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Background: Performing cognitive–motor dual tasks (DTs) may result in reduced walking speed and cognitive performance. The effect in persons with progressive multiple sclerosis (pwPMS) having cognitive dysfunction is unknown. Objective: To profile DT-performance during walking in cognitively impaired pwPMS and examine DT-performance by disability level. Methods: Secondary analyses were conducted on baseline data from the CogEx-study. Participants, enrolled with Symbol Digit Modalities Test 1.282 standard deviations below normative value, performed a cognitive single task ([ST], alternating alphabet), motor ST (walking) and DT (both). Outcomes were number of correct answers on the alternating alphabet task, walking speed, and DT-cost (DTC: decline in performance relative to the ST). Outcomes were compared between EDSS subgroups (≤ 4, 4.5–5.5, ≥ 6). Spearman correlations were conducted between the DTCmotor with clinical measures. Adjusted significance level was 0.01. Results: Overall, participants (n = 307) walked slower and had fewer correct answers on the DT versus ST (both p < 0.001), with a DTCmotor of 15.8% and DTCcognitive of 2.7%. All three subgroups walked slower during the DT versus ST, with DTCmotor different from zero (p’s < 0.001). Only the EDSS ≥ 6 group had fewer correct answers on the DT versus ST (p < 0.001), but the DTCcognitive did not differ from zero for any of the groups (p ≥ 0.039). Conclusion: Dual tasking substantially affects walking performance in cognitively impaired pwPMS, to a similar degree for EDSS subgroups.

Pandemic restrictions have led to changes in therapy plans and disrupted rehabilitation services for people with multiple sclerosis. CogEx is an international, multicentre MS dual-intervention (cognitive rehabilitation, aerobic exercise) randomized, controlled rehabilitation trial confined to people with progressive disease. The primary outcome is cognition (processing speed).There are 11 treatment sites in six countries with participants required to make 27 site visits over 12 weeks. Collectively, the large, in-person demands of the trial, and the varying international policies for the containment of COVID-19, might disproportionately impact the administration of CogEx. During the first lockdown, all centres closed on average for 82.9 (SD = 24.3) days. One site was required to lockdown on two further occasions. One site remained closed for 16 months. Ten staff (19.2%) were required to quarantine and eight staff (15.4%) tested positive for COVID. 10 of 264 (3.8%) participants acquired COVID-19. All survived. The mean duration of enrollment delay has been [236.7 (SD = 214.5) days]. Restarting participants whose interventions were interrupted by the pandemic meant recalculating the intervention prescriptions for these individuals. While the impact of the pandemic on CogEx has been considerable, all study sites are again open. Participants and staff have shown considerable flexibility and resilience in keeping a complex, international endeavour running. The future in general remains uncertain in the midst of a pandemic, but there is cautious optimism the study will be completed with sufficient sample size to robustly evaluate our hypothesis and provide meaningful results to the MS community on the impact of these interventions on people with progressive MS. Trial registration: The trial was registered on September 20th 2018 at www.clinicaltrials.gov having identifier NCT03679468. Registration was performed before recruitment was initiated.

Background: Aerobic exercise training (physical activity for improving cardiorespiratory fitness) represents a promising approach for managing cognitive impairment in multiple sclerosis (MS). However, there is limited evidence that levels of physical activity and fitness are associated with cognition in progressive MS. Objective: We examined associations among cardiorespiratory fitness, moderate-to-vigorous physical activity (MVPA), and cognitive performance in a large, international progressive MS sample. Methods: Two hundred forty European and North American persons with progressive MS underwent cardiorespiratory fitness measurement on a recumbent stepper, wore an ActiGraph GT3X + accelerometer for 7 days for measuring MVPA, and underwent the Brief International Cognitive Assessment in MS. Results: Cardiorespiratory fitness was not significantly correlated with Symbol Digit Modalities Test (SDMT; r = −0.01; r = −0.04), California Verbal Learning Test-II (CVLT-II; r = 0.05; r = 0.05), or Brief Visuospatial Memory Test–Revised (BVMT-R; r = −0.14; r = −0.14) z-scores controlling for age, sex, and education. MVPA and SDMT ( r = 0.05), CVLT-II ( r = −0.07), and BVMT-R ( r = 0.01) z-scores were not significantly correlated. Conclusion: Cardiorespiratory fitness and MVPA were not associated with cognition in this large progressive MS sample, yet these outcomes represent critical manipulation checks for documenting the success of the CogEx trial. This highlights the importance of examining other exercise-related mechanisms-of-action for improving cognition in progressive MS.