Fitness Level Influences White Matter Microstructure in Postmenopausal Women

Abstract

Aerobic exercise has both neuroprotective and neurorehabilitative benefits. However, the underlying mechanisms are not fully understood and need to be investigated, especially in postmenopausal women, who are at increased risk of age-related disorders such as Alzheimer's disease and stroke. To advance our understanding of the potential neurological benefits of aerobic exercise in aging women, we examined anatomical and functional responses that may differentiate women of varying cardiorespiratory fitness using neuroimaging and neurophysiology. A total of 35 healthy postmenopausal women were recruited (59 ± 3 years) and cardiorespiratory fitness estimated (22-70 mL/kg/min). Transcranial magnetic stimulation was used to assess-aminobutyric acid (GABA) and glutamate (Glu) receptor function in the primary motor cortex (M1), and magnetic resonance spectroscopy (MRS) was used to quantify GABA and Glu concentrations in M1. Magnetic resonance imaging was used to assess mean cortical thickness (MCT) of sensorimotor and frontal regions, while the microstructure of sensorimotor and other white matter tracts was evaluated through diffusion tensor imaging. Regression analysis revealed that higher fitness levels were associated with improved microstructure in pre-motor and sensory tracts, and the hippocampal cingulum. Fitness level was not associated with MCT, MRS, or neurophysiology measures. These data indicate that, in postmenopausal women, higher cardiorespiratory fitness is linked with preserved selective white matter microstructure, particularly in areas that influence sensorimotor control and memory.

Aerobic exercise, cardiorespiratory fitness, and the human hippocampus

“…However, the authors reported a trending association between higher cardiorespiratory fitness and lower myelin damage (radial diffusivity) in the right cingulum. Similarly, in postmenopausal women, Harasym et al (2020) found a significant relationship between higher fitness and higher axonal integrity (axial diffusivity) in the hippocampal segments of the cingulum. Bracht et al (2016) found that greater amounts of device‐measured engagement in physical activity was associated with greater myelination (myelin water fraction), but not FA, in the right parahippocampal cingulum in healthy young adults.…”

The Relationship Between Resting Cerebral Blood Flow, Neurometabolites, Cardio-Respiratory Fitness and Aging-Related Cognitive Decline

“…While we observed that VO2max relates positively with GABA+ and Glx when both groups were combined (see Figure 3 ), we did not find any significant relationships when only considering younger and older cohorts separately. Another study in postmenopausal women (age = 59 ± 3 years) also did not find any relationship between VO2max and GABA+ from the motor cortex ( 64 ). From our previous section, we note that Glx plays a critical role in brain functioning and cognition in older participants.…”

The distribution and reliability of TMS-evoked short- and long-latency afferent interactions

“…No correlation was found between age and the depth of SAI, but we did find that SAI was significantly weaker in Study H, which sampled older individuals (59 ± 3 years), than in study A, which sampled a younger cohort (21 ± 2 years). Specifically, Harasym et al [ 22 ] (i.e., study H) studied a group of post-menopausal women while Tsang et al [ 16 ] (i.e., Study A) studied a sample of young males and females. This finding may support a previous meta-analysis reporting a significant decline in SAI with age [ 25 ].…”

“…Data from healthy control participants (n = 170, 73 female) from eight studies that were conducted between 2014 and 2020 in the Neurophysiology and Imaging Laboratory (McMaster University, Hamilton ON, Canada) were included in this retrospective study [14,[16][17][18][19][20][21][22]. Studies and participant demographics are displayed in Table 1.…”