Fitness Linked to Brain White Matter Integrity in Aging

Cardiovascular fitness has been correlated with a variety of beneficial effects on brain structure and cognition.

These correlations have not proven causality but they do support continued imaging and brain function studies.

Scott Hayes from the VA Boston Healthcare System and Boston School of Medicine recently published an information study on this topic.

Brain white matter integrity is now open for study using diffusion tensor imaging, available from high-resolution magnetic resonance imaging (MRI).

In the current study, the research team used the following key elements in their study design:

• Subjects: 34 younger adults between 18-31 years of age and 33 older adults between 55-82 years of age free of significant medical, neurological illness without a history of traumatic brain injury.
• Fitness Testing Protocol: All subjects completed cardiopulmonary exercise testing via treadmill testing to determine fitness levels via an estimation of peak oxygen consumption.
• Imaging Protocol: Brain MRI using 3 Tesla Siemens scanner
• Statistical Analysis: Measures of white matter integrity were compared between younger and older age groups. Additionally, peak VO2 was used as a covariate interaction term.

The research team found some interesting results including the following: 

1. Older age contributed significantly to measures of impairment in white matter microstructure across a wide anatomical distribution of the white matter tracts

2. Older adults with higher level fitness estimates had higher measures of white matter integrity approaching that seen in younger adults in the following brain regions:

• splenium
• sagittal stratum
• posterior corona radiata
• superior parietal lobe

3. Fitness levels in young adults were not correlated to measures of white matter

The positive association of better white matter integrity with higher levels of cardiovasular fitness seemed to occur at about the 75th percentile performance for VO2 by age. The older age high fitness group in this study had a mean estimated peak VO2 of 37.0 ml/kg per min compared to 23.7 in the low fitness older group.

The authors note that fitness in older men has significant brain benefits but cannot completely eliminate the effects of brain aging on white matter integrity. Some regions appear more benefited by higher fitness levels than others.

A key limitation of the current study is the cross-sectional design. The cross-sectional design limits causality interpretation between fitness and brain aging. It is possible a genetic or other factor contributes to both fitness and brain aging.

This study does not inform on the potential benefits of an exercise intervention to increase VO2 on white matter integrity.

Additionally, it does not inform on the potential of using fitness exercise to prevent or reduce the cognitive impairment linked to degenerative diseases such as Alzheimer's disease. 

Nevertheless, this study does add to the growing evidence of a link between exercise and brain health. A positive effect on the brain white matter integrity may be a key component of this association.

Readers with more interest in this study can access the free full-text manuscript by clicking on the citation link below.

Image of corona radiata (posterior region area linked to improved integrity with higher fitness levels in current study) is a screen shot from the iPad app Brain Tutor.

Follow the author on Twitter at WRY999

Hayes SM, Salat DH, Forman DE, Sperling RA, & Verfaellie M (2015). Cardiorespiratory fitness is associated with white matter integrity in aging. Annals of clinical and translational neurology, 2 (6), 688-98 PMID: 26125043