Trying to do two things at once will slow anyone down. However, this twofold action poses an even greater risk to those living with multiple sclerosis.
Trying to multitask is enough to slow down anyone. However, this twofold action poses an even greater risk to multiple sclerosis (MS) patients: the risk of cognitive impairment. The impairment can be caused by shifting from one task to two tasks, known as the dual-task cost.
It has been found that 90% of individuals with MS experience walking difficulties within the first decade following diagnosis. At the same time, 40-70% of these individuals also experience cognitive difficulties, which affect everyday living and therefore, quality of life.
A recent study out of Spain aimed to assess cognitive impairment in an attempt to provide better insights into the lives of those living with MS.
Looking at dual aspects
The researchers involved in the study measured the impact of cognitive-motor interference as a tool for assessing patients with MS. They found the most sensitive variables to be pace, speed, and double support. “The study of cognitive-motor interference focuses on the idea that real-life activity requires a motor component and a cognitive component. For example, you don’t just walk in a straight line. You walk to the store or you walk to school. This requires motor patterns as well as executive function” said Kathy M. Zackowski, senior director of patient management at the National Multiple Sclerosis Society.
Yet, multiple studies have only focused on one of these components, either motor or cognitive, and interventions are often targeted at improving that component but not both. This particular study aimed to learn more about how motor and cognitive impairments interact so that more effective rehabilitation interventions can be introduced.
When asked to multitask, the researchers noticed that the patients with MS showed significant problems associated with cognitive impairment. “One finding was that gait speed is very sensitive to cognitive interference” said Prue Plummer, associate professor of physical therapy at the University of North Chapel at Chapel Hill. However, what distinguished the patients with MS from the patients in good health was that they had to have both feet on the ground for a longer period of time. This is known as double limb support. “Both feet on the ground balances you but slows you down. Healthy people slow down but not going to two-foot walking” said Plummer.
A new area of research
In the study, the researchers reviewed 1540 articles and used 31 for analyses. They separated the cognitive tasks by type and the main ones given were:
- Counting backwards - asking a patient to count numbers backwards while walking
- Verbal fluency - asking a patient to list all vegetables and fruits starting with a specific letter in 1 minute while walking
- Alternate letters of the alphabet – asking a patient to cite alternate letters of the alphabet while walking
- Serial subtracting – asking a patient to start at 100 and then continuously subtract 7, while stating the answer and walking at the same time
The researchers observed that counting backward was not challenging enough to identify any walking difficulties. However, both the tasks involving alternate letters of the alphabet and serial subtracting revealed sensitivity to impairment for both the patients with MS and the patients in good health. What’s more, verbal fluency was sensitive and specific to impairment only for the patients with MS.
All of the tasks required using a certain area of the brain, known as the frontal cortex. The researchers found that this specific area was more susceptible to cognitive impairment among patients with MS. “We know cognitive function affects walking. There is not strong evidence that it is related to more falls. But it slows down walking and affects quality of life and might have implications for safety” said Plummer. “We can’t tell people to not walk and talk. So, improving cognitive tasks in supervised therapy can have some benefits” she added.
As a result of the study, Plummer went on to discuss potential options that could be implemented in clinical practice. For safety, she advised that practicing cognitive skills while walking should be supervised. Moreover, healthcare professionals should help to make patients more aware of what is happening while they are walking, and as a result, help them to become more vigilant.
The role of depression and physical disability
Another recent study found that multitasking is the cognitive ability that is mostly associated with depression in patients with MS.
The researchers involved in the study aimed to assess whether impaired cognitive performance among MS patients with depression was the result of multitasking. They used traditional neuropsychological tasks to assess attention and processing speed, verbal frequency, episodic memory, and working memory. Using stepwise regression, they sought to identify which of the aforementioned tasks predicted level of depression (no symptoms, minimal symptoms, or at least mild symptoms) and found that worse multitasking was seen among the patients with at least mild symptoms versus no symptoms.
After extensive research, the researchers concluded that depression affects individuals with MS-related cognitive impairment, supporting evidence that depressed mood drains available attentional resources. They found that apart from multitasking, no other task predicted level of depression as much.
Improving approaches to treatment development
The presence of cognitive impairment in patients with MS was observed more than 165 years ago. However, it took medical experts until 2001 to implement a standard test for measuring cognitive function. Now, cognitive impairment is seen in up to 70% of individuals with MS and usually diminishes their ability to multitask and recall previously learned information.
While multiple disease modifying treatments aimed at reducing the frequency of clinical exacerbations in MS and improving walking ability have been approved by the FDA, no clinical trials have been successful on targeting and treating cognitive impairment often seen in patients with MS. Nevertheless, greater awareness of cognitive impairment in MS is improving among researchers, healthcare professionals, and patients. Additionally, researchers remain optimistic that new approaches could lead to effective treatment options down the road. “The MS community needs to push scientists to study mechanisms that explain why movements and cognition fail in MS. This is key to the development of more effective rehabilitative interventions” said Kathy Costello, vice president of healthcare access for the National Multiple Sclerosis Society.