Balance control in people with multiple sclerosis : mechanisms, experiences, design and feasibility of an exercise trial

Abstract

Background: Everyday living entails navigating complex environments and perform-ing activities often requiring simultaneous motor and cognitive actions/tasks (dual-tasking). Disease-related impairments in people with multiple sclerosis (MS) often impact sensorimotor and cognitive functions, both of which may contribute to a vicious cycle of decreased mobility, muscular weakness, impaired balance control, walking limitation, falls, and fall-related injuries. Reduced dual-task capacity is suggested to be more common among people with MS compared with healthy controls, which in turn might impact balance control. A more detailed understanding of the underlying mechanisms contributing to impaired balance control, as well as the experiences of how this affects activities and participation in people with MS’ everyday lives, is still lacking. Furthermore, balance training interventions with a gradual progression of difficulty and highly challenging tasks designed specifically for people with MS are rare. To develop a balance training intervention specifically targeting balance and walking problems for people with MS, both quantitative and qualitative preparatory studies are needed.

Aim of thesis: To explore mechanisms, explore and describe experiences of balance control in people with MS, and furthermore to design and evaluate the feasibility of a highly challenging balance training intervention specific to MS.

Methods: This thesis consists of four papers based on three data collections, including people with mild to moderate overall MS disability and healthy controls. Paper I was a test–retest reliability study of a balance assessment scale, the mini-BESTest, with repeated measurements one week apart; 54 people with MS were included. Paper II was a case-control study evaluating dual-task performances of the motor tasks standing with eyes closed and walking, and a cognitive task, auditory Stroop; 55 people with MS and 30 healthy controls were included. Paper III was a qualitative interview study exploring how impaired balance control affects participation in activities in people with MS’ everyday life; 16 people with MS were included. Paper IV was a single-group feasibility trial of a balance training intervention developed specifically for MS through a co-design workshop series with stakeholder involvement; 12 people with MS were included.

Results: Paper I showed that the mini-BESTest total score is reliable for assessment of balance control in people with mild to moderate MS over time, and that section and item scores are useful for identification of specific aspects of balance impairment. Paper II demonstrated interference on walking during motor and cognitive dual-tasking both in people with MS and in healthy controls; but only people with mild MS displayed cognitive interference during walking. No dual-task effects were shown dur-ing standing. People with moderate MS performed worse in almost every aspect of dual-tasking compared to those with mild MS and healthy controls. The association between degree of motor–cognitive dual-task interference and an increased level of overall MS disability was evident. People with moderate MS differed significantly from the other groups in walking slower and using longer response time. In Paper III, people with MS described that balance impairment limited and affected performance and participation in everyday activities. The ability to be continuously active was often limited due to lack of energy and to day-to-day variation in capacity. Specific strategies were used when negotiating between capacity and ambition aiming to minimise the impact of balance impairment to keep up a good life. In Paper IV, most aspects of the developed balance training intervention were found to be feasible. However, some adaptations need to be considered to improve retention and training session attend-ance before embarking on a full-scale trial.

Conclusion: The mini-BESTest demonstrated good to excellent test–retest reliability and small measurement errors, and is recommended for use in people with mild to moderate MS. Cognitive–motor interference was also present in people with mild MS. People with moderate MS performed worse than those with mild MS, and healthy controls in almost every aspect of the motor and cognitive dual-task assessments. Furthermore, people with mild to moderate MS perceived balance control as a skill, which, in contrast to their experiences prior to MS onset, has lost its automaticity and requires specific attention and awareness. To maintain everyday function and quality of life, they implement various compensatory strategies. Finally, despite some concerns regarding retention and attendance, the overall trial design and delivery of the designed intervention was found to be feasible for a full-scale trial.