Background
Cognitive impairment is a major debilitating feature of multiple sclerosis, and is estimated to occur in more than 50% of people living with MS at some point during the disease. These cognitive impairments can appear as difficulties with learning and memory, and deterioration of executive functions, such as planning or decision-making, focusing attention, multi-tasking, and problem-solving. People living with cognitive deficits can experience greatly diminished quality of life and loss of independence while facing the realization that treatment options are few-and-far-between. There are currently no drug therapies available that can specifically treat cognitive impairments in people living with MS, and cognitive rehabilitation studies have shown mixed success to date.
One approach that is emerging as a promising strategy for treating cognitive dysfunction in MS is exercise training. There is compelling experimental evidence showing that specific types of exercise training can improve cognition in both the general population and in people with certain neurological conditions like stroke, traumatic brain injury, and schizophrenia. For people living with MS, there have been three controlled clinical trials that have examined the effects of exercise on some aspects of cognition, although the results so far have been mixed. Part of the reason for these inconclusive findings is that the types and intensities of exercise have yet to be standardized, making comparisons across studies difficult.
A study published in the Journal of Clinical and Experimental Neuropsychology by Dr. Robert Motl and colleagues examined the short-term effects of several types of aerobic and non-aerobic exercise training on cognitive performance in people living with relapsing-remitting MS.
The Study
The study was performed on 24 individuals with relapsing-remitting MS. The participants underwent assessment of disability status using the Expanded Disability Status Scale (EDSS); eligible participants needed to be able to walk with or without minimal assistance (e.g. cane or crutch) in order to be able to participate in the exercise routines.
The researchers used the modified-flanker test (click here to take the test) to assess each subject’s reaction time and accuracy in identifying a randomly-presented object while blocking out either helpful or distracting information on either side of the object. In other words, the test allowed the researchers to measure the participants’ attention and executive functions (i.e. ability to suppress information that is either related or unrelated to the task).
The procedure consisted of five sessions (one per week); the first session established the baseline for exercise endurance fitness and trained the participants in the modified-flanker test, and was followed by four testing sessions. For each testing session, participants took the modified-flanker test, followed by one of three exercises (treadmill walking, stationary bicycle, or guided yoga) or quiet rest. After completion of the exercise and a cool-down period, participants took the modified-flanker test again to determine whether the exercise training affected performance on the test. For each session, participants performed a different exercise, so that by the end of the experiment each participant performed every exercise in a random order.
Results
The researchers measured the effects of each type of exercise on participants’ performance in the modified-flanker test, and compared that to their performance after quiet rest. They found that treadmill walking improved reaction time on the test with no improvement in accuracy compared to quiet rest; the reaction time was particularly improved in trials where the target object was surrounded by distracting information.
Both stationary bicycling and guided yoga also improved test reaction time without improving accuracy compared to quiet rest, although the reaction time improvements were not seen in trials where the target object was surrounded by distracting information.
Comment
The results of this study show that several types of exercise can improve cognitive performance and executive functions in people with relapsing-remitting MS. Treadmill walking in particular appeared to have the strongest effect on improving selective attention and blocking distracting information in this study; although the reason for this is unclear, the authors suggested that since impaired ambulation is so common in people with MS, treadmill walking perhaps stimulates those parts of the brain involved in attention to a greater degree than stationary cycling or yoga. The improvements in test performance were only seen in reaction time and not accuracy, although accuracy scores at baseline were already quite high, so there was very little room for improvement. A limitation of this study was that overall, the participants were not cognitively impaired, and it remains to be seen how people affected by MS with cognitive impairment could benefit from exercise training, as well as how to adapt exercise training in those with severe physical disability who cannot carry out these exercises.
The findings from this study contribute to a growing body of literature linking physical activity to neuroplasticity in the brain, both in the general population and in people living with MS. While the bulk of this research has looked at ways of harnessing neuroplasticity for promoting physical rehabilitation, an emerging area of study is the application of exercise interventions to improving cognitive impairment. Visit the research blog to learn more about neuroplasticity in MS.
Source
Sandroff BM et al. (2015) Acute effects of walking, cycling, and yoga exercise on cognition in persons with relapsing-remitting multiple sclerosis without impaired cognitive processing speed. J Clin Exp Neuropsychol. 37(2):209-19