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Poor Fitness Linked to Weaker Brain Fiber and Higher Risk of Dementia

Summary: UT Southwestern researchers shed light on the link between poor fitness and an increased risk of developing dementia. Researchers report a lower level of fitness is associated with faster deterioration of white matter fibers in the brain. The deterioration can result in cognitive decline and memory problems as a person ages.

Source: UT Southwestern.

Scientists have more evidence that exercise improves brain health and could be a lifesaving ingredient that prevents Alzheimer’s disease.

In particular, a new study from UT Southwestern’s O’Donnell Brain Institute suggests that the lower the fitness level, the faster the deterioration of vital nerve fibers in the brain. This deterioration results in cognitive decline, including memory issues characteristic of dementia patients.

“This research supports the hypothesis that improving people’s fitness may improve their brain health and slow down the aging process,” said Dr. Kan Ding, a neurologist from the Peter O’Donnell Jr. Brain Institute who authored the study.

White matter

The study published in the Journal of Alzheimer’s Disease focused on a type of brain tissue called white matter, which is comprised of millions of bundles of nerve fibers used by neurons to communicate across the brain.

Dr. Ding’s team enrolled older patients at high risk to develop Alzheimer’s disease who have early signs of memory loss, or mild cognitive impairment (MCI). The researchers determined that lower fitness levels were associated with weaker white matter, which in turn correlated with lower brain function.

Distinctive tactics

Unlike previous studies that relied on study participants to assess their own fitness, the new research objectively measured cardiorespiratory fitness with a scientific formula called maximal oxygen uptake. Scientists also used brain imaging to measure the functionality of each patient’s white matter.

Patients were then given memory and other cognitive tests to measure brain function, allowing scientists to establish strong correlations between exercise, brain health, and cognition.

Lingering mysteries

The study adds to a growing body of evidence pointing to a simple yet crucial mandate for human health: Exercise regularly.

However, the study leaves plenty of unanswered questions about how fitness and Alzheimer’s disease are intertwined. For instance, what fitness level is needed to notably reduce the risk of dementia? Is it too late to intervene when patients begin showing symptoms?

Some of these topics are already being researched through a five-year national clinical trial led by the O’Donnell Brain Institute.

The trial, which includes six medical centers across the country, aims to determine whether regular aerobic exercise and taking specific medications to reduce high blood pressure and cholesterol levels can help preserve brain function. It involves more than 600 older adults at high risk to develop Alzheimer’s disease.

“Evidence suggests that what is bad for your heart is bad for your brain. We need studies like this to find out how the two are intertwined and hopefully find the right formula to help prevent Alzheimer’s disease,” said Dr. Rong Zhang of UT Southwestern, who oversees the clinical trial and is Director of the Cerebrovascular Laboratory in the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital Dallas, where the Dallas arm of the study is being carried out.

Prior findings

The research builds upon prior investigations linking healthy lifestyles to better brain function, including a 2013 study from Dr. Zhang’s team that found neuronal messages are more efficiently relayed in the brains of older adults who exercise.

brain scans

Brain imaging shows yellow and reddish pixels representing areas where the functionality of white matter is associated with higher fitness levels. The images are based on cumulative data from patients in a study showing potential links between physical fitness and deterioration of white matter. NeuroscienceNews.com image is credited to UT Southwestern Medical Center.

In addition, other teams at the O’Donnell Brain Institute are designing tests for the early detection of patients who will develop dementia, and seeking methods to slow or stop the spread of toxic proteins associated with the disease such as beta-amyloid and tau, which are blamed for destroying certain groups of neurons in the brain.

“A lot of work remains to better understand and treat dementia,” said Dr. Ding, Assistant Professor of Neurology & Neurotherapeutics. “But, eventually, the hope is that our studies will convince people to exercise more.”

About this neuroscience research article

Funding: The study was supported in part by the National Institutes of Health and the American Heart Association. It included collaborations with staff at the Institute for Exercise and Environmental Medicine and UT Southwestern’s Alzheimer’s Disease Center. Dr. Zhang is Professor of Neurology & Neurotherapeutics and Internal Medicine at UT Southwestern.

Source: James Beltran – UT Southwestern
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is credited to UT Southwestern Medical Center.
Original Research: Abstract in Journal of Alzheimer’s Disease.
doi:10.3233/JAD-170415

Cite This NeuroscienceNews.com Article
UT Southwestern “Poor Fitness Linked to Weaker Brain Fiber and Higher Risk of Dementia.” NeuroscienceNews. NeuroscienceNews, 15 February 2018.
<http://neurosciencenews.com/dementia-fitness-brain-fiber-8497/>.
UT Southwestern (2018, February 15). Poor Fitness Linked to Weaker Brain Fiber and Higher Risk of Dementia. NeuroscienceNews. Retrieved February 15, 2018 from http://neurosciencenews.com/dementia-fitness-brain-fiber-8497/
UT Southwestern “Poor Fitness Linked to Weaker Brain Fiber and Higher Risk of Dementia.” http://neurosciencenews.com/dementia-fitness-brain-fiber-8497/ (accessed February 15, 2018).

Abstract

Cardiorespiratory Fitness and White Matter Neuronal Fiber Integrity in Mild Cognitive Impairment

Background: Mounting evidence showed the self-reported levels of physical activity are positively associated with white matter (WM) integrity and cognitive performance in normal adults and patients with mild cognitive impairment (MCI). However, the objective measure of cardiorespiratory fitness (CRF) was not used in these studies.

Objective: To determine the associations of CRF measured by maximal oxygen uptake (VO2max) with WM fiber integrity and neurocognitive performance in older adults with MCI. Methods:Eighty-one participants (age = 65±7 years, 43 women), including 26 cognitively normal older adults and 55 amnestic MCI patients, underwent VO2max test to measure CRF, diffusion tensor imaging (DTI) to assess WM fiber integrity, and neurocognitive assessment focused on memory and executive function. DTI data were analyzed by the tract-based spatial statistics and region-of-interest approach.

Results: Cognitively normal older adults and MCI patients were not different in global WM fiber integrity and VO2max. VO2max was associated positively with DTI metrics of fractional anisotropy in ∼54% WM fiber tracts, and negatively with mean and radial diffusivities in ∼46% and ∼56% of the WM fiber tracts. The associations of VO2max with DTI metrics remained statistically significant after adjustment of age, sex, body mass index, WM lesion burden, and MCI status. The DTI metrics obtained from the area that correlated to VO2max were associated with executive function performance in MCI patients.

Conclusions: Higher levels of CRF are associated with better WM fiber integrity, which in turn is correlated with better executive function performance in MCI patients.

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