Association between cardiorespiratory fitness and total brain myelin volume among older adults

Abstract

Background: Myelin, which insulates neurons, speeds up information transfer and provides the necessary conditions for cognitive and motor functioning. The direct link between physical performance and the total brain myelin volume remains unclear.

Methods: This study involved 87 healthy participants (71 women, 16 men) with a mean age of 69.3 ± 3.14 years and a mean body mass index of 27.83 ± 3.93 kg/m². Several measures of physical fitness (isometric muscle strength, handgrip strength, and cardiopulmonary exercise testing) were examined for their correlations with the total brain myelin volume using Synthetic MRI, an FDA-approved myelin assessment software.

Results: A high maximal respiratory exchange ratio and low maximal heart rate achieved during cardiopulmonary exercise testing were associated with higher estimated brain myelin content. In addition, the handgrip strength test performance as well as the peak and average peak torque were associated with higher brain parenchymal myelin volumes.

Conclusions: We demonstrated that higher brain myelin content was positively associated with better cardiorespiratory fitness and higher upper and lower limb muscle strength in older individuals. These findings provide new insights into the development of improved rehabilitation and exercise schemes to preserve cognitive health in the older adult population.

Keywords: Human brain; Magnetic resonance imaging; Myelin; Physical activity.

Fig. 1

Association between myelin compound and cardiorespiratory fitness. (a) RER_max vs. MYC/ICV, (b) RER_max vs. MYC/BPV (c) HR_max vs. MYC/ICV, (d) HR_max vs. MYC/BVP. Both, the proportions of myelin relative to intracranial volume and brain parenchymal volume MyC/ICV and MyC/BPV show a consistent moderate positive correlation with the respiratory exchange ratio (RER_max) and a negative correlation with maximal heart rate (HR_max)