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Supplemental material, Supplementary_data_table_1_manuscript_test-retest_reliability_of_CMI-assessments_in_pwMS for Test-Retest Reliability of Cognitive-Motor Interference Assessments in Walking With Various Task Complexities in Persons With Multiple Sclerosis by Renee Veldkamp, Anders Romberg, Paivi Hämäläinen, Xavier Giffroy, Lousin Moumdjian, Carmela Leone, Peter Feys and Ilse Baert in Neurorehabilitation and Neural Repair

Background. Simultaneous execution of motor and cognitive tasks can result in worsened performance on one or both tasks, indicating cognitive-motor interference (CMI). A growing amount of research on CMI in persons with multiple sclerosis (pwMS) is observed. However, psychometric properties of dual-task outcomes have been scarcely reported. Objective. To investigate the between-day test-retest reliability of the motor and cognitive dual-task costs (DTCs) during multiple CMI test conditions with various task complexities in pwMS and matched healthy controls (HCs). Methods. A total of 34 pwMS (Expanded Disability Status Scale score 3.0 ± 0.8) and 31 HCs were tested and retested on 3 single cognitive, 4 single motor, and 12 cognitive-motor dual tasks. Cognitive tasks included serial subtraction by 7, titrated digit span backward, and auditory vigilance. Motor tasks were walking at self-selected speed, over obstacles, crisscross, and while carrying a water-filled cup. Outcome measures were cognitive and motor DTC, calculated as percentage change of dual-task performance compared with single-task performance. Intraclass correlations (ICCs) and Spearman correlation coefficients were calculated as appropriate. Results. For DTCmotor of gait speed, ICCs ranged from 0.45 to 0.81 and Spearman correlations from 0.74 to 0.82. For DTCcognitive, ICCs ranged from −0.18 to 0.49 and Spearman correlations from −0.28 to 0.26. Reliability depended on the type of motor and cognitive task. Conclusion. Reliability of the DTCmotor was, overall, good, whereas that of the DTCcognitive was poor. The “walking” and “cup” dual-task conditions were the most reliable regardless of the integrated cognitive task. The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The study was supported by RIMS by Novartis AG, MS Society Flanders, Swedish Promobilia Foundation, and SailingChallenge4MS.

People with multiple sclerosis (MS) suffer from motor and cognitive impairments. In recent years, some studies investigated the impact of performing both cognitive and motor task simultaneously compared to singular. A decreased velocity by taking fewer and shorter steps was found. So far, cognitive-motor testing was mostly only executed once, with a current lack of knowledge on its reliability limiting its use as an experimental outcome measure. For this reason, we wanted to investigate the between-day reliability of dual task costs (on cognition and mobility) during diverse cognitive-motor interference test conditions in 22 persons with MS (pwMS) and 22 age-gender matched healthy controls. Cognitive tasks were: counting backwards by seven, titrated digit span backwards and auditory vigilance with alphabet. Motor tasks were: walking at a self-selected speed, walking while stepping over low obstacles, walking crisscross and walking while carrying a cup filled with water. Experimental outcome measure was the cognitive-motor interference (CMI), expressed in cognitive, motor and combined dual task cost (DTC). Reliability of the motor DTC was better than cognitive DTC. The most reliable test of all dual task conditions was the 'vigilance walk', who showed the highest correlation in both groups for combined (and motor) DTC, but not for cognitive DTC. There were no clear and systematic differences on reliability between the MS and HC group.