lesion load.
Models including other covariates such as social status and childhood intelligence had little effect on the analysis, but the final model revealed the significant associations of physical activity only for atrophy, white matter lesion volume, and gray matter volume.
The researchers also examined the effects of the individual covariates, and found that physical activity, age, and sex were significantly associated with computed atrophy, while age and sex were significant for gray matter volume.
For the white matter lesion Fazekas score, a history of stroke and physical activity both had effects that were independent (β = 0.18, P=0.003 and β = −0.09, P=0.029, respectively).
The sole variable that showed a significant association with nonphysical leisure activities was the volume of normal-appearing white matter (β = 0.10, P=0.010), Gow and colleagues reported.
Further research could be beneficial in elucidating the potential biological mechanisms by which physical activity influences brain microstructure, they noted.
They also pointed out that while physical activity was associated with damage to the white matter, the adjusted model showed no association with normal-appearing white matter.
"This might indicate that any putative protective mechanism works via reducing lesion occurrence, though a detailed examination of physical activity on white matter is required," they cautioned.
Other potential contributors of physical activity to brain integrity may include angiogenesis and upregulation of certain neural chemicals that promote growth.
This study focused specifically on individuals in their early 70s. The lack of an association for nonphysical activities may indicate that these other leisure activities have effects earlier in the aging process, the researchers suggested.
Limitations of the study included its observational design and a lack of information on physical activity at the time of the MRI examinations. Some participants, such as those with declining health, may have altered their activity levels in the 3 years since their initial assessment.
The stdy was funded by a grant from Research Into Aging, the Disconnected Mind project, the Medical Research Council, the Scottish Funding Council, the Biotechnology and Biological Sciences Research Council, the Engineering and Physical Sciences Research Council, and the Economic and Social Research Council.
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