Associations between physical fitness and structural and functional MRI measures in secondary progressive multiple...

To explore the associations between physical fitness and brain MRI-measures in people with secondary progressive MS (SPMS).

We assessed associations between physical fitness (i.e., cardiorespiratory fitness, leg muscle strength, and self-reported level of physical activity) and MRI-derived measures (i.e., brain volume, and resting-state functional (rsFC) of the default-mode network with the rest of the brain (DMN-brain) and sensorimotor network with the rest of the brain (SMN-brain)) using multiple linear regression analyses. Physical fitness was compared to published reference data, and MRI measures were compared to reference MRI data from healthy controls (HC) from Amsterdam UMC.

Twenty-nine participants with SPMS (median age 54 years (IQR:48-61), 69 % female) demonstrated lower physical fitness compared to published reference values, and reduced brain volume and rsFC of the SMN-brain compared to HC (n = 28, median age 54 (IQR:44-61, 64 % females). None of the associations between physical fitness and brain measures reached statistical significance (Bonferroni-adjusted). We observed two trends suggesting associations between: [1] better cardiorespiratory fitness and higher rsFC of the SMN-brain (b = 18,139.7, 95 %CI:86.4; 36,193.1), and [2] between higher self-reported level of physical activity and higher rsFC of the DMN-brain (b = 1810.2, 95 %CI:189.8; 3430.7).

In our cohort of 29 people with SPMS, no statistically significant associations were found between physical fitness and brain volumetric measures. A potential tendency towards associations were observed between better cardiorespiratory fitness and higher rsFC of the SMN-brain and higher self-reported level of physical activity and higher rsFC of the DMN-brain, suggesting a potential effect of physical fitness on functional brain connectivity in SPMS.