Physical activity, brain tissue microstructure, and cognition in older adults

Area of Science:

• Neuroimaging
• Gerontology
• Cognitive Neuroscience

Background:

• Physical activity is associated with preserved cognition in aging.
• Understanding the biological mechanisms linking physical activity to cognitive function is crucial for public health.
• Postmortem brain analysis offers a unique opportunity to investigate these mechanisms.

Purpose of the Study:

• To determine if postmortem MRI can identify brain tissue characteristics that mediate the relationship between physical activity and cognition in older adults.
• To explore the role of brain microstructure in the physical activity-cognition link.

Main Methods:

• Utilized data from 318 older adults in the Rush Memory and Aging Project.
• Quantified physical activity using wearable devices and assessed cognitive function proximate to death.
• Performed postmortem cerebral MRI to measure transverse relaxation rate (R2) and used spatial independent component analysis (ICA) to analyze R2 maps.
• Employed path analysis to test for mediation by R2 components on the physical activity-cognition association, controlling for motor abilities and brain pathologies.

Main Results:

• Identified two specific R2 components associated with both physical activity and global cognition.
• These R2 components, representing microstructural tissue characteristics in periventricular white matter, hippocampus, and occipital white matter, partially mediated the physical activity-cognition relationship (12.7% of variance).
• The mediation effect persisted after accounting for motor abilities and common brain pathologies.

Conclusions:

• Postmortem MRI-derived signatures of brain tissue microstructure partially explain the association between physical activity and cognitive function in older adults.
• These findings highlight the role of brain tissue integrity in mediating the benefits of physical activity on cognition.
• Further research is warranted to uncover the specific molecular pathways involved.