Associations between functional capacity, isokinetic leg strength, sleep quality and cognitive function in multiple sclerosis patients: a cross-sectional study.

Objectives: Recent evidence suggests an association between functional capacity and cognitive function, at least in older adults. The aim of this cross-sectional study was to examine the association between cognitive function, functional capacity, isokinetic leg strength, health-related quality of life (HRQOL), sleep quality, body fat, handgrip strength, and fatigue among a sample of MS patients. Methods: Fifty-one relapsing-remitting MS patients (age: 38.4 ± 7.1 yrs; 30 females) were recruited and agreed to participate in this study. Cognitive function was assessed by the Paced Auditory Serial Addition Test (PASAT). Functional capacity was examined using various functional tests commonly used in MS patients. Maximal voluntary unilateral leg strength was assessed using isokinetic dynamometer. Isometric handgrip strength was assessed by a dynamometer. Total body and visceral fat levels were assessed via bioelectrical impedance analyzers. Finally, the patients' HRQOL, sleep quality, and fatigue levels were evaluated using specific questionnaires. Results: A significant association was found between the PASAT score and the performance score in various functional capacity tests (p < 0.050). On the other hand, a weak but statistically significant association was found between the PASAT score and isokinetic strength of knee extensors (r = 0.319, p = 0.022) and knee flexors (r = 0.354 p = 0.011). Poor sleep quality was associated with lower performance in all the functional capacity tests examined (p < 0.05) whilst was negatively associated with the PASAT score (r = -0.334, p = 0.017). The multivariate regression analysis revealed that the performance on the TUG test was a significant predictor of cognitive function. Conclusion: Based on the results of this study, functional capacity was found to be associated with both impaired cognitive performance and low HRQOL in MS patients. In addition, an association between sleep quality and cognitive performance was revealed, confirming existing literature. Functional capacity as assessed by the TUG test emerged as the best predictor of cognitive function.