Associations between physical fitness and structural and functional MRI measures in secondary progressive multiple sclerosis: Cross-sectional findings from the exercise PRO-MS study.

OBJECTIVE

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

METHODS

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.

RESULTS

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).

CONCLUSION

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.