Dual Cognitive, Motor Tasks More Difficult Even in Early MS Stages

Even in early stages of disease, people with multiple sclerosis (MS) commonly experience more difficulties performing cognitive and motor tasks simultaneously than do people without MS, a new study indicates.

The study, “Cognitive-motor interference in people with mild to moderate multiple sclerosis, in comparison with healthy controls,” was published in Multiple Sclerosis and Related Disorders.

Cognitive-motor interference, or CMI, refers to a phenomenon where simultaneously performing motor and cognitive tasks — for example, walking while answering trivia questions — is more problematic than either task on its own.

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An emerging body of research is exploring how CMI manifests in people with MS and how this affects life quality, especially at more advanced stages of disease. How cognitive-motor interference affects people in earlier MS stages, however, and how this compares to CMI in people without the neurological disorder, remain incompletely understood.

Cognitive problems particularly noted when MS patients walking

Scientists in Sweden conducted CMI assessments on 55 people with MS and 30 without the disease (controls). The MS patients were divided into two groups: 28 with mild MS — defined as a score of 2 to 3.5 on the Expanded Disability Status Scale (EDSS) — and 27 with moderate MS (EDSS scores of 4 to 5.5).

Participants all underwent two physical tasks: one where they had to stand still with their eyes closed for about 30 seconds, and another where they walked at a comfortable speed for about two minutes. In both tasks, worn sensors were used to detect relevant measures (e.g., swaying in the standing task or stride speed in the walking task).

They also completed a cognitive task in which an auditory tone was played at either high or low pitch. The tone would say the words “high” or “low,” but the word and the actual tone did not always match up. Participants had to say whether the tone itself was high or low, ignoring the word given, and they were scored based on their accuracy and speed.

The participants completed each of these tasks separately (single task). Then, they completed each of the motor tasks again while simultaneously doing the cognitive task (dual task).

“For exploration of CMI, we used a cognitive task that challenges executive functions and involves conflicting stimuli,” the researchers wrote.

Across all the groups, there were notable differences in outcomes between the single-task and dual-task scenarios. For example, during the standing task, all groups tended to sway less when they were also doing the cognitive task. In the walking test, significant reductions in speed and stride length were recorded during the dual-task condition.

Across virtually all dual-task measures, people with moderate MS performed more poorly than those with mild MS or people without MS. For example, in the dual-task walking test, moderate MS patients walked significantly slower, with markedly shorter steps and more time between each step. Moderate MS patients also had longer delays in responses under both dual-task setups.

“The results imply that an increased level of overall MS-disability is associated with a greater deterioration of motor-cognitive dual-task capacity,” the scientists wrote.

Mild MS patients performed comparably to healthy controls in the walking dual-task setup. In the standing test, however, both MS groups swayed more than healthy controls under dual-task conditions.

“In all dual-task conditions, moderate MS performed worse compared to mild MS and HC [healthy controls]. Mild MS also showed worsened performance in dual tasking compared with HC,” the researchers concluded.

These findings show “cognitive-motor interference in people with MS is present also in the early phases of the disease,” they added

Performance on the cognitive task was generally worse during the walking dual-task than the standing task. While this effect was seen in all of the groups, it was about three times stronger among patients with MS, the researchers noted.

“This indicates that the cognitive task is negatively affected when performing the dual-task in walking in comparison to standing within PwMS [people with MS] but not within the healthy population,” the researchers wrote. “This might result from automaticity, i.e., that motor tasks can be performed automatically within a healthy population, but that they require greater processing resources in PwMS.”

Exploratory analyses showed that patients with signs of cognitive problems, assessed by the Montreal Cognitive Assessment (MoCA), performed more poorly on the cognitive outcomes in both dual-task setups. The researchers highlighted a need to further explore how standard cognition measures are related to CMI, both in general and in MS specifically.

“Further, development of specific training interventions for improved motor and cognitive dual-task ability among PwMS are needed,” they wrote.